Re: [PATCH v2 5/5] ASoC: da7219: properly get clk from the provider

From: Jerome Brunet <jbrunet@baylibre.com>
To: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>,
	Mark Brown <broonie@kernel.org>
Cc: Stephen Boyd <sboyd@kernel.org>,
	alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 5/5] ASoC: da7219: properly get clk from the provider
Date: Mon, 26 Apr 2021 21:35:13 +0200	[thread overview]
Message-ID: <1j7dkon8jy.fsf@starbuckisacylon.baylibre.com> (raw)
In-Reply-To: <69eaa840-ed77-fc01-2925-7e5e9998e80f@linux.intel.com>

On Mon 26 Apr 2021 at 20:10, Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> wrote:

> On 4/21/21 7:05 AM, Jerome Brunet wrote:
>> Instead of using the clk embedded in the clk_hw (which is meant to go
>> away), a clock provider which need to interact with its own clock should
>> request clk reference through the clock provider API.
>> Reviewed-by: Stephen Boyd <sboyd@kernel.org>
>> Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
>
> This patch seems to introduce a regression in our modprobe/rmmod tests

Really sorry about that :/

>
> https://github.com/thesofproject/linux/pull/2870
>
> RMMOD	snd_soc_da7219
> rmmod: ERROR: Module snd_soc_da7219 is in use
>
> Reverting this patch restores the ability to remove the module.
>
> Wondering if devm_ increases a module/device refcount somehow?

The driver is the provider and consumer, so it is consuming itself.
This was the intent, I think the patch should be correct like
this. Maybe I overlooked something on the clock side. I'll check.

I'm not sure the problem is devm_ variant, it might be 
clk_hw_get_clk() simpler variant which also plays with module ref counts.

I don't have this particular HW to check but I'll try to replicate the
test with a dummy module and report ASAP.

Of course, I suppose the same problem applies to PATCH 1 of the series

>
>> ---
>>   sound/soc/codecs/da7219.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>> diff --git a/sound/soc/codecs/da7219.c b/sound/soc/codecs/da7219.c
>> index 13009d08b09a..bd3c523a8617 100644
>> --- a/sound/soc/codecs/da7219.c
>> +++ b/sound/soc/codecs/da7219.c
>> @@ -2181,7 +2181,10 @@ static int da7219_register_dai_clks(struct snd_soc_component *component)
>>   				 ret);
>>   			goto err;
>>   		}
>> -		da7219->dai_clks[i] = dai_clk_hw->clk;
>> +
>> +		da7219->dai_clks[i] = devm_clk_hw_get_clk(dev, dai_clk_hw, NULL);
>> +		if (IS_ERR(da7219->dai_clks[i]))
>> +			return PTR_ERR(da7219->dai_clks[i]);
>>     		/* For DT setup onecell data, otherwise create lookup */
>>   		if (np) {
>> 