linux-kernel - Re: [PATCH v4 0/5] soundwire: Fixes for spurious and missing UNATTACH

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Message-ID: <YylIv9VGYl3VqVIZ@matsya>
Date:   Tue, 20 Sep 2022 10:29:43 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Richard Fitzgerald <rf@...nsource.cirrus.com>
Cc:     yung-chuan.liao@...ux.intel.com,
        pierre-louis.bossart@...ux.intel.com, sanyog.r.kale@...el.com,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        patches@...nsource.cirrus.com
Subject: Re: [PATCH v4 0/5] soundwire: Fixes for spurious and missing UNATTACH

On 14-09-22, 17:02, Richard Fitzgerald wrote:
> The bus and cadence code has several bugs that cause UNATTACH notifications
> to either be sent spuriously or to be missed.
> 
> These can be seen occasionally with a single peripheral on the bus, but are
> much more frequent with multiple peripherals, where several peripherals
> could change state and report in consecutive PINGs.
> 
> The root of all of these bugs seems to be a code design flaw that assumed
> every PING status change would be handled separately. However, PINGs are
> handled by a workqueue function and there is no guarantee when that function
> will be scheduled to run or how much CPU time it will receive. PINGs will
> continue while the work function is handling a snapshot of a previous PING
> so the code must take account that (a) status could change during the
> work function and (b) there can be a backlog of changes before the IRQ work
> function runs again.

Applied, thanks

-- 
~Vinod