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![Helge Deller](/assets/img/avatar_default.png)
commit87ab9f6b74
upstream. This reverts commit39aead8373
. Revert the first (of 2) commits which disabled scrolling acceleration in fbcon/fbdev. It introduced a regression for fbdev-supported graphic cards because of the performance penalty by doing screen scrolling by software instead of using the existing graphic card 2D hardware acceleration. Console scrolling acceleration was disabled by dropping code which checked at runtime the driver hardware capabilities for the BINFO_HWACCEL_COPYAREA or FBINFO_HWACCEL_FILLRECT flags and if set, it enabled scrollmode SCROLL_MOVE which uses hardware acceleration to move screen contents. After dropping those checks scrollmode was hard-wired to SCROLL_REDRAW instead, which forces all graphic cards to redraw every character at the new screen position when scrolling. This change effectively disabled all hardware-based scrolling acceleration for ALL drivers, because now all kind of 2D hardware acceleration (bitblt, fillrect) in the drivers isn't used any longer. The original commit message mentions that only 3 DRM drivers (nouveau, omapdrm and gma500) used hardware acceleration in the past and thus code for checking and using scrolling acceleration is obsolete. This statement is NOT TRUE, because beside the DRM drivers there are around 35 other fbdev drivers which depend on fbdev/fbcon and still provide hardware acceleration for fbdev/fbcon. The original commit message also states that syzbot found lots of bugs in fbcon and thus it's "often the solution to just delete code and remove features". This is true, and the bugs - which actually affected all users of fbcon, including DRM - were fixed, or code was dropped like e.g. the support for software scrollback in vgacon (commit973c096f6a
). So to further analyze which bugs were found by syzbot, I've looked through all patches in drivers/video which were tagged with syzbot or syzkaller back to year 2005. The vast majority fixed the reported issues on a higher level, e.g. when screen is to be resized, or when font size is to be changed. The few ones which touched driver code fixed a real driver bug, e.g. by adding a check. But NONE of those patches touched code of either the SCROLL_MOVE or the SCROLL_REDRAW case. That means, there was no real reason why SCROLL_MOVE had to be ripped-out and just SCROLL_REDRAW had to be used instead. The only reason I can imagine so far was that SCROLL_MOVE wasn't used by DRM and as such it was assumed that it could go away. That argument completely missed the fact that SCROLL_MOVE is still heavily used by fbdev (non-DRM) drivers. Some people mention that using memcpy() instead of the hardware acceleration is pretty much the same speed. But that's not true, at least not for older graphic cards and machines where we see speed decreases by factor 10 and more and thus this change leads to console responsiveness way worse than before. That's why the original commit is to be reverted. By reverting we reintroduce hardware-based scrolling acceleration and fix the performance regression for fbdev drivers. There isn't any impact on DRM when reverting those patches. Signed-off-by: Helge Deller <deller@gmx.de> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> Acked-by: Sven Schnelle <svens@stackframe.org> Cc: stable@vger.kernel.org # v5.10+ Signed-off-by: Helge Deller <deller@gmx.de> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/20220202135531.92183-3-deller@gmx.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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677 lines
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.. _todo:
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=========
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TODO list
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=========
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This section contains a list of smaller janitorial tasks in the kernel DRM
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graphics subsystem useful as newbie projects. Or for slow rainy days.
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Difficulty
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----------
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To make it easier task are categorized into different levels:
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Starter: Good tasks to get started with the DRM subsystem.
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Intermediate: Tasks which need some experience with working in the DRM
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subsystem, or some specific GPU/display graphics knowledge. For debugging issue
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it's good to have the relevant hardware (or a virtual driver set up) available
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for testing.
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Advanced: Tricky tasks that need fairly good understanding of the DRM subsystem
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and graphics topics. Generally need the relevant hardware for development and
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testing.
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Subsystem-wide refactorings
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===========================
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Remove custom dumb_map_offset implementations
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---------------------------------------------
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All GEM based drivers should be using drm_gem_create_mmap_offset() instead.
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Audit each individual driver, make sure it'll work with the generic
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implementation (there's lots of outdated locking leftovers in various
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implementations), and then remove it.
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Contact: Daniel Vetter, respective driver maintainers
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Level: Intermediate
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Convert existing KMS drivers to atomic modesetting
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--------------------------------------------------
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3.19 has the atomic modeset interfaces and helpers, so drivers can now be
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converted over. Modern compositors like Wayland or Surfaceflinger on Android
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really want an atomic modeset interface, so this is all about the bright
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future.
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There is a conversion guide for atomic and all you need is a GPU for a
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non-converted driver (again virtual HW drivers for KVM are still all
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suitable).
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As part of this drivers also need to convert to universal plane (which means
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exposing primary & cursor as proper plane objects). But that's much easier to
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do by directly using the new atomic helper driver callbacks.
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Contact: Daniel Vetter, respective driver maintainers
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Level: Advanced
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Clean up the clipped coordination confusion around planes
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---------------------------------------------------------
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We have a helper to get this right with drm_plane_helper_check_update(), but
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it's not consistently used. This should be fixed, preferrably in the atomic
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helpers (and drivers then moved over to clipped coordinates). Probably the
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helper should also be moved from drm_plane_helper.c to the atomic helpers, to
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avoid confusion - the other helpers in that file are all deprecated legacy
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helpers.
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Contact: Ville Syrjälä, Daniel Vetter, driver maintainers
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Level: Advanced
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Improve plane atomic_check helpers
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----------------------------------
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Aside from the clipped coordinates right above there's a few suboptimal things
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with the current helpers:
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- drm_plane_helper_funcs->atomic_check gets called for enabled or disabled
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planes. At best this seems to confuse drivers, worst it means they blow up
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when the plane is disabled without the CRTC. The only special handling is
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resetting values in the plane state structures, which instead should be moved
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into the drm_plane_funcs->atomic_duplicate_state functions.
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- Once that's done, helpers could stop calling ->atomic_check for disabled
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planes.
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- Then we could go through all the drivers and remove the more-or-less confused
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checks for plane_state->fb and plane_state->crtc.
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Contact: Daniel Vetter
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Level: Advanced
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Convert early atomic drivers to async commit helpers
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----------------------------------------------------
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For the first year the atomic modeset helpers didn't support asynchronous /
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nonblocking commits, and every driver had to hand-roll them. This is fixed
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now, but there's still a pile of existing drivers that easily could be
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converted over to the new infrastructure.
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One issue with the helpers is that they require that drivers handle completion
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events for atomic commits correctly. But fixing these bugs is good anyway.
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Contact: Daniel Vetter, respective driver maintainers
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Level: Advanced
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Fallout from atomic KMS
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-----------------------
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``drm_atomic_helper.c`` provides a batch of functions which implement legacy
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IOCTLs on top of the new atomic driver interface. Which is really nice for
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gradual conversion of drivers, but unfortunately the semantic mismatches are
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a bit too severe. So there's some follow-up work to adjust the function
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interfaces to fix these issues:
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* atomic needs the lock acquire context. At the moment that's passed around
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implicitly with some horrible hacks, and it's also allocate with
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``GFP_NOFAIL`` behind the scenes. All legacy paths need to start allocating
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the acquire context explicitly on stack and then also pass it down into
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drivers explicitly so that the legacy-on-atomic functions can use them.
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Except for some driver code this is done. This task should be finished by
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adding WARN_ON(!drm_drv_uses_atomic_modeset) in drm_modeset_lock_all().
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* A bunch of the vtable hooks are now in the wrong place: DRM has a split
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between core vfunc tables (named ``drm_foo_funcs``), which are used to
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implement the userspace ABI. And then there's the optional hooks for the
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helper libraries (name ``drm_foo_helper_funcs``), which are purely for
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internal use. Some of these hooks should be move from ``_funcs`` to
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``_helper_funcs`` since they are not part of the core ABI. There's a
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``FIXME`` comment in the kerneldoc for each such case in ``drm_crtc.h``.
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Contact: Daniel Vetter
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Level: Intermediate
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Get rid of dev->struct_mutex from GEM drivers
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---------------------------------------------
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``dev->struct_mutex`` is the Big DRM Lock from legacy days and infested
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everything. Nowadays in modern drivers the only bit where it's mandatory is
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serializing GEM buffer object destruction. Which unfortunately means drivers
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have to keep track of that lock and either call ``unreference`` or
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``unreference_locked`` depending upon context.
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Core GEM doesn't have a need for ``struct_mutex`` any more since kernel 4.8,
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and there's a ``gem_free_object_unlocked`` callback for any drivers which are
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entirely ``struct_mutex`` free.
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For drivers that need ``struct_mutex`` it should be replaced with a driver-
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private lock. The tricky part is the BO free functions, since those can't
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reliably take that lock any more. Instead state needs to be protected with
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suitable subordinate locks or some cleanup work pushed to a worker thread. For
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performance-critical drivers it might also be better to go with a more
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fine-grained per-buffer object and per-context lockings scheme. Currently only
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the ``msm`` and `i915` drivers use ``struct_mutex``.
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Contact: Daniel Vetter, respective driver maintainers
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Level: Advanced
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Convert logging to drm_* functions with drm_device paramater
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------------------------------------------------------------
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For drivers which could have multiple instances, it is necessary to
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differentiate between which is which in the logs. Since DRM_INFO/WARN/ERROR
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don't do this, drivers used dev_info/warn/err to make this differentiation. We
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now have drm_* variants of the drm print functions, so we can start to convert
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those drivers back to using drm-formatted specific log messages.
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Before you start this conversion please contact the relevant maintainers to make
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sure your work will be merged - not everyone agrees that the DRM dmesg macros
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are better.
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Contact: Sean Paul, Maintainer of the driver you plan to convert
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Level: Starter
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Convert drivers to use simple modeset suspend/resume
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----------------------------------------------------
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Most drivers (except i915 and nouveau) that use
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drm_atomic_helper_suspend/resume() can probably be converted to use
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drm_mode_config_helper_suspend/resume(). Also there's still open-coded version
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of the atomic suspend/resume code in older atomic modeset drivers.
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Contact: Maintainer of the driver you plan to convert
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Level: Intermediate
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Convert drivers to use drm_fbdev_generic_setup()
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------------------------------------------------
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Most drivers can use drm_fbdev_generic_setup(). Driver have to implement
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atomic modesetting and GEM vmap support. Current generic fbdev emulation
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expects the framebuffer in system memory (or system-like memory).
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Contact: Maintainer of the driver you plan to convert
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Level: Intermediate
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drm_framebuffer_funcs and drm_mode_config_funcs.fb_create cleanup
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-----------------------------------------------------------------
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A lot more drivers could be switched over to the drm_gem_framebuffer helpers.
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Various hold-ups:
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- Need to switch over to the generic dirty tracking code using
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drm_atomic_helper_dirtyfb first (e.g. qxl).
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- Need to switch to drm_fbdev_generic_setup(), otherwise a lot of the custom fb
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setup code can't be deleted.
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- Many drivers wrap drm_gem_fb_create() only to check for valid formats. For
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atomic drivers we could check for valid formats by calling
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drm_plane_check_pixel_format() against all planes, and pass if any plane
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supports the format. For non-atomic that's not possible since like the format
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list for the primary plane is fake and we'd therefor reject valid formats.
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- Many drivers subclass drm_framebuffer, we'd need a embedding compatible
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version of the varios drm_gem_fb_create functions. Maybe called
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drm_gem_fb_create/_with_dirty/_with_funcs as needed.
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Contact: Daniel Vetter
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Level: Intermediate
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Clean up mmap forwarding
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------------------------
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A lot of drivers forward gem mmap calls to dma-buf mmap for imported buffers.
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And also a lot of them forward dma-buf mmap to the gem mmap implementations.
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There's drm_gem_prime_mmap() for this now, but still needs to be rolled out.
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Contact: Daniel Vetter
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Level: Intermediate
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Generic fbdev defio support
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---------------------------
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The defio support code in the fbdev core has some very specific requirements,
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which means drivers need to have a special framebuffer for fbdev. The main
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issue is that it uses some fields in struct page itself, which breaks shmem
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gem objects (and other things). To support defio, affected drivers require
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the use of a shadow buffer, which may add CPU and memory overhead.
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Possible solution would be to write our own defio mmap code in the drm fbdev
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emulation. It would need to fully wrap the existing mmap ops, forwarding
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everything after it has done the write-protect/mkwrite trickery:
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- In the drm_fbdev_fb_mmap helper, if we need defio, change the
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default page prots to write-protected with something like this::
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vma->vm_page_prot = pgprot_wrprotect(vma->vm_page_prot);
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- Set the mkwrite and fsync callbacks with similar implementions to the core
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fbdev defio stuff. These should all work on plain ptes, they don't actually
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require a struct page. uff. These should all work on plain ptes, they don't
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actually require a struct page.
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- Track the dirty pages in a separate structure (bitfield with one bit per page
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should work) to avoid clobbering struct page.
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Might be good to also have some igt testcases for this.
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Contact: Daniel Vetter, Noralf Tronnes
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Level: Advanced
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idr_init_base()
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---------------
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DRM core&drivers uses a lot of idr (integer lookup directories) for mapping
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userspace IDs to internal objects, and in most places ID=0 means NULL and hence
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is never used. Switching to idr_init_base() for these would make the idr more
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efficient.
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Contact: Daniel Vetter
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Level: Starter
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struct drm_gem_object_funcs
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---------------------------
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GEM objects can now have a function table instead of having the callbacks on the
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DRM driver struct. This is now the preferred way and drivers can be moved over.
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We also need a 2nd version of the CMA define that doesn't require the
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vmapping to be present (different hook for prime importing). Plus this needs to
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be rolled out to all drivers using their own implementations, too.
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Level: Intermediate
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Use DRM_MODESET_LOCK_ALL_* helpers instead of boilerplate
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---------------------------------------------------------
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For cases where drivers are attempting to grab the modeset locks with a local
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acquire context. Replace the boilerplate code surrounding
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drm_modeset_lock_all_ctx() with DRM_MODESET_LOCK_ALL_BEGIN() and
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DRM_MODESET_LOCK_ALL_END() instead.
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This should also be done for all places where drm_modeset_lock_all() is still
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used.
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As a reference, take a look at the conversions already completed in drm core.
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Contact: Sean Paul, respective driver maintainers
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Level: Starter
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Rename CMA helpers to DMA helpers
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---------------------------------
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CMA (standing for contiguous memory allocator) is really a bit an accident of
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what these were used for first, a much better name would be DMA helpers. In the
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text these should even be called coherent DMA memory helpers (so maybe CDM, but
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no one knows what that means) since underneath they just use dma_alloc_coherent.
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Contact: Laurent Pinchart, Daniel Vetter
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Level: Intermediate (mostly because it is a huge tasks without good partial
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milestones, not technically itself that challenging)
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connector register/unregister fixes
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-----------------------------------
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- For most connectors it's a no-op to call drm_connector_register/unregister
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directly from driver code, drm_dev_register/unregister take care of this
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already. We can remove all of them.
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- For dp drivers it's a bit more a mess, since we need the connector to be
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registered when calling drm_dp_aux_register. Fix this by instead calling
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drm_dp_aux_init, and moving the actual registering into a late_register
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callback as recommended in the kerneldoc.
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Level: Intermediate
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Remove load/unload callbacks from all non-DRIVER_LEGACY drivers
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---------------------------------------------------------------
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The load/unload callbacks in struct &drm_driver are very much midlayers, plus
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for historical reasons they get the ordering wrong (and we can't fix that)
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between setting up the &drm_driver structure and calling drm_dev_register().
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- Rework drivers to no longer use the load/unload callbacks, directly coding the
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load/unload sequence into the driver's probe function.
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- Once all non-DRIVER_LEGACY drivers are converted, disallow the load/unload
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callbacks for all modern drivers.
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Contact: Daniel Vetter
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Level: Intermediate
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Replace drm_detect_hdmi_monitor() with drm_display_info.is_hdmi
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---------------------------------------------------------------
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Once EDID is parsed, the monitor HDMI support information is available through
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drm_display_info.is_hdmi. Many drivers still call drm_detect_hdmi_monitor() to
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retrieve the same information, which is less efficient.
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Audit each individual driver calling drm_detect_hdmi_monitor() and switch to
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drm_display_info.is_hdmi if applicable.
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Contact: Laurent Pinchart, respective driver maintainers
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Level: Intermediate
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Consolidate custom driver modeset properties
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--------------------------------------------
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Before atomic modeset took place, many drivers where creating their own
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properties. Among other things, atomic brought the requirement that custom,
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driver specific properties should not be used.
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For this task, we aim to introduce core helpers or reuse the existing ones
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if available:
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A quick, unconfirmed, examples list.
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Introduce core helpers:
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- audio (amdgpu, intel, gma500, radeon)
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- brightness, contrast, etc (armada, nouveau) - overlay only (?)
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- broadcast rgb (gma500, intel)
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- colorkey (armada, nouveau, rcar) - overlay only (?)
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- dither (amdgpu, nouveau, radeon) - varies across drivers
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- underscan family (amdgpu, radeon, nouveau)
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Already in core:
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- colorspace (sti)
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- tv format names, enhancements (gma500, intel)
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- tv overscan, margins, etc. (gma500, intel)
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- zorder (omapdrm) - same as zpos (?)
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Contact: Emil Velikov, respective driver maintainers
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Level: Intermediate
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Plumb drm_atomic_state all over
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-------------------------------
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Currently various atomic functions take just a single or a handful of
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object states (eg. plane state). While that single object state can
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suffice for some simple cases, we often have to dig out additional
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object states for dealing with various dependencies between the individual
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objects or the hardware they represent. The process of digging out the
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additional states is rather non-intuitive and error prone.
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To fix that most functions should rather take the overall
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drm_atomic_state as one of their parameters. The other parameters
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would generally be the object(s) we mainly want to interact with.
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For example, instead of
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.. code-block:: c
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int (*atomic_check)(struct drm_plane *plane, struct drm_plane_state *state);
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we would have something like
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.. code-block:: c
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int (*atomic_check)(struct drm_plane *plane, struct drm_atomic_state *state);
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The implementation can then trivially gain access to any required object
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state(s) via drm_atomic_get_plane_state(), drm_atomic_get_new_plane_state(),
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drm_atomic_get_old_plane_state(), and their equivalents for
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other object types.
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Additionally many drivers currently access the object->state pointer
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directly in their commit functions. That is not going to work if we
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eg. want to allow deeper commit pipelines as those pointers could
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then point to the states corresponding to a future commit instead of
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the current commit we're trying to process. Also non-blocking commits
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execute locklessly so there are serious concerns with dereferencing
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the object->state pointers without holding the locks that protect them.
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Use of drm_atomic_get_new_plane_state(), drm_atomic_get_old_plane_state(),
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etc. avoids these problems as well since they relate to a specific
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commit via the passed in drm_atomic_state.
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Contact: Ville Syrjälä, Daniel Vetter
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Level: Intermediate
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Core refactorings
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=================
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Make panic handling work
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------------------------
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This is a really varied tasks with lots of little bits and pieces:
|
|
|
|
* The panic path can't be tested currently, leading to constant breaking. The
|
|
main issue here is that panics can be triggered from hardirq contexts and
|
|
hence all panic related callback can run in hardirq context. It would be
|
|
awesome if we could test at least the fbdev helper code and driver code by
|
|
e.g. trigger calls through drm debugfs files. hardirq context could be
|
|
achieved by using an IPI to the local processor.
|
|
|
|
* There's a massive confusion of different panic handlers. DRM fbdev emulation
|
|
helpers have one, but on top of that the fbcon code itself also has one. We
|
|
need to make sure that they stop fighting over each another.
|
|
|
|
* ``drm_can_sleep()`` is a mess. It hides real bugs in normal operations and
|
|
isn't a full solution for panic paths. We need to make sure that it only
|
|
returns true if there's a panic going on for real, and fix up all the
|
|
fallout.
|
|
|
|
* The panic handler must never sleep, which also means it can't ever
|
|
``mutex_lock()``. Also it can't grab any other lock unconditionally, not
|
|
even spinlocks (because NMI and hardirq can panic too). We need to either
|
|
make sure to not call such paths, or trylock everything. Really tricky.
|
|
|
|
* For the above locking troubles reasons it's pretty much impossible to
|
|
attempt a synchronous modeset from panic handlers. The only thing we could
|
|
try to achive is an atomic ``set_base`` of the primary plane, and hope that
|
|
it shows up. Everything else probably needs to be delayed to some worker or
|
|
something else which happens later on. Otherwise it just kills the box
|
|
harder, prevent the panic from going out on e.g. netconsole.
|
|
|
|
* There's also proposal for a simplied DRM console instead of the full-blown
|
|
fbcon and DRM fbdev emulation. Any kind of panic handling tricks should
|
|
obviously work for both console, in case we ever get kmslog merged.
|
|
|
|
Contact: Daniel Vetter
|
|
|
|
Level: Advanced
|
|
|
|
Clean up the debugfs support
|
|
----------------------------
|
|
|
|
There's a bunch of issues with it:
|
|
|
|
- The drm_info_list ->show() function doesn't even bother to cast to the drm
|
|
structure for you. This is lazy.
|
|
|
|
- We probably want to have some support for debugfs files on crtc/connectors and
|
|
maybe other kms objects directly in core. There's even drm_print support in
|
|
the funcs for these objects to dump kms state, so it's all there. And then the
|
|
->show() functions should obviously give you a pointer to the right object.
|
|
|
|
- The drm_info_list stuff is centered on drm_minor instead of drm_device. For
|
|
anything we want to print drm_device (or maybe drm_file) is the right thing.
|
|
|
|
- The drm_driver->debugfs_init hooks we have is just an artifact of the old
|
|
midlayered load sequence. DRM debugfs should work more like sysfs, where you
|
|
can create properties/files for an object anytime you want, and the core
|
|
takes care of publishing/unpuplishing all the files at register/unregister
|
|
time. Drivers shouldn't need to worry about these technicalities, and fixing
|
|
this (together with the drm_minor->drm_device move) would allow us to remove
|
|
debugfs_init.
|
|
|
|
- Drop the return code and error checking from all debugfs functions. Greg KH is
|
|
working on this already.
|
|
|
|
Contact: Daniel Vetter
|
|
|
|
Level: Intermediate
|
|
|
|
KMS cleanups
|
|
------------
|
|
|
|
Some of these date from the very introduction of KMS in 2008 ...
|
|
|
|
- Make ->funcs and ->helper_private vtables optional. There's a bunch of empty
|
|
function tables in drivers, but before we can remove them we need to make sure
|
|
that all the users in helpers and drivers do correctly check for a NULL
|
|
vtable.
|
|
|
|
- Cleanup up the various ->destroy callbacks. A lot of them just wrapt the
|
|
drm_*_cleanup implementations and can be removed. Some tack a kfree() at the
|
|
end, for which we could add drm_*_cleanup_kfree(). And then there's the (for
|
|
historical reasons) misnamed drm_primary_helper_destroy() function.
|
|
|
|
Level: Intermediate
|
|
|
|
Remove automatic page mapping from dma-buf importing
|
|
----------------------------------------------------
|
|
|
|
When importing dma-bufs, the dma-buf and PRIME frameworks automatically map
|
|
imported pages into the importer's DMA area. drm_gem_prime_fd_to_handle() and
|
|
drm_gem_prime_handle_to_fd() require that importers call dma_buf_attach()
|
|
even if they never do actual device DMA, but only CPU access through
|
|
dma_buf_vmap(). This is a problem for USB devices, which do not support DMA
|
|
operations.
|
|
|
|
To fix the issue, automatic page mappings should be removed from the
|
|
buffer-sharing code. Fixing this is a bit more involved, since the import/export
|
|
cache is also tied to &drm_gem_object.import_attach. Meanwhile we paper over
|
|
this problem for USB devices by fishing out the USB host controller device, as
|
|
long as that supports DMA. Otherwise importing can still needlessly fail.
|
|
|
|
Contact: Thomas Zimmermann <tzimmermann@suse.de>, Daniel Vetter
|
|
|
|
Level: Advanced
|
|
|
|
|
|
Better Testing
|
|
==============
|
|
|
|
Enable trinity for DRM
|
|
----------------------
|
|
|
|
And fix up the fallout. Should be really interesting ...
|
|
|
|
Level: Advanced
|
|
|
|
Make KMS tests in i-g-t generic
|
|
-------------------------------
|
|
|
|
The i915 driver team maintains an extensive testsuite for the i915 DRM driver,
|
|
including tons of testcases for corner-cases in the modesetting API. It would
|
|
be awesome if those tests (at least the ones not relying on Intel-specific GEM
|
|
features) could be made to run on any KMS driver.
|
|
|
|
Basic work to run i-g-t tests on non-i915 is done, what's now missing is mass-
|
|
converting things over. For modeset tests we also first need a bit of
|
|
infrastructure to use dumb buffers for untiled buffers, to be able to run all
|
|
the non-i915 specific modeset tests.
|
|
|
|
Level: Advanced
|
|
|
|
Extend virtual test driver (VKMS)
|
|
---------------------------------
|
|
|
|
See the documentation of :ref:`VKMS <vkms>` for more details. This is an ideal
|
|
internship task, since it only requires a virtual machine and can be sized to
|
|
fit the available time.
|
|
|
|
Contact: Daniel Vetter
|
|
|
|
Level: See details
|
|
|
|
Backlight Refactoring
|
|
---------------------
|
|
|
|
Backlight drivers have a triple enable/disable state, which is a bit overkill.
|
|
Plan to fix this:
|
|
|
|
1. Roll out backlight_enable() and backlight_disable() helpers everywhere. This
|
|
has started already.
|
|
2. In all, only look at one of the three status bits set by the above helpers.
|
|
3. Remove the other two status bits.
|
|
|
|
Contact: Daniel Vetter
|
|
|
|
Level: Intermediate
|
|
|
|
Driver Specific
|
|
===============
|
|
|
|
AMD DC Display Driver
|
|
---------------------
|
|
|
|
AMD DC is the display driver for AMD devices starting with Vega. There has been
|
|
a bunch of progress cleaning it up but there's still plenty of work to be done.
|
|
|
|
See drivers/gpu/drm/amd/display/TODO for tasks.
|
|
|
|
Contact: Harry Wentland, Alex Deucher
|
|
|
|
Bootsplash
|
|
==========
|
|
|
|
There is support in place now for writing internal DRM clients making it
|
|
possible to pick up the bootsplash work that was rejected because it was written
|
|
for fbdev.
|
|
|
|
- [v6,8/8] drm/client: Hack: Add bootsplash example
|
|
https://patchwork.freedesktop.org/patch/306579/
|
|
|
|
- [RFC PATCH v2 00/13] Kernel based bootsplash
|
|
https://lkml.org/lkml/2017/12/13/764
|
|
|
|
Contact: Sam Ravnborg
|
|
|
|
Level: Advanced
|
|
|
|
Outside DRM
|
|
===========
|
|
|
|
Convert fbdev drivers to DRM
|
|
----------------------------
|
|
|
|
There are plenty of fbdev drivers for older hardware. Some hwardware has
|
|
become obsolete, but some still provides good(-enough) framebuffers. The
|
|
drivers that are still useful should be converted to DRM and afterwards
|
|
removed from fbdev.
|
|
|
|
Very simple fbdev drivers can best be converted by starting with a new
|
|
DRM driver. Simple KMS helpers and SHMEM should be able to handle any
|
|
existing hardware. The new driver's call-back functions are filled from
|
|
existing fbdev code.
|
|
|
|
More complex fbdev drivers can be refactored step-by-step into a DRM
|
|
driver with the help of the DRM fbconv helpers. [1] These helpers provide
|
|
the transition layer between the DRM core infrastructure and the fbdev
|
|
driver interface. Create a new DRM driver on top of the fbconv helpers,
|
|
copy over the fbdev driver, and hook it up to the DRM code. Examples for
|
|
several fbdev drivers are available at [1] and a tutorial of this process
|
|
available at [2]. The result is a primitive DRM driver that can run X11
|
|
and Weston.
|
|
|
|
- [1] https://gitlab.freedesktop.org/tzimmermann/linux/tree/fbconv
|
|
- [2] https://gitlab.freedesktop.org/tzimmermann/linux/blob/fbconv/drivers/gpu/drm/drm_fbconv_helper.c
|
|
|
|
Contact: Thomas Zimmermann <tzimmermann@suse.de>
|
|
|
|
Level: Advanced
|