Re: [EXT] Re: [PATCH v2] mmc: core: add mmc-card hardware reset enable support

From: Richard Leitner
Date: Tue Jun 20 2017 - 06:34:27 EST



On 06/20/2017 11:45 AM, Linus Walleij wrote:
>> IMHO mmc-util is where the patch really stands: the enabling is OTP,
>> the programmer have to use mmc-util only once and the kernel
>> will behave accordingly.
>
> So we should not add it to the device tree.
>
>> Any platform vendor must check that the HW Reset pin is actually
>> Connected BEFORE enabling this feature otherwise the system may be
>> unstable. A DT Binding may be dangerous if this condition is not met
>> as well as the code execution at each MMC init is honestly redundant
>> for an OTP location of the extCSD.
>
> I agree. So the device should be configured during production, or
> a user who know exactly what they are doing may reconfigure it
> using the mmc-utils.
>
> Thus the kernel should just read what the device says and stay with
> that, no DT props or anything.

Ok. Thanks for that clarification to everybody involved!

Should we then add a warning/info message to the kernel if we have a
reset gpio configured in the DT, but the eMMC hasn't this OTP bit set?

Or should we just leave it as it is? (Due to the fact the reset-gpio
could be connected to an external reset chip?)

kind regards,
Richard.L