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

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Message-ID: <87ila8tgyn.wl-tiwai@suse.de>
Date:   Tue, 25 Jul 2023 12:37:20 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
Cc:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        alsa-devel@...a-project.org, 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

On Tue, 25 Jul 2023 12:29:07 +0200,
Maarten Lankhorst wrote:
> 
> 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.

Yes, HDA-Intel requires either a workqueue or async firmware-loader
callback because there is some codec module-autoload mechanism that
may happen during the probe phase.  It's not only on AMD, but it's
required in general for all codecs.


Takashi