Re: [RESEND PATCHv2 1/3] arm: socfpga: Set the SDMMC clock phase in system manager

Dinh Nguyen
2013-10-15T13:22:51Z

Hi Arnd,

On 10/15/13 7:50 AM, Arnd Bergmann wrote:
> On Monday 14 October 2013, dinguyen@altera.com wrote:
>> +void socfpga_sysmgr_set_dwmmc_drvsel_smpsel(u32 drvsel, u32 smplsel)
>> +{
>> + u32 hs_timing;
>> +
>> + hs_timing = SYSMGR_SDMMC_CTRL_SET(smplsel, drvsel);
>> + writel(hs_timing, sys_manager_base_addr + SYSMGR_SDMMCGRP_CTRL_OFFSET);
>> +}
>> +EXPORT_SYMBOL(socfpga_sysmgr_set_dwmmc_drvsel_smpsel);
> This looks like the wrong approach. What are you trying to do? If you want to
> set a clock, please use the clk API.
I can't use the clk API because this function is setting up a clock
phase bit for the SD/MMC
clock that is used to clock the card, not the IP. This register is
located outside the SD/MMC
and the clock manager.

Just to refresh your memory on this topic:
I tried to use the syscon approach that you suggested:

http://lists.infradead.org/pipermail/linux-arm-kernel/2013-May/168470.html
http://lists.infradead.org/pipermail/linux-arm-kernel/2013-May/170423.html

But this approach was rejected by Stephen Warren because we wanted to
the SD driver to be automonous
of registers outside its IP:

http://lists.infradead.org/pipermail/linux-arm-kernel/2013-August/194014.html

So I went with the approach of exposing a platform API so that the
SD/MMC platform specific
code can call it.

The system manager has a plethora of registers that controls other IPs
on the SOC, so I kinda thought
syscon was the way to go with this. A driver for this IP did not make
sense to me.

Please advise if you know of another approach?

Thanks,
Dinh

>
> Arnd