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![Chris Wilson](/assets/img/avatar_default.png)
Forgo the struct_mutex serialisation for i915_active, and interpose its own mutex handling for active/retire. This is a multi-layered sleight-of-hand. First, we had to ensure that no active/retire callbacks accidentally inverted the mutex ordering rules, nor assumed that they were themselves serialised by struct_mutex. More challenging though, is the rule over updating elements of the active rbtree. Instead of the whole i915_active now being serialised by struct_mutex, allocations/rotations of the tree are serialised by the i915_active.mutex and individual nodes are serialised by the caller using the i915_timeline.mutex (we need to use nested spinlocks to interact with the dma_fence callback lists). The pain point here is that instead of a single mutex around execbuf, we now have to take a mutex for active tracker (one for each vma, context, etc) and a couple of spinlocks for each fence update. The improvement in fine grained locking allowing for multiple concurrent clients (eventually!) should be worth it in typical loads. v2: Add some comments that barely elucidate anything :( Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20191004134015.13204-6-chris@chris-wilson.co.uk
317 lines
10 KiB
C
317 lines
10 KiB
C
/*
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* Copyright © 2014 Intel Corporation
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*
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* Authors:
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* Daniel Vetter <daniel.vetter@ffwll.ch>
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*/
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/**
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* DOC: frontbuffer tracking
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*
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* Many features require us to track changes to the currently active
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* frontbuffer, especially rendering targeted at the frontbuffer.
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*
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* To be able to do so we track frontbuffers using a bitmask for all possible
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* frontbuffer slots through intel_frontbuffer_track(). The functions in this
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* file are then called when the contents of the frontbuffer are invalidated,
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* when frontbuffer rendering has stopped again to flush out all the changes
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* and when the frontbuffer is exchanged with a flip. Subsystems interested in
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* frontbuffer changes (e.g. PSR, FBC, DRRS) should directly put their callbacks
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* into the relevant places and filter for the frontbuffer slots that they are
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* interested int.
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*
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* On a high level there are two types of powersaving features. The first one
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* work like a special cache (FBC and PSR) and are interested when they should
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* stop caching and when to restart caching. This is done by placing callbacks
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* into the invalidate and the flush functions: At invalidate the caching must
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* be stopped and at flush time it can be restarted. And maybe they need to know
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* when the frontbuffer changes (e.g. when the hw doesn't initiate an invalidate
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* and flush on its own) which can be achieved with placing callbacks into the
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* flip functions.
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*
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* The other type of display power saving feature only cares about busyness
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* (e.g. DRRS). In that case all three (invalidate, flush and flip) indicate
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* busyness. There is no direct way to detect idleness. Instead an idle timer
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* work delayed work should be started from the flush and flip functions and
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* cancelled as soon as busyness is detected.
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*/
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#include "display/intel_dp.h"
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#include "i915_drv.h"
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#include "intel_display_types.h"
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#include "intel_fbc.h"
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#include "intel_frontbuffer.h"
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#include "intel_psr.h"
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/**
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* frontbuffer_flush - flush frontbuffer
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* @i915: i915 device
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* @frontbuffer_bits: frontbuffer plane tracking bits
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* @origin: which operation caused the flush
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*
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* This function gets called every time rendering on the given planes has
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* completed and frontbuffer caching can be started again. Flushes will get
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* delayed if they're blocked by some outstanding asynchronous rendering.
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*
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* Can be called without any locks held.
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*/
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static void frontbuffer_flush(struct drm_i915_private *i915,
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unsigned int frontbuffer_bits,
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enum fb_op_origin origin)
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{
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/* Delay flushing when rings are still busy.*/
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spin_lock(&i915->fb_tracking.lock);
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frontbuffer_bits &= ~i915->fb_tracking.busy_bits;
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spin_unlock(&i915->fb_tracking.lock);
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if (!frontbuffer_bits)
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return;
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might_sleep();
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intel_edp_drrs_flush(i915, frontbuffer_bits);
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intel_psr_flush(i915, frontbuffer_bits, origin);
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intel_fbc_flush(i915, frontbuffer_bits, origin);
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}
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/**
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* intel_frontbuffer_flip_prepare - prepare asynchronous frontbuffer flip
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* @i915: i915 device
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* @frontbuffer_bits: frontbuffer plane tracking bits
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*
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* This function gets called after scheduling a flip on @obj. The actual
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* frontbuffer flushing will be delayed until completion is signalled with
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* intel_frontbuffer_flip_complete. If an invalidate happens in between this
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* flush will be cancelled.
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*
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* Can be called without any locks held.
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*/
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void intel_frontbuffer_flip_prepare(struct drm_i915_private *i915,
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unsigned frontbuffer_bits)
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{
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spin_lock(&i915->fb_tracking.lock);
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i915->fb_tracking.flip_bits |= frontbuffer_bits;
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/* Remove stale busy bits due to the old buffer. */
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i915->fb_tracking.busy_bits &= ~frontbuffer_bits;
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spin_unlock(&i915->fb_tracking.lock);
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}
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/**
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* intel_frontbuffer_flip_complete - complete asynchronous frontbuffer flip
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* @i915: i915 device
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* @frontbuffer_bits: frontbuffer plane tracking bits
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*
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* This function gets called after the flip has been latched and will complete
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* on the next vblank. It will execute the flush if it hasn't been cancelled yet.
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*
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* Can be called without any locks held.
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*/
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void intel_frontbuffer_flip_complete(struct drm_i915_private *i915,
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unsigned frontbuffer_bits)
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{
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spin_lock(&i915->fb_tracking.lock);
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/* Mask any cancelled flips. */
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frontbuffer_bits &= i915->fb_tracking.flip_bits;
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i915->fb_tracking.flip_bits &= ~frontbuffer_bits;
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spin_unlock(&i915->fb_tracking.lock);
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if (frontbuffer_bits)
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frontbuffer_flush(i915, frontbuffer_bits, ORIGIN_FLIP);
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}
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/**
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* intel_frontbuffer_flip - synchronous frontbuffer flip
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* @i915: i915 device
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* @frontbuffer_bits: frontbuffer plane tracking bits
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*
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* This function gets called after scheduling a flip on @obj. This is for
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* synchronous plane updates which will happen on the next vblank and which will
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* not get delayed by pending gpu rendering.
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*
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* Can be called without any locks held.
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*/
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void intel_frontbuffer_flip(struct drm_i915_private *i915,
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unsigned frontbuffer_bits)
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{
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spin_lock(&i915->fb_tracking.lock);
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/* Remove stale busy bits due to the old buffer. */
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i915->fb_tracking.busy_bits &= ~frontbuffer_bits;
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spin_unlock(&i915->fb_tracking.lock);
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frontbuffer_flush(i915, frontbuffer_bits, ORIGIN_FLIP);
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}
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void __intel_fb_invalidate(struct intel_frontbuffer *front,
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enum fb_op_origin origin,
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unsigned int frontbuffer_bits)
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{
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struct drm_i915_private *i915 = to_i915(front->obj->base.dev);
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if (origin == ORIGIN_CS) {
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spin_lock(&i915->fb_tracking.lock);
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i915->fb_tracking.busy_bits |= frontbuffer_bits;
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i915->fb_tracking.flip_bits &= ~frontbuffer_bits;
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spin_unlock(&i915->fb_tracking.lock);
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}
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might_sleep();
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intel_psr_invalidate(i915, frontbuffer_bits, origin);
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intel_edp_drrs_invalidate(i915, frontbuffer_bits);
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intel_fbc_invalidate(i915, frontbuffer_bits, origin);
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}
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void __intel_fb_flush(struct intel_frontbuffer *front,
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enum fb_op_origin origin,
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unsigned int frontbuffer_bits)
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{
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struct drm_i915_private *i915 = to_i915(front->obj->base.dev);
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if (origin == ORIGIN_CS) {
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spin_lock(&i915->fb_tracking.lock);
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/* Filter out new bits since rendering started. */
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frontbuffer_bits &= i915->fb_tracking.busy_bits;
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i915->fb_tracking.busy_bits &= ~frontbuffer_bits;
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spin_unlock(&i915->fb_tracking.lock);
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}
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if (frontbuffer_bits)
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frontbuffer_flush(i915, frontbuffer_bits, origin);
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}
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static int frontbuffer_active(struct i915_active *ref)
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{
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struct intel_frontbuffer *front =
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container_of(ref, typeof(*front), write);
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kref_get(&front->ref);
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return 0;
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}
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__i915_active_call
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static void frontbuffer_retire(struct i915_active *ref)
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{
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struct intel_frontbuffer *front =
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container_of(ref, typeof(*front), write);
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intel_frontbuffer_flush(front, ORIGIN_CS);
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intel_frontbuffer_put(front);
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}
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static void frontbuffer_release(struct kref *ref)
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__releases(&to_i915(front->obj->base.dev)->fb_tracking.lock)
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{
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struct intel_frontbuffer *front =
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container_of(ref, typeof(*front), ref);
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struct drm_i915_gem_object *obj = front->obj;
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struct i915_vma *vma;
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spin_lock(&obj->vma.lock);
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for_each_ggtt_vma(vma, obj)
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vma->display_alignment = I915_GTT_MIN_ALIGNMENT;
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spin_unlock(&obj->vma.lock);
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obj->frontbuffer = NULL;
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spin_unlock(&to_i915(obj->base.dev)->fb_tracking.lock);
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i915_gem_object_put(obj);
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kfree(front);
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}
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struct intel_frontbuffer *
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intel_frontbuffer_get(struct drm_i915_gem_object *obj)
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{
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struct drm_i915_private *i915 = to_i915(obj->base.dev);
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struct intel_frontbuffer *front;
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spin_lock(&i915->fb_tracking.lock);
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front = obj->frontbuffer;
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if (front)
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kref_get(&front->ref);
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spin_unlock(&i915->fb_tracking.lock);
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if (front)
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return front;
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front = kmalloc(sizeof(*front), GFP_KERNEL);
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if (!front)
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return NULL;
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front->obj = obj;
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kref_init(&front->ref);
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atomic_set(&front->bits, 0);
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i915_active_init(&front->write,
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frontbuffer_active,
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i915_active_may_sleep(frontbuffer_retire));
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spin_lock(&i915->fb_tracking.lock);
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if (obj->frontbuffer) {
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kfree(front);
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front = obj->frontbuffer;
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kref_get(&front->ref);
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} else {
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i915_gem_object_get(obj);
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obj->frontbuffer = front;
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}
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spin_unlock(&i915->fb_tracking.lock);
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return front;
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}
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void intel_frontbuffer_put(struct intel_frontbuffer *front)
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{
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kref_put_lock(&front->ref,
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frontbuffer_release,
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&to_i915(front->obj->base.dev)->fb_tracking.lock);
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}
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/**
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* intel_frontbuffer_track - update frontbuffer tracking
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* @old: current buffer for the frontbuffer slots
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* @new: new buffer for the frontbuffer slots
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* @frontbuffer_bits: bitmask of frontbuffer slots
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*
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* This updates the frontbuffer tracking bits @frontbuffer_bits by clearing them
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* from @old and setting them in @new. Both @old and @new can be NULL.
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*/
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void intel_frontbuffer_track(struct intel_frontbuffer *old,
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struct intel_frontbuffer *new,
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unsigned int frontbuffer_bits)
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{
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/*
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* Control of individual bits within the mask are guarded by
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* the owning plane->mutex, i.e. we can never see concurrent
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* manipulation of individual bits. But since the bitfield as a whole
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* is updated using RMW, we need to use atomics in order to update
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* the bits.
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*/
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BUILD_BUG_ON(INTEL_FRONTBUFFER_BITS_PER_PIPE * I915_MAX_PIPES >
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BITS_PER_TYPE(atomic_t));
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if (old) {
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WARN_ON(!(atomic_read(&old->bits) & frontbuffer_bits));
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atomic_andnot(frontbuffer_bits, &old->bits);
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}
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if (new) {
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WARN_ON(atomic_read(&new->bits) & frontbuffer_bits);
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atomic_or(frontbuffer_bits, &new->bits);
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}
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}
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