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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1a14e117-4216-b98d-f972-c9a02cf79d1e@amd.com>
Date:   Thu, 12 Jan 2023 09:29:39 -0600
From:   "Limonciello, Mario" <mario.limonciello@....com>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        "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>,
        arungopal.kondaveeti@....com,
        Syed Saba Kareem <Syed.SabaKareem@....com>
Subject: Re: [PATCH 19/19] ASoC: amd: ps: increase runtime suspend delay

On 1/12/2023 08:54, Pierre-Louis Bossart wrote:
> 
> 
> 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.

Rather than a timing dependency, could you perhaps prohibit runtime PM 
and have a codec make a callback to indicate it's fully initialized and 
then allow runtime PM again?