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Message-ID: <20190502143525.GP8007@atomide.com>
Date: Thu, 2 May 2019 07:35:25 -0700
From: Tony Lindgren <tony@...mide.com>
To: Faiz Abbas <a0230074@...com>
Cc: Faiz Abbas <faiz_abbas@...com>, 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
* Faiz Abbas <a0230074@...com> [190502 14:30]:
> 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.
OK applying both your MMC patches into fixes today.
Thanks,
Tony
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