SoC: simple-card-utils: set 0Hz to sysclk when shutdown
diff mbox series

Message ID 20190907174501.19833-1-katsuhiro@katsuster.net
State Accepted
Commit 2458adb8f92ad4d07ef7ab27c5bafa1d3f4678d6
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Series
  • SoC: simple-card-utils: set 0Hz to sysclk when shutdown
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Commit Message

Katsuhiro Suzuki Sept. 7, 2019, 5:45 p.m. UTC
This patch set 0Hz to sysclk when shutdown the card.

Some codecs set rate constraints that derives from sysclk. This
mechanism works correctly if machine drivers give fixed frequency.

But simple-audio and audio-graph card set variable clock rate if
'mclk-fs' property exists. In this case, rate constraints will go
bad scenario. For example a codec accepts three limited rates
(mclk / 256, mclk / 384, mclk / 512).

Bad scenario as follows (mclk-fs = 256):
   - Initialize sysclk by correct value (Ex. 12.288MHz)
     - Codec set constraints of PCM rate by sysclk
       48kHz (1/256), 32kHz (1/384), 24kHz (1/512)
   - Play 48kHz sound, it's acceptable
   - Sysclk is not changed

   - Play 32kHz sound, it's acceptable
   - Set sysclk to 8.192MHz (= fs * mclk-fs = 32k * 256)
     - Codec set constraints of PCM rate by sysclk
       32kHz (1/256), 21.33kHz (1/384), 16kHz (1/512)

   - Play 48kHz again, but it's NOT acceptable because constraints
     do not allow 48kHz

So codecs treat 0Hz sysclk as signal of applying no constraints to
avoid this problem.

Signed-off-by: Katsuhiro Suzuki <katsuhiro@katsuster.net>
---
 sound/soc/generic/simple-card-utils.c | 7 +++++++
 1 file changed, 7 insertions(+)

Comments

Kuninori Morimoto Sept. 9, 2019, 12:31 a.m. UTC | #1
Hi Katsuhiro

> This patch set 0Hz to sysclk when shutdown the card.
> 
> Some codecs set rate constraints that derives from sysclk. This
> mechanism works correctly if machine drivers give fixed frequency.
> 
> But simple-audio and audio-graph card set variable clock rate if
> 'mclk-fs' property exists. In this case, rate constraints will go
> bad scenario. For example a codec accepts three limited rates
> (mclk / 256, mclk / 384, mclk / 512).
> 
> Bad scenario as follows (mclk-fs = 256):
>    - Initialize sysclk by correct value (Ex. 12.288MHz)
>      - Codec set constraints of PCM rate by sysclk
>        48kHz (1/256), 32kHz (1/384), 24kHz (1/512)
>    - Play 48kHz sound, it's acceptable
>    - Sysclk is not changed
> 
>    - Play 32kHz sound, it's acceptable
>    - Set sysclk to 8.192MHz (= fs * mclk-fs = 32k * 256)
>      - Codec set constraints of PCM rate by sysclk
>        32kHz (1/256), 21.33kHz (1/384), 16kHz (1/512)
> 
>    - Play 48kHz again, but it's NOT acceptable because constraints
>      do not allow 48kHz
> 
> So codecs treat 0Hz sysclk as signal of applying no constraints to
> avoid this problem.
> 
> Signed-off-by: Katsuhiro Suzuki <katsuhiro@katsuster.net>
> ---

I'm not 100% understand your issue.
.hw_params (= set mclk/sysclk) is not called in bad case ??
Or it is called but Codec driver ignores it somehow ??

Thank you for your help !!
Best regards
---
Kuninori Morimoto
Katsuhiro Suzuki Sept. 9, 2019, 2:49 a.m. UTC | #2
On 2019/09/09 9:31, Kuninori Morimoto wrote:
> 
> Hi Katsuhiro
> 
>> This patch set 0Hz to sysclk when shutdown the card.
>>
>> Some codecs set rate constraints that derives from sysclk. This
>> mechanism works correctly if machine drivers give fixed frequency.
>>
>> But simple-audio and audio-graph card set variable clock rate if
>> 'mclk-fs' property exists. In this case, rate constraints will go
>> bad scenario. For example a codec accepts three limited rates
>> (mclk / 256, mclk / 384, mclk / 512).
>>
>> Bad scenario as follows (mclk-fs = 256):
>>     - Initialize sysclk by correct value (Ex. 12.288MHz)
>>       - Codec set constraints of PCM rate by sysclk
>>         48kHz (1/256), 32kHz (1/384), 24kHz (1/512)
>>     - Play 48kHz sound, it's acceptable
>>     - Sysclk is not changed
>>
>>     - Play 32kHz sound, it's acceptable
>>     - Set sysclk to 8.192MHz (= fs * mclk-fs = 32k * 256)
>>       - Codec set constraints of PCM rate by sysclk
>>         32kHz (1/256), 21.33kHz (1/384), 16kHz (1/512)
>>
>>     - Play 48kHz again, but it's NOT acceptable because constraints
>>       do not allow 48kHz
>>
>> So codecs treat 0Hz sysclk as signal of applying no constraints to
>> avoid this problem.
>>
>> Signed-off-by: Katsuhiro Suzuki <katsuhiro@katsuster.net>
>> ---
> 
> I'm not 100% understand your issue.
> .hw_params (= set mclk/sysclk) is not called in bad case ??
> Or it is called but Codec driver ignores it somehow ??
> 

Ah, sorry for confusing. It's not either. hw_params() of machine
driver has been called even if constraints don't have a requested
PCM rate. But it's not expected.

For example, if constraints are 32k, 21.33k, 16k, hw_params() will
be called with 32k when an user requests to play 48k sounds.


> Thank you for your help !!
> Best regards
> ---
> Kuninori Morimoto
> 

Best Regards,
Katsuhiro Suzuki
Kuninori Morimoto Sept. 9, 2019, 3:54 a.m. UTC | #3
Hi Katsuhiro

> >> Bad scenario as follows (mclk-fs = 256):
> >>     - Initialize sysclk by correct value (Ex. 12.288MHz)
> >>       - Codec set constraints of PCM rate by sysclk
> >>         48kHz (1/256), 32kHz (1/384), 24kHz (1/512)
> >>     - Play 48kHz sound, it's acceptable
> >>     - Sysclk is not changed
> >> 
> >>     - Play 32kHz sound, it's acceptable
> >>     - Set sysclk to 8.192MHz (= fs * mclk-fs = 32k * 256)
> >>       - Codec set constraints of PCM rate by sysclk
> >>         32kHz (1/256), 21.33kHz (1/384), 16kHz (1/512)
> >> 
> >>     - Play 48kHz again, but it's NOT acceptable because constraints
> >>       do not allow 48kHz
(snip)
> Ah, sorry for confusing. It's not either. hw_params() of machine
> driver has been called even if constraints don't have a requested
> PCM rate. But it's not expected.
> 
> For example, if constraints are 32k, 21.33k, 16k, hw_params() will
> be called with 32k when an user requests to play 48k sounds.

Oh, I see.
Thank you for explaining.

Thank you for your help !!
Best regards
---
Kuninori Morimoto

Patch
diff mbox series

diff --git a/sound/soc/generic/simple-card-utils.c b/sound/soc/generic/simple-card-utils.c
index 556b1a789629..9b794775df53 100644
--- a/sound/soc/generic/simple-card-utils.c
+++ b/sound/soc/generic/simple-card-utils.c
@@ -213,10 +213,17 @@  EXPORT_SYMBOL_GPL(asoc_simple_startup);
 void asoc_simple_shutdown(struct snd_pcm_substream *substream)
 {
 	struct snd_soc_pcm_runtime *rtd = substream->private_data;
+	struct snd_soc_dai *codec_dai = rtd->codec_dai;
+	struct snd_soc_dai *cpu_dai = rtd->cpu_dai;
 	struct asoc_simple_priv *priv = snd_soc_card_get_drvdata(rtd->card);
 	struct simple_dai_props *dai_props =
 		simple_priv_to_props(priv, rtd->num);
 
+	if (dai_props->mclk_fs) {
+		snd_soc_dai_set_sysclk(codec_dai, 0, 0, SND_SOC_CLOCK_IN);
+		snd_soc_dai_set_sysclk(cpu_dai, 0, 0, SND_SOC_CLOCK_OUT);
+	}
+
 	asoc_simple_clk_disable(dai_props->cpu_dai);
 
 	asoc_simple_clk_disable(dai_props->codec_dai);