Re: [PATCH] mmc: core: Fix init of SD cards reporting an invalid VDD range

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On Wed, 28 Aug 2019 at 03:15, Philip Langdale <philipl@xxxxxxxxx> wrote:
>
> On Tue, 27 Aug 2019 10:10:43 +0200
> Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
>
> > The OCR register defines the supported range of VDD voltages for SD
> > cards. However, it has turned out that some SD cards reports an
> > invalid voltage range, for example having bit7 set.
> >
> > When a host supports MMC_CAP2_FULL_PWR_CYCLE and some of the voltages
> > from the invalid VDD range, this triggers the core to run a power
> > cycle of the card to try to initialize it at the lowest common
> > supported voltage. Obviously this fails, since the card can't support
> > it.
> >
> > Let's fix this problem, by clearing invalid bits from the read OCR
> > register for SD cards, before proceeding with the VDD voltage
> > negotiation.
> >
> > Cc: stable@xxxxxxxxxxxxxxx
> > Reported-by: Philip Langdale <philipl@xxxxxxxxx>
> > Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> > ---
> >  drivers/mmc/core/sd.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
> > index d681e8aaca83..fe914ff5f5d6 100644
> > --- a/drivers/mmc/core/sd.c
> > +++ b/drivers/mmc/core/sd.c
> > @@ -1292,6 +1292,12 @@ int mmc_attach_sd(struct mmc_host *host)
> >                       goto err;
> >       }
> >
> > +     /*
> > +      * Some SD cards claims an out of spec VDD voltage range.
> > Let's treat
> > +      * these bits as being in-valid and especially also bit7.
> > +      */
> > +     ocr &= ~0x7FFF;
> > +
> >       rocr = mmc_select_voltage(host, ocr);
> >
> >       /*
>
> Looks right. Tried it out and worked as expected.
>
> Reviewed-by: Philip Langdale <philipl@xxxxxxxxx>

Thanks! I add your tested-by tag as well!

Kind regards
Uffe



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