[U-Boot] [PATCH] mmc: Set the initial clock speed to 400KHz

[Jaehoon Chung]

On 05/25/2017 11:02 PM, Phil Edworthy wrote:
> Hi Jaehoon Chung,
> 
> On 25 May 2017 14:50 Jaehoon Chung wrote:
>> Hi,
>>
>> On 05/24/2017 10:54 PM, Phil Edworthy wrote:
>>> The code currently defaults to the slowest clock speed that can be
>>> achieved, which can be significantly lower than the SD spec.
>>
>> Is there any problem..As i know, it should be changed from 1 to min_clk.
> The only problem is that the initial SD clock can be very slow so it increases
> the time to start SD. Admittedly, it's a very small increase in time, but we
> should use the correct initial clock speed.

Well..i didn't agree yet...

If mmc_set_clock(mmc, 400K) and mmc->cfg->f_min is 300K?
Initial clock should be always 400K..but spec is mentioned "initial clock is maximum 400K.."
It means the clock can be the value under 400K.

> 
> Thanks
> Phil
> 
>>>
>>> Signed-off-by: Phil Edworthy <phil.edworthy at renesas.com>
>>> ---
>>>  drivers/mmc/mmc.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c index
>>> 72fc177..dff1be3 100644
>>> --- a/drivers/mmc/mmc.c
>>> +++ b/drivers/mmc/mmc.c
>>> @@ -1676,7 +1676,7 @@ int mmc_start_init(struct mmc *mmc)  #endif
>>>  	mmc->ddr_mode = 0;
>>>  	mmc_set_bus_width(mmc, 1);
>>> -	mmc_set_clock(mmc, 1);
>>> +	mmc_set_clock(mmc, 400000);
>>>
>>>  	/* Reset the Card */
>>>  	err = mmc_go_idle(mmc);
>>>
> 
> 
> 
>