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

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Date:   Thu, 2 May 2019 07:20:16 -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, 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 <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?

Regards,

Tony

> Signed-off-by: Faiz Abbas <faiz_abbas@...com>
> ---
>  arch/arm/boot/dts/am57xx-idk-common.dtsi | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm/boot/dts/am57xx-idk-common.dtsi b/arch/arm/boot/dts/am57xx-idk-common.dtsi
> index f7bd26458915..42e433da79ec 100644
> --- a/arch/arm/boot/dts/am57xx-idk-common.dtsi
> +++ b/arch/arm/boot/dts/am57xx-idk-common.dtsi
> @@ -420,6 +420,7 @@
>  	vqmmc-supply = <&ldo1_reg>;
>  	bus-width = <4>;
>  	cd-gpios = <&gpio6 27 GPIO_ACTIVE_LOW>; /* gpio 219 */
> +	no-1-8-v;
>  };
>  
>  &mmc2 {
> -- 
> 2.19.2
>