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

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Date:   Wed, 16 May 2018 09:37:46 +0000
From:   Adam Thomson <Adam.Thomson.Opensource@...semi.com>
To:     "Agrawal, Akshu" <Akshu.Agrawal@....com>,
        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 07 May 2018 05:50, Agrawal, Akshu wrote:

Apologies for the delay in response. Please see comments below.

> 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.

That's fair enough, but I wonder who will take that on. Really would be
beneficial to have something generic on the ACPI side.
 
> 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......"

Given that on the DT side there's the expectation that the generic 'clock-names'
property might be provided to the driver, could we not reuse that rather than
introducing 'dlg,mclk-name' and diverging DT and ACPI properties?

> 
> Thanks,
> Akshu