linux-kernel - Re: [alsa-devel] [RFC PATCH 2/2] ASoC: samsung: Print a one-time message if the snow driver's probe defers

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Date:   Thu, 20 Oct 2016 08:37:29 -0300
From:   Javier Martinez Canillas <javier@....samsung.com>
To:     Sylwester Nawrocki <s.nawrocki@...sung.com>
Cc:     linux-kernel@...r.kernel.org, alsa-devel@...a-project.org,
        Sangbeom Kim <sbkim73@...sung.com>,
        Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Mark Brown <broonie@...nel.org>
Subject: Re: [alsa-devel] [RFC PATCH 2/2] ASoC: samsung: Print a one-time
 message if the snow driver's probe defers

Hello Sylwester,

On 10/20/2016 08:27 AM, Sylwester Nawrocki wrote:
> On 10/20/2016 12:41 PM, Javier Martinez Canillas wrote:
>> I see no relevant changes in exynos_defconfig between v4.7..v4.8 and
>> also no changes in drivers/Makefile that could cause things to be
>> initialized on a different order.
> 
> I remember this
> 
> commit 6eb1c9496b81680f2cd2e0eda06c531317e2e28d
> clk: probe common clock drivers earlier
> 
> going in recently, but it's rather dubious it could cause such trouble.
>

Yes, I'm aware of this change (and in fact it broke MMC in the Peach Pi
Chromebook) but that commit landed in v4.9-rc1, not v4.8.
 
> Anyway, I'd try to add some debug prints to samsung_i2s_probe() to see
> what's the issue with the CPU DAI registration.
>

Sure, I'm busy with other stuff now but I'll dig again this next week.
 
>> But I thought the patches had merits on its own since probe deferral
>> can make a driver probe many times and the error logs were noisy. I
>> wasn't sure though and that's why are marked as RFC.
> 
> In general I wouldn't be disabling those err logs unless proper
> EPROBE_DEFER handling is added on related error paths and we can
> differentiate between probe deferral and real unrecoverable errors
> and can disable logging only for EPROBE_DEFER cases.
>

Yes, the sound core change (patch 1/2) is only for the EPROBE_DEFER path.
 
>>> As far as the error log is concerned, I would just not print anything
>>> in snow_probe() when register_card() returns EPROBE_DEFER.
>>>
>>
>> I believe it may be useful to know that a driver's probe is deferring 
>> due a missing dependency but have no strong opinion and can remove the
>> message.
> 
> I'd rather rely on core code to inform about missing resources when
> registering components.  Otherwise booting unnecessarily takes more
> time when there is more probe deferring logs printed on the console.
>

Fair enough.
 
> 
> --
> Thanks,
> Sylwester
> 

Best regards,
-- 
Javier Martinez Canillas
Open Source Group
Samsung Research America