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

[Michael Walle]

Hi Sameer,

Am 2021-03-09 17:27, schrieb Sameer Pujar:
> On 3/9/2021 8:11 PM, Michael Walle wrote:
> > > If "clocks = <&xxx>" is specified from the CPU or Codec component
> > > device node, the clock is not getting enabled. Thus audio playback
> > > or capture fails.
> > >
> > > Fix this by populating "simple_dai->clk" field when clocks property
> > > is specified from device node as well. Also tidy up by re-organising
> > > conditional statements of parsing logic.
> > >
> > > Fixes: bb6fc620c2ed ("ASoC: simple-card-utils: add 
> > > asoc_simple_card_parse_clk()")
> > > Cc: Kuninori Morimoto <kuninori.morimoto.gx@xxxxxxxxxxx>
> > > Signed-off-by: Sameer Pujar <spujar@xxxxxxxxxx>
> >
> > This actually breaks sound on my board
> > (arch/arm64/boot/dts/freescale/fsl-ls1028a-kontron-sl28-var3-ads2.dts).
> > The codec on this board (wm8904) has a fixed clock input (only 
> > distinct
> > frequencies are supported) and uses the FLL of the codec to generate 
> > the
> > desired sample rate.
> >
> > It seems that after this patch the clock rate of the codecs clock 
> > (rather
> > than the FLL) is tried to be changed. Which fails, because it doesn't
> > support arbitrary frequencies.
>
> Yes, after the given change the clock will be updated if "*mclk-fs"
> property is specified.
>
> DT you mentioned has property "simple-audio-card,mclk-fs = <256>",
> which means you need a clock that is a function of sample rate. But as
> per above you want a fixed clock for MCLK. I think if you drop this
> property, the clock updates won't happen. Earlier for your case, this
> property was not used at all because the clock handle was not
> populated.

You mean to drop the mclk-fs property? I can't do that because I
actually need a frequency of 256 * sample rate. But that doesn't
necessarily need to be the MCLK, because the codec itself has a
FLL/PLL which can be used to generate any frequency for a given
MCLK. So that is a valid scenario. See also commit 13409d27cb39
("ASoC: wm8904: configure sysclk/FLL automatically").

-michael