Re: [PATCH V12 10/23] mmc: sdhci-uhs2: add reset function and uhs2_mode function

[Ulf Hansson]

On Tue, 10 Oct 2023 at 12:29, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
>
> On 4/10/23 11:35, Ulf Hansson wrote:
> > On Tue, 3 Oct 2023 at 17:03, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
> >>
> >> On 3/10/23 15:22, Ulf Hansson wrote:
> >>> On Tue, 3 Oct 2023 at 13:37, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
> >>>>
> >>>> On 3/10/23 13:30, Ulf Hansson wrote:
> >>>>> On Fri, 15 Sept 2023 at 11:44, Victor Shih <victorshihgli@xxxxxxxxx> wrote:
> >>>>>>
> >>>>>> From: Victor Shih <victor.shih@xxxxxxxxxxxxxxxxxxx>
> >>>>>>
> >>>>>> Sdhci_uhs2_reset() does a UHS-II specific reset operation.
> >>>>>>
> >>>>>> Signed-off-by: Ben Chuang <ben.chuang@xxxxxxxxxxxxxxxxxxx>
> >>>>>> Signed-off-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
> >>>>>> Signed-off-by: Victor Shih <victor.shih@xxxxxxxxxxxxxxxxxxx>
> >>>>>> Acked-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> >>>>>> ---
> >>>>>>
> >>>>>> Updates in V8:
> >>>>>>  - Adjust the position of matching brackets.
> >>>>>>
> >>>>>> Updates in V6:
> >>>>>>  - Remove unnecessary functions and simplify code.
> >>>>>>
> >>>>>> ---
> >>>>>>
> >>>>>>  drivers/mmc/host/sdhci-uhs2.c | 45 +++++++++++++++++++++++++++++++++++
> >>>>>>  drivers/mmc/host/sdhci-uhs2.h |  2 ++
> >>>>>>  2 files changed, 47 insertions(+)
> >>>>>>
> >>>>>> diff --git a/drivers/mmc/host/sdhci-uhs2.c b/drivers/mmc/host/sdhci-uhs2.c
> >>>>>> index e339821d3504..dfc80a7f1bad 100644
> >>>>>> --- a/drivers/mmc/host/sdhci-uhs2.c
> >>>>>> +++ b/drivers/mmc/host/sdhci-uhs2.c
> >>>>>> @@ -10,7 +10,9 @@
> >>>>>>   *  Author: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
> >>>>>>   */
> >>>>>>
> >>>>>> +#include <linux/delay.h>
> >>>>>>  #include <linux/module.h>
> >>>>>> +#include <linux/iopoll.h>
> >>>>>>
> >>>>>>  #include "sdhci.h"
> >>>>>>  #include "sdhci-uhs2.h"
> >>>>>> @@ -49,6 +51,49 @@ void sdhci_uhs2_dump_regs(struct sdhci_host *host)
> >>>>>>  }
> >>>>>>  EXPORT_SYMBOL_GPL(sdhci_uhs2_dump_regs);
> >>>>>>
> >>>>>> +/*****************************************************************************\
> >>>>>> + *                                                                           *
> >>>>>> + * Low level functions                                                       *
> >>>>>> + *                                                                           *
> >>>>>> +\*****************************************************************************/
> >>>>>> +
> >>>>>> +bool sdhci_uhs2_mode(struct sdhci_host *host)
> >>>>>> +{
> >>>>>> +       return host->mmc->flags & MMC_UHS2_SUPPORT;
> >>>>>
> >>>>> The MMC_UHS2_SUPPORT bit looks redundant to me. Instead, I think we
> >>>>> should be using mmc->ios.timings, which already indicates whether we
> >>>>> are using UHS2 (MMC_TIMING_UHS2_SPEED_*). See patch2 where we added
> >>>>> this.
> >>>>>
> >>>>> That said, I think we should drop the sdhci_uhs2_mode() function
> >>>>> altogether and instead use mmc_card_uhs2(), which means we should move
> >>>>> it to include/linux/mmc/host.h, so it becomes available for host
> >>>>> drivers.
> >>>>>
> >>>>
> >>>> UHS2 mode starts at UHS2 initialization and ends either when UHS2
> >>>> initialization fails, or the card is removed.
> >>>>
> >>>> So it includes re-initialization and reset when the transfer mode
> >>>> currently transitions through MMC_TIMING_LEGACY.
> >>>>
> >>>> So mmc_card_uhs2() won't work correctly for the host callbacks
> >>>> unless something is done about that.
> >>>
> >>> Right, thanks for clarifying!
> >>>
> >>> In that case I wonder if we couldn't change the way we update the
> >>> ->ios.timing for UHS2. It seems silly to have two (similar) ways to
> >>> indicate that we have moved to UHS2.
> >>
> >> Perhaps something like below:
> >>
> >> diff --git a/drivers/mmc/core/sd_uhs2.c b/drivers/mmc/core/sd_uhs2.c
> >> index aacefdd6bc9e..e39d63d46041 100644
> >> --- a/drivers/mmc/core/sd_uhs2.c
> >> +++ b/drivers/mmc/core/sd_uhs2.c
> >> @@ -70,7 +70,8 @@ static int sd_uhs2_power_off(struct mmc_host *host)
> >>
> >>         host->ios.vdd = 0;
> >>         host->ios.clock = 0;
> >> -       host->ios.timing = MMC_TIMING_LEGACY;
> >> +       /* Must set UHS2 timing to identify UHS2 mode */
> >> +       host->ios.timing = MMC_TIMING_UHS2_SPEED_A;
> >>         host->ios.power_mode = MMC_POWER_OFF;
> >>         if (host->flags & MMC_UHS2_SD_TRAN)
> >>                 host->flags &= ~MMC_UHS2_SD_TRAN;
> >> @@ -1095,7 +1096,8 @@ static void sd_uhs2_detect(struct mmc_host *host)
> >>                 mmc_claim_host(host);
> >>                 mmc_detach_bus(host);
> >>                 sd_uhs2_power_off(host);
> >> -               host->flags &= ~MMC_UHS2_SUPPORT;
> >> +               /* Remove UHS2 timing to indicate the end of UHS2 mode */
> >> +               host->ios.timing = MMC_TIMING_LEGACY;
> >>                 mmc_release_host(host);
> >>         }
> >>  }
> >> @@ -1338,7 +1340,8 @@ static int sd_uhs2_attach(struct mmc_host *host)
> >>  err:
> >>         mmc_detach_bus(host);
> >>         sd_uhs2_power_off(host);
> >> -       host->flags &= ~MMC_UHS2_SUPPORT;
> >> +       /* Remove UHS2 timing to indicate the end of UHS2 mode */
> >> +       host->ios.timing = MMC_TIMING_LEGACY;
> >>         return err;
> >>  }
> >
> > I wouldn't mind changing to the above. But, maybe an even better
> > option is to use the ->timing variable in the struct sdhci_host, as
> > it's there already to keep track of the current/previous timing state.
> > Would that work too?
>
> The host does not really have enough information.

Okay, let's go with the approach you suggested above/below then!

>
> >
> >>
> >> diff --git a/drivers/mmc/host/sdhci-uhs2.c b/drivers/mmc/host/sdhci-uhs2.c
> >> index 517c497112f4..d1f3318b7d3a 100644
> >> --- a/drivers/mmc/host/sdhci-uhs2.c
> >> +++ b/drivers/mmc/host/sdhci-uhs2.c
> >> @@ -267,10 +267,11 @@ static void __sdhci_uhs2_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
> >>
> >>         /* UHS2 timing. Note, UHS2 timing is disabled when powering off */
> >>         ctrl_2 = sdhci_readw(host, SDHCI_HOST_CONTROL2);
> >> -       if (ios->timing == MMC_TIMING_UHS2_SPEED_A ||
> >> -           ios->timing == MMC_TIMING_UHS2_SPEED_A_HD ||
> >> -           ios->timing == MMC_TIMING_UHS2_SPEED_B ||
> >> -           ios->timing == MMC_TIMING_UHS2_SPEED_B_HD)
> >> +       if (ios->power_mode != MMC_POWER_OFF &&
> >> +           (ios->timing == MMC_TIMING_UHS2_SPEED_A ||
> >> +            ios->timing == MMC_TIMING_UHS2_SPEED_A_HD ||
> >> +            ios->timing == MMC_TIMING_UHS2_SPEED_B ||
> >> +            ios->timing == MMC_TIMING_UHS2_SPEED_B_HD))
> >>                 ctrl_2 |= SDHCI_CTRL_UHS2 | SDHCI_CTRL_UHS2_ENABLE;
> >>         else
> >>                 ctrl_2 &= ~(SDHCI_CTRL_UHS2 | SDHCI_CTRL_UHS2_ENABLE);
> >>
> >>

Kind regards
Uffe