Messages in this thread | | | Subject | Re: [PATCH] SoC: simple-card-utils: set 0Hz to sysclk when shutdown | From | Katsuhiro Suzuki <> | Date | Mon, 9 Sep 2019 11:49:27 +0900 |
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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
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