Re: [RFC PATCH] ASoC: wm8904: add CCF support

Bo Shen
2014-03-25T08:19:40Z

Hi Mark,

On 03/25/2014 04:01 PM, Bo Shen wrote:
> Hi Mark,
>
> On 03/24/2014 07:06 PM, Mark Brown wrote:
>> On Mon, Mar 24, 2014 at 10:15:51AM +0800, Bo Shen wrote:
>>> On 03/21/2014 07:55 PM, Mark Brown wrote:
>>>> On Fri, Mar 21, 2014 at 10:37:47AM +0000, Mark Rutland wrote:
>>>>> On Fri, Mar 21, 2014 at 02:51:02AM +0000, Bo Shen wrote:
>>
>>>>>> + - wlf,sysclk-from-mclk: set the sys clock is driven from mclk,
>>
>>>>> Why can the kernel not decide this?
>>
>>>> It can.
>>
>>> I really don't know how it decided by kernel (hardcode in machine
>>> driver ?),
>>> can you point me directly? Thanks.
>>
>> It can just look to see if there is a suitable system clock present,
>> this shouldn't be hard. If there's a clock connected at a suitable
>> rate it should use that, otherwise if there's a clock at an unsuitable
>> rate it should either change the rate of the clock or use the FLL.
>
> I try to implement this, I think we can write the wm8904 dt as simple as
> following, can it be acceptable?
>
> Case 1: using SoC provided clock
> wm8904:wm8904@1a {
> compatible = "wlf,wm8904";
> reg = <0x1a>;
> clocks = <&pck0>;
> clock-name = "mclk";
> }
>
> Case 2: using external crystal (For this case, I have no idea to put to
> CCF, so need "wlf,xtal-clk-freq" property).
> wm8904:wm8904@1a {
> compatible = "wlf,wm8904";
> reg = <0x1a>;
> wlf,xtal-clk-freq = <12000000>;
> }

Please forget this, with Boris's help, we can use clk-fixed-rate.c driver.

So, I will try to implement another RFC patch.

> Then we use these clocks to configure FLL.
>
> Btw, I see the "wm2000.c" retrieve the clock, however not see the usage
> cases for it.
>
> Best Regards,
> Bo Shen
>
>

Best Regards,
Bo Shen