linux-kernel - [PATCH v2 0/5] soundwire: Fixes for spurious and missing UNATTACH

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Date:   Wed, 7 Sep 2022 09:52:54 +0100
From:   Richard Fitzgerald <rf@...nsource.cirrus.com>
To:     <vkoul@...nel.org>, <yung-chuan.liao@...ux.intel.com>,
        <pierre-louis.bossart@...ux.intel.com>, <sanyog.r.kale@...el.com>
CC:     <alsa-devel@...a-project.org>, <linux-kernel@...r.kernel.org>,
        <patches@...nsource.cirrus.com>,
        Richard Fitzgerald <rf@...nsource.cirrus.com>
Subject: [PATCH v2 0/5] soundwire: Fixes for spurious and missing UNATTACH

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.

Tested with 4 peripherals on 1 bus, and 8 peripherals on 2 buses.

CHANGES SINCE V1:
Patch #3 replaced with a better solution to the same bug.
Patches #4 and #5 added to fix some more bugs that were found.

Richard Fitzgerald (4):
  soundwire: bus: Don't lose unattach notifications
  soundwire: bus: Don't re-enumerate before status is UNATTACHED
  soundwire: cadence: Fix lost ATTACHED interrupts when enumerating
  soundwire: bus: Don't exit early if no device IDs were programmed

Simon Trimmer (1):
  soundwire: cadence: fix updating slave status when a bus has multiple
    peripherals

 drivers/soundwire/bus.c            | 40 +++++++++++-----
 drivers/soundwire/cadence_master.c | 75 ++++++++++++++++--------------
 2 files changed, 68 insertions(+), 47 deletions(-)

-- 
2.30.2