[alsa-devel] [PATCH 2/3] ASoC: fsl_asrc: update supported sample format

[S.j. Wang]

Hi

> 
> On Fri, Sep 13, 2019 at 05:48:40AM +0000, S.j. Wang wrote:
> > Hi
> >
> > >
> > > On Tue, Sep 10, 2019 at 02:07:25AM +0000, S.j. Wang wrote:
> > > > > On Mon, Sep 09, 2019 at 06:33:20PM -0400, Shengjiu Wang wrote:
> > > > > > The ASRC support 24bit/16bit/8bit input width, so S20_3LE
> > > > > > format should not be supported, it is word width is 20bit.
> > > > >
> > > > > I thought 3LE used 24-bit physical width. And the driver assigns
> > > > > ASRC_WIDTH_24_BIT to "width" for all non-16bit cases, so 20-bit
> > > > > would go for that 24-bit slot also. I don't clearly recall if I
> > > > > had explicitly tested S20_3LE, but I feel it should work since I put
> there...
> > > >
> > > > For S20_3LE, the width is 20bit,  but the ASRC only support 24bit,
> > > > if set the ASRMCR1n.IWD= 24bit, because the actual width is 20
> > > > bit, the volume is Lower than expected,  it likes 24bit data right shift 4
> bit.
> > > > So it is not supported.
> > >
> > > Hmm..S20_3LE right-aligns 20 bits in a 24-bit slot? I thought
> > > they're left aligned...
> > >
> > > If this is the case...shouldn't we have the same lower-volume
> > > problem for all hardwares that support S20_3LE now?
> >
> > Actually some hardware/module when they do transmission from FIFO to
> > shift register, they can select the start bit, for example from the
> > 20th bit. but not all module have this capability.
> >
> > For ASRC, it haven't.  IWD can only cover the data width,  there is no
> > Other bit for slot width.
> 
> Okay..let's drop the S20_3LE then. But would it be possible for you to
> elaborate the reasoning into the commit message also? Just for case when
> people ask why we remove it simply.
> 
> Thanks

OK.
Best regards
Wang shengjiu