linux-kernel - Re: [PATCH 19/19] ASoC: amd: ps: increase runtime suspend delay

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Message-ID: <5a34e6f7-eaf1-8128-81e4-81f65541d9a8@linux.intel.com>
Date:   Thu, 12 Jan 2023 08:54:36 -0600
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     "Mukunda,Vijendar" <vijendar.mukunda@....com>, broonie@...nel.org,
        vkoul@...nel.org, alsa-devel@...a-project.org
Cc:     Mastan.Katragadda@....com, Sunil-kumar.Dommati@....com,
        open list <linux-kernel@...r.kernel.org>,
        Basavaraj.Hiregoudar@....com, Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>, Mario.Limonciello@....com,
        arungopal.kondaveeti@....com,
        Syed Saba Kareem <Syed.SabaKareem@....com>
Subject: Re: [PATCH 19/19] ASoC: amd: ps: increase runtime suspend delay



On 1/12/23 05:02, Mukunda,Vijendar wrote:
> On 11/01/23 21:32, Pierre-Louis Bossart wrote:
>> On 1/11/23 03:02, Vijendar Mukunda wrote:
>>> To avoid ACP entering into D3 state during slave enumeration and
>>> initialization on two soundwire controller instances for multiple codecs,
>>> increase the runtime suspend delay to 3 seconds.
>> You have a parent PCI device and a set of child devices for each
>> manager. The parent PCI device cannot suspend before all its children
>> are also suspended, so shouldn't the delay be modified at the manager level?
>>
>> Not getting what this delay is and how this would deal with a lengthy
>> enumeration/initialization process.
> Yes agreed. Until Child devices are suspended, parent device will
> be in D0 state. We will rephrase the commit message.
> 
> Machine driver node will be created by ACP PCI driver.
> We have added delay in machine driver to make sure
> two manager instances completes codec enumeration and
> peripheral initialization before registering the sound card.
> Without adding delay in machine driver will result early card
> registration before codec initialization is completed. Manager
> will enter in to bad state due to codec read/write failures.
> We are intended to keep the ACP in D0 state, till sound card
> is created and jack controls are initialized. To handle, at manager
> level increased runtime suspend delay.

This doesn't look too good. You should not assume any timing
dependencies in the machine driver probe. I made that mistake in earlier
versions and we had to revisit all this to make sure drivers could be
bound/unbound at any time.