[alsa-devel] [PATCH v2 2/2] ARM: dts: Append clock bindings for sai2 on VF610 platform

[Li.Xiubo at freescale.com]

> Subject: Re: [PATCH v2 2/2] ARM: dts: Append clock bindings for sai2 on VF610
> platform
> 
> Hi Shawn,
> 
>    Thanks for the comments, but...
> 
> On Wed, Apr 02, 2014 at 09:03:04PM +0800, Shawn Guo wrote:
> > On Wed, Apr 02, 2014 at 06:10:20PM +0800, Nicolin Chen wrote:
> > > Since we added fours clock to the DT binding, we should update the current
> > > SAI dts/dtsi so as not to break their functions.
> > >
> > > Signed-off-by: Nicolin Chen <Guangyu.Chen at freescale.com>
> > > ---
> > >  arch/arm/boot/dts/vf610.dtsi | 6 ++++--
> > >  1 file changed, 4 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/arch/arm/boot/dts/vf610.dtsi b/arch/arm/boot/dts/vf610.dtsi
> > > index d31ce1b..9fd0007 100644
> > > --- a/arch/arm/boot/dts/vf610.dtsi
> > > +++ b/arch/arm/boot/dts/vf610.dtsi
> > > @@ -139,8 +139,10 @@
> > >  				compatible = "fsl,vf610-sai";
> > >  				reg = <0x40031000 0x1000>;
> > >  				interrupts = <0 86 0x04>;
> > > -				clocks = <&clks VF610_CLK_SAI2>;
> > > -				clock-names = "sai";
> > > +				clocks = <&clks VF610_CLK_SAI2>,
> > > +				       <&clks VF610_CLK_SAI2>,
> > > +				       <&clks 0>, <&clks 0>;
> >
> > So it seems that SAI on vf610 does work with only one clock.  So the
> > driver change will break old DTB for vf610?  If that's case, we will
> > have to need a new compatible for cases where 4 clocks are needed.
> 
> According to Vybrid's RM Chapter 9.11.12 SAI clocking, the SoC actually
> connects SAI with two clocks: SAI_CLK and Platform Bus Clock. So the DT
> binding here still needs to be corrected even if ignoring driver change.
> 
> Besides, I've checked both SAI on imx and vf610 and found that they are
> seemly identical, especially for the clock part -- "The transmitter and
> receiver can independently select between the bus clock and up to three
> audio master clocks to generate the bit clock." And the driver that was
> designed for vf610 already contains the code to switch the clock between
> Bus Clock and Three MCLKs. What I want to say is, even if SAI on vf610
> does work with only one clock, it still doesn't have the full function
> on vf610 -- driving clock from Platform Bus Clock unless we make this
> improvement to the DT binding.
> 
> So I think it's fair to complete the code here for both platforms, even
> though we might take the risk of merging conflict. And I understand
> your point to avoid function break on those platform both of us aren't
> convenient to test. But I've already involved Xiubo in the list. And
> we can wait for his test result.
> 

This has been test on my Vybird-TWR board and it's fine.

Thanks,

Brs
Xiubo



> Hope you can understand the circumstance,
> Nicolin