linux-kernel - Re: [PATCH v2 0/9] sound: Use -EPROBE_DEFER instead of i915 module loading.

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Date:   Mon, 31 Jul 2023 18:37:36 +0200
From:   Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     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>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.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>
Subject: Re: [PATCH v2 0/9] sound: Use -EPROBE_DEFER instead of i915 module
 loading.

Hey,

Den 2023-07-31 kl. 17:51, skrev Takashi Iwai:
> On Wed, 19 Jul 2023 18:41:32 +0200,
> Maarten Lankhorst wrote:
>> Explicitly loading i915 becomes a problem when upstreaming the new intel driver
>> for Tiger Lake and higher graphics (xe). By loading i915, it doesn't wait for
>> driver load of xe, and will fail completely before it loads.
>>
>> -EPROBE_DEFER has to be returned before any device is created in probe(),
>> otherwise the removal of the device will cause EPROBE_DEFER to try again
>> in an infinite loop.
>>
>> The conversion is done in gradual steps. First I add an argument to
>> snd_hdac_i915_init to allow for -EPROBE_DEFER so I can convert each driver
>> separately. Then I convert each driver to move snd_hdac_i915_init out of the
>> workqueue. Finally I drop the ability to choose modprobe behavior after the
>> last user is converted.
>>
>> I suspect the avs and skylake drivers used snd_hdac_i915_init purely for the
>> modprobe, but I don't have the hardware to test if it can be safely removed.
>> It can still be done easily in a followup patch to simplify probing.
>>
>> ---
>> New since first version:
>>
>> - snd_hda_core.gpu_bind is added as a mechanism to force gpu binding,
>>    for testing. snd_hda_core.gpu_bind=0 forces waiting for GPU bind to
>>    off, snd_hda_core.gpu_bind=1 forces waiting for gpu bind. Default
>>    setting depends on whether kernel booted with nomodeset.
>> - Incorporated all feedback review.
> Maarten, are you working on v3 patch set?
> Or, for moving forward, should we merge v2 now and fix the rest based
> on that later?

I've been working on a small change to keep the workqueue in SOF and 
only move the binding to the probe function to match what snd-hda-intel 
is doing, but I don't know if that is needed?

It was a bit unclear to me based on feedback if I should try to kill the 
workqueue on all drivers (but with no way to test), or keep it around.

Cheers,

~Maarten