Re: [PATCH] mmc: change initial clock setting

[Jaehoon Chung <jh80.chung@samsung.com>]

On 2010-06-18 오후 9:42, Matt Fleming wrote:
> On Fri, 18 Jun 2010 13:05:44 +0900, Jaehoon Chung <jh80.chung@samsung.com> wrote:
>> This patch is bug fixed..
>> I think that host->ios.clock(initial clock) will be set lower than 400KHz.
>> But in this code, if host->f_min is higher than 400KHz, print warning message and set higher than 400KHz.
>> And We use SDHCI_QUIRK_NONSTANDARD_CLOCK..so using get_min_clock function. 
>> but didn't effect nothing through used get_min_clock function.
> 
> I'm a little confused. What problem are you fixing with this patch? What
> issue are you seeing? SDHCI_QUIRK_NONSTANDARD_CLOCK is only for sdhci.
> If this is the old "my card won't initialise at 400kHz" chestnut I don't
> think a solution has ever been agreed upon. The problem was that while
> some cards won't initialise at 400kHz, some controllers will try to
> initialise at too low a frequency which causes other problems.
> 
> Sascha Hauer explains the reason for setting ios.clock to 400kHz here,
> 
>        http://lkml.org/lkml/2010/1/5/120
> 
> So I think your patch will cause problems.
> 
> Which driver are you using? The driver should have set the f_min value
> to be <= 400kHz. Maybe it is a good idea to set the value of ios.clock
> to 400kHz if the driver has set a bogus f_min value, we will at least
> have a fighting chance of initialising the card (though I would say that
> the driver was broken, but at least core.c will print a warning).
> 

when ios.clock is higher than 400KHz, why not change 400KHz?(if 400KHz seemed like good value)
if clock value is higher than 400KHz, i think card can't initialize...maybe

when sdhci controller set f_min value(ie, 300KHz), clock changed 400KHz in core.c.
just this code purpose to print warning message?