Re: [PATCH 1/2] mmc: core: Improve marking broken HPI through devicetree

[Olliver Schinagl]

Hey Jaehoon,

On 19-04-16 11:49, Jaehoon Chung wrote:
> Hi
>
> On 04/19/2016 06:42 PM, Olliver Schinagl wrote:
> > Hi Ulf,
> >
> > On 19-04-16 11:29, Ulf Hansson wrote:
> > > On 19 April 2016 at 09:12, Olliver Schinagl <oliver@xxxxxxxxxxx> wrote:
> > > > In patch 81f8a7be66 Hans de Goede added a patch to allow marking an mmc
> > > > device as to having an broken HPI implementation. After talking some
> > > > with Hans, we now think it is actually the mmc controller that can be
> > > > broken and not support broken HPI's.
> > > I don't want us to invent a DT binding for something you *think* is a
> > > HW controller issue.
> > >
> > > Have you really excluded that this isn't a software issue? Me
> > > personally haven't been using HPI that much so I can't really tell
> > > about the code robustness from the mmc core (mmc protocol point of
> > > view).
> > Well this patch goes hand in hand so to speak with the broken-hpi patch introduced by him, he did most of the investigation. We just discussed how to handle it and asked me to cook up the patch.
> I didn't understand why add this property. Is this same patch?
>
> commit 81f8a7be6642b4c26ab681b2e0f4c4120a6de1b0
> Author: Hans de Goede <hdegoede@xxxxxxxxxx>
> Date:   Wed Apr 1 17:26:23 2015 +0200
>
>      mmc: Add support for marking hpi as broken through devicetree
>
>      The eMMC on a tablet I've will stop working / communicating as soon as
>      the kernel executes:
>
>                  mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
>                                  EXT_CSD_HPI_MGMT, 1,
>                                  card->ext_csd.generic_cmd6_time);
>
>      There seems to be no way to reliable identify eMMC-s which have a broken
>      hpi implementation, but at least for eMMC's which are soldered onto a board
>      we can work around this by specifying that hpi is broken in devicetree.
Similar, this does it on the card level, e.g. you mark a card as having 
a broken HPI implementation.

The truth is, the card may not be broken at all, but the mmc controller 
so we add a property on the controller level.

What Ulf is pondering, if this is not a software stack problem, rather 
then a hardware implementation, which I don't know.
> > @hans, what do you think?
> > > Kind regards
> > > Uffe
> > >
> > > > This patch adds a new capability, mmc-broken-hpi, which allows us to
> > > > mark a broken hpi implementation on the host level.
> > > >
> > > > Signed-off-by: Olliver Schinagl <oliver@xxxxxxxxxxx>
> > > > ---
> > > >    drivers/mmc/core/host.c  | 2 ++
> > > >    drivers/mmc/core/mmc.c   | 2 +-
> > > >    include/linux/mmc/host.h | 1 +
> > > >    3 files changed, 4 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
> > > > index 6e4c55a..9b63b36 100644
> > > > --- a/drivers/mmc/core/host.c
> > > > +++ b/drivers/mmc/core/host.c
> > > > @@ -270,6 +270,8 @@ int mmc_of_parse(struct mmc_host *host)
> > > >                   host->caps |= MMC_CAP_HW_RESET;
> > > >           if (of_property_read_bool(np, "cap-sdio-irq"))
> > > >                   host->caps |= MMC_CAP_SDIO_IRQ;
> > > > +       if (of_property_read_bool(np, "mmc-broken-hpi"))
> > > > +               host->caps |= MMC_CAP_BROKEN_HPI;
> > > >           if (of_property_read_bool(np, "full-pwr-cycle"))
> > > >                   host->caps2 |= MMC_CAP2_FULL_PWR_CYCLE;
> > > >           if (of_property_read_bool(np, "keep-power-in-suspend"))
> > > > diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> > > > index 4dbe3df..9a19562 100644
> > > > --- a/drivers/mmc/core/mmc.c
> > > > +++ b/drivers/mmc/core/mmc.c
> > > > @@ -1592,7 +1592,7 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
> > > >           /*
> > > >            * Enable HPI feature (if supported)
> > > >            */
> > > > -       if (card->ext_csd.hpi) {
> > > > +       if (card->ext_csd.hpi && !(host->caps & MMC_CAP_BROKEN_HPI)) {
> > > >                   err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
> > > >                                   EXT_CSD_HPI_MGMT, 1,
> > > >                                   card->ext_csd.generic_cmd6_time);
> > > > diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> > > > index 8dd4d29..20f758e 100644
> > > > --- a/include/linux/mmc/host.h
> > > > +++ b/include/linux/mmc/host.h
> > > > @@ -264,6 +264,7 @@ struct mmc_host {
> > > >    #define MMC_CAP_DRIVER_TYPE_A  (1 << 23)       /* Host supports Driver Type A */
> > > >    #define MMC_CAP_DRIVER_TYPE_C  (1 << 24)       /* Host supports Driver Type C */
> > > >    #define MMC_CAP_DRIVER_TYPE_D  (1 << 25)       /* Host supports Driver Type D */
> > > > +#define MMC_CAP_BROKEN_HPI     (1 << 29)       /* Host support for HPI is broken */
> > > >    #define MMC_CAP_CMD23          (1 << 30)       /* CMD23 supported. */
> > > >    #define MMC_CAP_HW_RESET       (1 << 31)       /* Hardware reset */
> > > >
> > > > --
> > > > 2.8.0.rc3