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Message-ID: <ec653abc-f2f8-8a9d-4b8a-ea9d985d32fe@linux.intel.com>
Date:   Mon, 31 Jul 2023 18:37:36 +0200
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Subject: Re: [PATCH v2 0/9] sound: Use -EPROBE_DEFER instead of i915 module
 loading.
To:     Takashi Iwai <tiwai@suse.de>
Cc:     alsa-devel@alsa-project.org, sound-open-firmware@alsa-project.org,
        linux-kernel@vger.kernel.org, Jaroslav Kysela <perex@perex.cz>,
        Takashi Iwai <tiwai@suse.com>,
        Cezary Rojewski <cezary.rojewski@intel.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>,
        Liam Girdwood <liam.r.girdwood@linux.intel.com>,
        Peter Ujfalusi <peter.ujfalusi@linux.intel.com>,
        Bard Liao <yung-chuan.liao@linux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@linux.intel.com>,
        Kai Vehmanen <kai.vehmanen@linux.intel.com>,
        Mark Brown <broonie@kernel.org>,
        Daniel Baluta <daniel.baluta@nxp.com>
References: <20230719164141.228073-1-maarten.lankhorst@linux.intel.com>
 <87r0oohyea.wl-tiwai@suse.de>
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From:   Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
In-Reply-To: <87r0oohyea.wl-tiwai@suse.de>
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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