On Mon, 22 Oct 2018 14:23:04 +0200 Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote: > On 18 October 2018 at 17:29, Marek Behún <marek.behun@xxxxxx> wrote: > > Add documentation for no-uhs-voltage MMC property. > > > > Signed-off-by: Marek Behún <marek.behun@xxxxxx> > > Cc: Rob Herring <robh+dt@xxxxxxxxxx> > > Cc: devicetree@xxxxxxxxxxxxxxx > > --- > > Documentation/devicetree/bindings/mmc/mmc.txt | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/Documentation/devicetree/bindings/mmc/mmc.txt > > b/Documentation/devicetree/bindings/mmc/mmc.txt index > > f5a0923b34ca..0506dcbc2070 100644 --- > > a/Documentation/devicetree/bindings/mmc/mmc.txt +++ > > b/Documentation/devicetree/bindings/mmc/mmc.txt @@ -55,6 +55,7 @@ > > Optional properties: > > - no-sdio: controller is limited to send sdio cmd during > > initialization > > - no-sd: controller is limited to send sd cmd during initialization > > - no-mmc: controller is limited to send mmc cmd during > > initialization +- no-uhs-voltage: controller does not support > > switching to UHS voltage > > We already have bindings for telling which UHS modes that are > supported. > > It doesn't make sense to me, to also have a binding saying that UHS > mode isn't supported, as that information is already available. > Hi Ulf, the problem here is that I some boards have hardware bugs which report UHS support but the voltage switch won't work. In this case how should I tell the kernel not to do the voltage_switch? If I looked at the code correctly, currently there isn't a way to specify this via device tree. sd.c function mmc_sd_get_cid calls mmc_set_uhs_voltage if the device reports it (CCS and S18A in the response is set). But mmc_set_uhs_voltage fails on such boards and kernel won't boot root partition. Marek
