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

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Message-ID: <883fda5c-0ef5-8b9c-80fa-4348b4368f5c@linux.intel.com>
Date:   Mon, 26 Apr 2021 13:39:34 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Jerome Brunet <jbrunet@...libre.com>,
        Mark Brown <broonie@...nel.org>
Cc:     Stephen Boyd <sboyd@...nel.org>, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/5] ASoC: da7219: properly get clk from the provider


> 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@...nel.org>
>> Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
> 
> This patch seems to introduce a regression in our modprobe/rmmod tests
> 
> 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 following diff fixes the issue for me

There is an explicit try_module_get() in clk_hw_create_clk, so you 
end-up increasing the refcount of your own module.

devm_ doesn't seem like a good idea here, I think we have to release the 
clk and its implicit module reference when the component is freed, no?

I can send a proper fix if there is consensus.


diff --git a/sound/soc/codecs/da7219.c b/sound/soc/codecs/da7219.c
index bd3c523a8617..8696ac749af3 100644
--- a/sound/soc/codecs/da7219.c
+++ b/sound/soc/codecs/da7219.c
@@ -2182,7 +2182,7 @@ static int da7219_register_dai_clks(struct 
snd_soc_component *component)
                         goto err;
                 }

-               da7219->dai_clks[i] = devm_clk_hw_get_clk(dev, 
dai_clk_hw, NULL);
+               da7219->dai_clks[i] = clk_hw_get_clk(dai_clk_hw, NULL);
                 if (IS_ERR(da7219->dai_clks[i]))
                         return PTR_ERR(da7219->dai_clks[i]);

@@ -2218,6 +2218,8 @@ static int da7219_register_dai_clks(struct 
snd_soc_component *component)
                 if (da7219->dai_clks_lookup[i])
                         clkdev_drop(da7219->dai_clks_lookup[i]);

+               clk_put(da7219->dai_clks[i]);
+
                 clk_hw_unregister(&da7219->dai_clks_hw[i]);
         } while (i-- > 0);

@@ -2240,6 +2242,8 @@ static void da7219_free_dai_clks(struct 
snd_soc_component *component)
                 if (da7219->dai_clks_lookup[i])
                         clkdev_drop(da7219->dai_clks_lookup[i]);

+               clk_put(da7219->dai_clks[i]);
+
                 clk_hw_unregister(&da7219->dai_clks_hw[i]);
         }