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

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Message-ID: <50559611-a501-4331-c88b-5d05f6e756e9@ti.com>
Date:   Thu, 2 May 2019 20:00:14 +0530
From:   Faiz Abbas <a0230074@...com>
To:     Tony Lindgren <tony@...mide.com>, 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>, <bcousson@...libre.com>,
        <ulf.hansson@...aro.org>, <adrian.hunter@...el.com>
Subject: Re: [PATCH] ARM: dts: am57xx-idk: Remove support for voltage
 switching for SD card

Hi Tony,

On 02/05/19 7:50 PM, Tony Lindgren wrote:
> * Faiz Abbas <faiz_abbas@...com> [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.

Thanks,
Faiz