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Takashi Iwai 2be79d5864 ALSA: usb-audio: Split endpoint setups for hw_params and prepare (take#2) 
This is a second attempt to fix the bug appearing on Android with the
recent kernel; the first try was ff878b408a and reverted at commit
79764ec772.

The details taken from the v1 patch:

One of the former changes for the endpoint management was the more
consistent setup of endpoints at hw_params.
snd_usb_endpoint_configure() is a single function that does the full
setup, and it's called from both PCM hw_params and prepare callbacks.
Although the EP setup at the prepare phase is usually skipped (by
checking need_setup flag), it may be still effective in some cases
like suspend/resume that requires the interface setup again.

As it's a full and single setup, the invocation of
snd_usb_endpoint_configure() includes not only the USB interface setup
but also the buffer release and allocation.  OTOH, doing the buffer
release and re-allocation at PCM prepare phase is rather superfluous,
and better to be done only in the hw_params phase.

For those optimizations, this patch splits the endpoint setup to two
phases: snd_usb_endpoint_set_params() and snd_usb_endpoint_prepare(),
to be called from hw_params and from prepare, respectively.

Note that this patch changes the driver operation slightly,
effectively moving the USB interface setup again to PCM prepare stage
instead of hw_params stage, while the buffer allocation and such
initializations are still done at hw_params stage.

And, the change of the USB interface setup timing (moving to prepare)
gave an interesting "fix", too: it was reported that the recent
kernels caused silent output at the beginning on playbacks on some
devices on Android, and this change casually fixed the regression.
It seems that those devices are picky about the sample rate change (or
the interface change?), and don't follow the too immediate rate
changes.

Meanwhile, Android operates the PCM in the following order:
- open, then hw_params with the possibly highest sample rate
- close without prepare
- re-open, hw_params with the normal sample rate
- prepare, and start streaming
This procedure ended up the hw_params twice with different rates, and
because the recent kernel did set up the sample rate twice one and
after, it screwed up the device.  OTOH, the earlier kernels didn't set
up the USB interface at hw_params, hence this problem didn't appear.

Now, with this patch, the USB interface setup is again back to the
prepare phase, and it works around the problem automagically.
Although we should address the sample rate problem in a more solid
way in future, let's keep things working as before for now.

***

What's new in the take#2 patch:
- The regression caused by the v1 patch (bko#216500) was due to the
  missing check of need_setup flag at hw_params.  Now the check is
  added, and the snd_usb_endpoint_set_params() call is skipped when
  the running EP is re-opened.

- There was another bug in v1 where the clock reference rate wasn't
  updated at hw_params phase, which may lead to a lack of the proper
  hw constraints when an application doesn't issue the prepare but
  only the hw_params call.  This patch fixes it as well by tracking
  the clock rate change in the prepare callback with a new flag
  "need_update" for the clock reference object, just like others.

- The configure_endpoints() are simplified and folded back into
  snd_usb_pcm_prepare().

Fixes: bf6313a0ff ("ALSA: usb-audio: Refactor endpoint management")
Fixes: ff878b408a ("ALSA: usb-audio: Split endpoint setups for hw_params and prepare")
Reported-by: chihhao chen <chihhao.chen@mediatek.com>
Link: https://lore.kernel.org/r/87e6d6ae69d68dc588ac9acc8c0f24d6188375c3.camel@mediatek.com
Link: https://lore.kernel.org/r/20220901124136.4984-1-tiwai@suse.de
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216500
Link: https://lore.kernel.org/r/20220920181106.4894-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
2022-09-20 20:12:34 +02:00
arch Misc irqchip fixes: LoongArch driver fixes and a Hyper-V IOMMU fix. 2022-08-21 15:09:55 -07:00
block block-6.0-2022-08-19 2022-08-20 10:17:05 -07:00
certs Kbuild updates for v5.20 2022-08-10 10:40:41 -07:00
crypto crypto: blake2b: effectively disable frame size warning 2022-08-10 17:59:11 -07:00
Documentation ALSA: doc: Drop snd_dma_continuous_data() usages 2022-08-24 08:00:26 +02:00
drivers Misc irqchip fixes: LoongArch driver fixes and a Hyper-V IOMMU fix. 2022-08-21 15:09:55 -07:00
fs 5 cifs/smb3 fixes, one for stable 2022-08-21 10:21:16 -07:00
include ALSA: hda: ext: fix locking in stream_release 2022-09-20 08:08:14 +02:00
init asm goto: eradicate CC_HAS_ASM_GOTO 2022-08-21 10:06:28 -07:00
io_uring io_uring/net: use right helpers for async_data 2022-08-18 07:27:20 -06:00
ipc Updates to various subsystems which I help look after. lib, ocfs2, 2022-08-07 10:03:24 -07:00
kernel Various fixes for tracing: 2022-08-21 14:49:42 -07:00
lib lib/cpumask: drop always-true preprocessor guard 2022-08-15 11:00:44 -07:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm - hugetlb_vmemmap cleanups from Muchun Song 2022-08-10 11:18:00 -07:00
net tcp: handle pure FIN case correctly 2022-08-18 11:04:56 -07:00
samples Tracing updates for 5.20 / 6.0 2022-08-05 09:41:12 -07:00
scripts asm goto: eradicate CC_HAS_ASM_GOTO 2022-08-21 10:06:28 -07:00
security hardening fixes for v6.0-rc2 2022-08-19 13:56:14 -07:00
sound ALSA: usb-audio: Split endpoint setups for hw_params and prepare (take#2) 2022-09-20 20:12:34 +02:00
tools asm goto: eradicate CC_HAS_ASM_GOTO 2022-08-21 10:06:28 -07:00
usr Not a lot of material this cycle. Many singleton patches against various 2022-05-27 11:22:03 -07:00
virt KVM: Drop unnecessary initialization of "ops" in kvm_ioctl_create_device() 2022-08-19 04:05:43 -04:00
.clang-format PCI/DOE: Add DOE mailbox support functions 2022-07-19 15:38:04 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore kbuild: split the second line of *.mod into *.usyms 2022-05-08 03:16:59 +09:00
.mailmap Updates to various subsystems which I help look after. lib, ocfs2, 2022-08-07 10:03:24 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS drm for 5.20/6.0 2022-08-03 19:52:08 -07:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS 5 cifs/smb3 fixes, one for stable 2022-08-21 10:21:16 -07:00
Makefile Linux 6.0-rc2 2022-08-21 17:32:54 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.