AM335x OMAP2 common clock external fixed-clock registration

[mturquette@linaro.org (Mike Turquette)]

On Wed, Apr 15, 2015 at 12:47 PM, Michael Welling <mwelling@ieee.org> wrote:
> On Wed, Apr 15, 2015 at 09:43:30PM +0300, Tero Kristo wrote:
>> On 04/15/2015 05:09 PM, Michael Welling wrote:
>> >On Wed, Apr 15, 2015 at 09:34:48AM +0300, Tero Kristo wrote:
>> >>On 04/15/2015 12:17 AM, Michael Welling wrote:
>> >>>Greetings,
>> >>>
>> >>>I have developed an AM3354 based SoM and it uses an external SI5351 clock
>> >>>generator to drive the clock inputs for an external duart and I2S audio
>> >>>master clock. With the registration according to the documentation the
>> >>>reference clock is not being detected and hence the clock generator is
>> >>>not working as expect.
>> >>>
>> >>>After trying many different things, I started to look around the mailing
>> >>>lists to find information related to this issue.
>> >>>
>> >>>I came acrossed post that has the exact same issue:
>> >>>https://lkml.org/lkml/2013/2/18/468
>> >>>
>> >>>Seeing as the patch did not land upstream, I am wondering if there is
>> >>>a solution that I am not seeing.
>> >>>
>> >>>I am willing to provide a patch given appropriate guidance.
>> >>
>> >>Hi Michael,
>> >>
>> >>The info on the email you referenced is kind of obsolete, TI SoCs
>> >>are calling of_clk_init() during boot now, and thus external clock
>> >>nodes should be registered fine also. Maybe you can provide the
>> >>actual DTS patch you are trying out so we can help better...? Are
>> >
>> >See attached patch and console output.
>>
>> I see a bug in your dt data.
>>
>> <snip>
>>
>> +     clocks {
>> +             ref27: ref27 {
>> +                     #clock-cells = <0>;
>> +                     compatibale = "fixed-clock";
>>
>> This should be compatible, right? DT is annoying in that it doesn't
>> verify property names.
>>
>
> Ooops.
>
> Now the clock appears in /sys/kernel/debug/clk:
> root at som3517-som200:/sys/kernel/debug/clk# cat clk_summary
>    clock                         enable_cnt  prepare_cnt        rate   accuracy   phase
> ----------------------------------------------------------------------------------------
>  ref27                                    0            0    27000000          0 0
> ...
>
> There is still an issue with the si5351.
>
> I had to comment out the clk_put here for the frequency to show up:
> http://lxr.free-electrons.com/source/drivers/clk/clk-si5351.c#L1133
>
> Ideas?

What is the most recent upstream commit that you are based on?

Regards,
Mike

>
>> +                     clock-frequency = <27000000>;
>> +             };
>> +     };
>>
>> -Tero
>>
>> >
>> >>you seeing any boot time error / warning prints for your new clock?
>> >
>> >With the debug messages on you see that the reference clock is not being
>> >detected.
>> >
>> >Whilest debugging I found that the of_clk_get is returning an error no matter
>> >which clock I pass it:
>> >http://lxr.free-electrons.com/source/drivers/clk/clk-si5351.c#L1131
>> >
>> >>
>> >>-Tero
>>