Re: [PATCHv6 2/5] clk: socfpga: Add a clock type for the SD/MMC driver

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 12/16/2013 09:55 PM, Emilio López wrote:
> Hi Mike et al,
>
> El 15/12/13 01:51, Mike Turquette escribió:
>> clk_set_phase has been proposed before and now may be the time to add
>> it. There are two things that need to be addressed:
>>
>> 1) what are the values for the phase? This needs to work for others that
>> must set clk phase, so we need to consider all those requirements before
>> making a new function declaration in clk.h
>>
>> 2) is setting a clock's phase something done dynamically? Put another
>> way, does the same clock has it's phase set multiple times while the
>> system is running? For static configuration that only happens during
>> initialization we do not need a new API. The clock driver can handle it
>> privately. For dynamic operations though we likely need a new API.
>
> We on sunxi also need this for our (not yet merged) MMC driver; we currently have it implemented as an exported
>
> void clk_sunxi_mmc_phase_control(struct clk_hw *hw, u8 sample, u8 output)
>
> that takes the MMC clock (and only the MMC clock) and does the setup (it's basically configuring two values, "sample" and "output", into the clock register). I really don't know what does this do/why is it required/when is it used; I'm cc'ing Hans and David who can hopefully explain that part.

I'm afraid I cannot explain that part, the MMC controller in the sunxi SoCs
is undocumented, so what we're doing there comes straight from the android
kernel code. I do understand most of the bits of the sunxi-mci driver, but
this bit is black magic to me.

Regards,

Hans