Re: [PATCH] ARM: dts: am57xx-idk: Remove support for voltage switching for SD card

From: Faiz Abbas
Date: Thu May 02 2019 - 10:30:54 EST

Hi Tony,

On 02/05/19 7:50 PM, Tony Lindgren wrote:
> * Faiz Abbas <faiz_abbas@xxxxxx> [190502 01:48]:
>> If UHS speed modes are enabled, a compatible SD card switches down to
>> 1.8V during enumeration. If after this a software reboot/crash takes
>> place and on-chip ROM tries to enumerate the SD card, the difference in
>> IO voltages (host @ 3.3V and card @ 1.8V) may end up damaging the card.
>> The fix for this is to have support for power cycling the card in
>> hardware (with a PORz/soft-reset line causing a power cycle of the
>> card). Since am571x-, am572x- and am574x-idk don't have this
>> capability, disable voltage switching for these boards.
>> The major effect of this is that the maximum supported speed
>> mode is now high speed(50 MHz) down from SDR104(200 MHz).
> This sounds a bit urgent, does it also need a stable tag or is
> it safe to apply against any earlier kernels?

This should be good to apply on any previous releases.