linux-kernel - Re: [PATCH] ARM: dts: am57xx: Disable voltage switching for SD card

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Message-ID: <20190627113904.GI5447@atomide.com>
Date:   Thu, 27 Jun 2019 04:39:04 -0700
From:   Tony Lindgren <tony@...mide.com>
To:     Faiz Abbas <faiz_abbas@...com>
Cc:     linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-omap@...r.kernel.org, mark.rutland@....com,
        robh+dt@...nel.org, robertcnelson@...il.com
Subject: Re: [PATCH] ARM: dts: am57xx: Disable voltage switching for SD card

* Faiz Abbas <faiz_abbas@...com> [190619 03:25]:
> 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). Because the beaglebone X15 (rev A,B and C), am57xx-idks and
> am57xx-evms 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).
> 
> commit 88a748419b84 ("ARM: dts: am57xx-idk: Remove support for voltage
> switching for SD card") did this only for idk boards. Do it for all
> affected boards.

Thanks applying into fixes.

Regards,

Tony