Re: [PATCH 1/2] mmc: dw_mmc-exynos: add support for controlling emmc reset pin

[Tobias Jakobi <liquid.acid-hi6Y0CQ0nG0@public.gmane.org>]

Ulf Hansson wrote:
> On 28 January 2015 at 13:41, Tobias Jakobi <liquid.acid-hi6Y0CQ0nG0@public.gmane.org> wrote:
>> Hello!
>>
>> Jaehoon Chung wrote:
>>> mmc core supported to hw_reset function.
>>> So i think we can use it. It's called at only initial time to clear the previous status.
>>> But i think it can be called at reboot time. (it needs to implement codes.)
>>> how about?
>> I don't think that's going the work. The problem here is that depending
>> on the board configuration, the eMMC might carry the bootloader. If the
>> eMMC subsystem is not properly reset _during_ reboot, the board won't
>> even start since no bootloader is found. So we don't even reach the
>> point where the kernel does anything.
> 
> I guess it depends on what's being done during the reboot sequence.
> 
> The most proper thing would be to let the boot loader control the GPIO
> to trigger the HW reset, but that would mean the boot loader need to
> know about board specific configurations, such as which GPIO pin. So
> maybe SOC vendors need to state what GPIO pin to use and don't leave
> that as a configurable option.
Not the bootloader, but the iROM code would have to do this, and as far
as I know the iROM can't be modified. Or am I missing something here?


With best wishes,
Tobias

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