linux-kernel - Re: [PATCH v2 8/9] ASoC: SOF: Intel: Remove deferred probe for SOF

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Date:   Tue, 25 Jul 2023 12:29:07 +0200
From:   Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        alsa-devel@...a-project.org
Cc:     sound-open-firmware@...a-project.org, linux-kernel@...r.kernel.org,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Cezary Rojewski <cezary.rojewski@...el.com>,
        Liam Girdwood <liam.r.girdwood@...ux.intel.com>,
        Peter Ujfalusi <peter.ujfalusi@...ux.intel.com>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        Mark Brown <broonie@...nel.org>,
        Daniel Baluta <daniel.baluta@....com>,
        Matthew Auld <matthew.auld@...el.com>
Subject: Re: [PATCH v2 8/9] ASoC: SOF: Intel: Remove deferred probe for SOF

Hey,

On 2023-07-24 13:32, Pierre-Louis Bossart wrote:
> 
> 
> On 7/19/23 18:41, Maarten Lankhorst wrote:
>> This was only used to allow modprobing i915, by converting to the
>> -EPROBE_DEFER mechanism, it can be completely removed, and is in
>> fact counterproductive since -EPROBE_DEFER otherwise won't be
>> handled correctly.
> 
> I personally remember only that the request_module("i915") was the main
> motivation for the use of the workqueue, but when it comes to the
> HDaudio codec management we don't even know what we don't know.
> 
> I am a bit worried that the snd-hda-intel driver keeps the workqueue for
> HDaudio codec initialization, and this patch removes the workqueue
> completely for SOF. That doesn't seem right. Either both drivers need a
> workqueue or none need a workqueue.
> 
> Maybe what we need is to move the i915/xe initialization out of the
> workqueue, and see in a second pass if that workqueue can be safely
> removed from the SOF driver?
> 
As I mentioned in some of the other sound driver conversions. I believe 
it's possible to completely kill off most workqueues.

However, I don´t have the hardware or knowledge to test it. I saw that 
the SOF had the non-workqueue path already, so it felt less risky to 
simply convert it to always use that path.

avs/skylake drivers should be easy to convert too. This is why I left 
the comment: "Removing the workqueue would simplify init even further, 
but is left as exercise for the reviewer."

HDA-intel has this retry-probe logic used on AMD's,
which makes me more hesitant to convert it.

I wanted to tackle one problem at a time, I believe workqueue removal 
can be done by anyone.

Cheers,
~Maarten