Re: [PATCH 1/3] ASoC: simple-card-utils: Fix device module clock

From: Sameer Pujar <spujar@nvidia.com>
To: Michael Walle <michael@walle.cc>
Cc: Mark Brown <broonie@kernel.org>, <alsa-devel@alsa-project.org>,
	<devicetree@vger.kernel.org>, <jonathanh@nvidia.com>,
	<kuninori.morimoto.gx@renesas.com>,
	<linux-kernel@vger.kernel.org>, <linux-tegra@vger.kernel.org>,
	<robh@kernel.org>, <sharadg@nvidia.com>,
	<thierry.reding@gmail.com>
Subject: Re: [PATCH 1/3] ASoC: simple-card-utils: Fix device module clock
Date: Mon, 15 Mar 2021 21:27:54 +0530	[thread overview]
Message-ID: <99d5d684-54a2-9010-890c-632cdde83030@nvidia.com> (raw)
In-Reply-To: <33a5c89d15ca04ad75f9993bd5d22cb9@walle.cc>

On 3/15/2021 9:03 PM, Michael Walle wrote:
> Am 2021-03-15 16:19, schrieb Sameer Pujar:
>> On 3/15/2021 5:35 PM, Michael Walle wrote:
>>> Am 2021-03-12 14:46, schrieb Mark Brown:
>>>> On Fri, Mar 12, 2021 at 01:30:02PM +0100, Michael Walle wrote:
>>>>
>>>>> The card calls set_sysclk(), which eventually ends up in the codec.
>>>>> The codec therefore, could figure out if it needs to configure the
>>>>> clock or if it can use its internal FLL.
>>>>> Is that what you mean?
>>>>
>>>> Yes.
>>>>
>>>>> But the set_sysclk() of the codec isn't even called, because the
>>>>> card itself already tries to call clk_set_rate() on the Codec's
>>>>> MCLK,
>>>>> which returns with an error [0].
>>>>
>>>> OK, so I think we need to push this down a level so that the clock
>>>> setting is implemented by the core/CODEC rather than by simple-card,
>>>> with the helpers being something the CODEC can opt out of.
>>>
>>> Sameer, it looks like the proper fix should be to add the clock
>>> support to your codec.
>>
>> I agree that complicated clock relationships should be handled within
>> the codec itself, however MCLK rate setting depends on "mclk-fs"
>> factor and this property is specified as part of
>> simple-card/audio-graph-card codec subnode. Right now codec, in
>> general, does not have a way to know this. The set_sysclk() callback
>> takes rate argument and not the factor.
>
> Why would you need the factor?

Sorry, you are right. I misread the flow. Fixed rates can use 
"assigned-clocks" binding and runtime updates can depend on "mclk-fs". 
No additional property is required for codec. Something like below 
should help.

>
> diff --git a/sound/soc/codecs/rt5659.c b/sound/soc/codecs/rt5659.c
> index 67f0ab817135..7fd41f51f856 100644
> --- a/sound/soc/codecs/rt5659.c
> +++ b/sound/soc/codecs/rt5659.c
> @@ -3426,12 +3426,18 @@ static int rt5659_set_component_sysclk(struct
> snd_soc_component *component, int
>  {
>         struct rt5659_priv *rt5659 =
> snd_soc_component_get_drvdata(component);
>         unsigned int reg_val = 0;
> +       int ret;
>
>         if (freq == rt5659->sysclk && clk_id == rt5659->sysclk_src)
>                 return 0;
>
>         switch (clk_id) {
>         case RT5659_SCLK_S_MCLK:
> +               ret = clk_set_rate(rt5659->mclk, freq);
> +               if (ret)
> +                       return ret;
>                 reg_val |= RT5659_SCLK_SRC_MCLK;
>                 break;
>         case RT5659_SCLK_S_PLL1: