linux-kernel - Re: [PATCH v3] ASoC: da7219: read fmw property to get mclk for non-dts systems

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Date:   Mon, 7 May 2018 10:20:10 +0530
From:   "Agrawal, Akshu" <Akshu.Agrawal@....com>
To:     Adam Thomson <Adam.Thomson.Opensource@...semi.com>
Cc:     "djkurtz@...omium.org" <djkurtz@...omium.org>,
        "Alexander.Deucher@....com" <Alexander.Deucher@....com>,
        Support Opensource <Support.Opensource@...semi.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        "moderated list:SOUND" <alsa-devel@...a-project.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] ASoC: da7219: read fmw property to get mclk for
 non-dts systems



On 5/4/2018 2:45 PM, Adam Thomson wrote:
> On 03 May 2018 08:59, Akshu Agrawal wrote:
> 
>> Non-dts based systems can use ACPI DSDT to pass on the mclk
>> to da7219.
>> This enables da7219 mclk to be linked to system clock.
>> Enable/Disable of the mclk is already handled in the codec so
>> platform drivers don't have to explicitly do handling of mclk.
>>
>> Signed-off-by: Akshu Agrawal <akshu.agrawal@....com>
>> ---
>> v2: Fixed kbuild error
>> v3: Add corresponding clk_put for clk_get
>>  include/sound/da7219.h    |  2 ++
>>  sound/soc/codecs/da7219.c | 10 +++++++++-
>>  2 files changed, 11 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/sound/da7219.h b/include/sound/da7219.h
>> index 1bfcb16..df7ddf4 100644
>> --- a/include/sound/da7219.h
>> +++ b/include/sound/da7219.h
>> @@ -38,6 +38,8 @@ struct da7219_pdata {
>>
>>  	const char *dai_clks_name;
>>
>> +	const char *mclk_name;
>> +
>>  	/* Mic */
>>  	enum da7219_micbias_voltage micbias_lvl;
>>  	enum da7219_mic_amp_in_sel mic_amp_in_sel;
>> diff --git a/sound/soc/codecs/da7219.c b/sound/soc/codecs/da7219.c
>> index 980a6a8..ecd46fc 100644
>> --- a/sound/soc/codecs/da7219.c
>> +++ b/sound/soc/codecs/da7219.c
>> @@ -1624,6 +1624,8 @@ static struct da7219_pdata *da7219_fw_to_pdata(struct
>> snd_soc_component *compone
>>  		dev_warn(dev, "Using default clk name: %s\n",
>>  			 pdata->dai_clks_name);
>>
>> +	device_property_read_string(dev, "dlg,mclk-name", &pdata->mclk_name);
>> +
> 
> Personally am still not keen on this. To me the use of a device_property_*
> function suggests the same property resides in both DT and ACPI, but here we're
> only using this for the ACPI case. DT has no want or need for this. I still feel
> we should look at something more generic in the clock framework, although I do
> agree with Mark that this should be properly specced.
> 

I am not an expert in field of ACPI, IMO forming a Spec and changing
ACPI to have DT like clock framework is good to have but a bigger change
which should be taken up later.

The current code of handling of mclk in the driver is usable only by DT.
The device_property (though ACPI specific) makes this code, a common
code for DT and ACPI based devices.

https://www.kernel.org/doc/Documentation/acpi/DSD-properties-rules.txt
"....Still, for the sake of code re-use, it may make sense to provide as
much of the configuration data as possible in the form of device
properties and complement that with an ACPI-specific mechanism suitable
for the use case at hand......"

Thanks,
Akshu