Re: [RFC PATCH V3 12/21] mmc: sdhci: UHS-II support, add hooks for additional operations

[Ben Chuang]

On Fri, Sep 18, 2020 at 2:38 PM AKASHI Takahiro
<takahiro.akashi@xxxxxxxxxx> wrote:
>
> Adrian, Ben,
>
> Regarding _set_ios() function,
>
> On Fri, Aug 21, 2020 at 05:08:32PM +0300, Adrian Hunter wrote:
> > On 10/07/20 2:10 pm, Ben Chuang wrote:
> > > From: Ben Chuang <ben.chuang@xxxxxxxxxxxxxxxxxxx>
> > >
> > > In this commit, UHS-II related operations will be called via a function
> > > pointer array, sdhci_uhs2_ops, in order to make UHS-II support as
> > > a kernel module.
> > > This array will be initialized only if CONFIG_MMC_SDHCI_UHS2 is enabled
> > > and when the UHS-II module is loaded. Otherwise, all the functions
> > > stay void.
> > >
> > > Signed-off-by: Ben Chuang <ben.chuang@xxxxxxxxxxxxxxxxxxx>
> > > Signed-off-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
>
>   (snip)
>
> > > @@ -2261,6 +2324,7 @@ void sdhci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
> > >  {
> > >     struct sdhci_host *host = mmc_priv(mmc);
> > >     u8 ctrl;
> > > +   u16 ctrl_2;
> > >
> > >     if (ios->power_mode == MMC_POWER_UNDEFINED)
> > >             return;
> > > @@ -2287,6 +2351,10 @@ void sdhci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
> > >             sdhci_enable_preset_value(host, false);
> > >
> > >     if (!ios->clock || ios->clock != host->clock) {
> > > +           if (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> > > +               ios->timing == MMC_TIMING_UHS2)
> > > +                   host->timing = ios->timing;
> > > +
> > >             host->ops->set_clock(host, ios->clock);
> > >             host->clock = ios->clock;
> > >
> > > @@ -2308,6 +2376,18 @@ void sdhci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
> > >     else
> > >             sdhci_set_power(host, ios->power_mode, ios->vdd);
> > >
> > > +   /* 4.0 host support */
> > > +   if (host->version >= SDHCI_SPEC_400) {
> > > +           /* UHS2 Support */
> > > +           if (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> > > +               host->mmc->flags & MMC_UHS2_SUPPORT &&
> > > +               host->mmc->caps & MMC_CAP_UHS2) {
> > > +                   if (sdhci_uhs2_ops.do_set_ios)
> > > +                           sdhci_uhs2_ops.do_set_ios(host, ios);
> > > +                   return;
> > > +           }
> > > +   }
> > > +
> >
> > Please look at using existing callbacks instead, maybe creating uhs2_set_ios(), uhs2_set_clock(), uhs2_set_power()
>
> I think that we will create uhs2_set_ios() (and uhs2_set_power()
> as we discussed on patch#15/21), but not uhs_set_clock().
>
> Since we have a hook only in struct mmc_host_ops, but not in struct
> sdhci_ops, all the drivers who want to support UHS-II need to
> set host->mmc_host_ops->set_ios to sdhci_uhs2_set_ios explicitly
> in their own init (or probe) function.
> (Again, sdhci_uhs2_set_ios() seems to be generic though.)
>
> Is this okay for you?
>         -> Adrian
>
> During refactoring the code, I found that sdhci_set_power() is called
> twice in sdhci_set_ios():
>         sdhci_set_ios(host, power_mode, vdd1, -1); in sdhci_set_ios(), and
>         sdhci_set_ios(host, power_mode, vdd1, vdd2) in ush2_do_set_ios()
>
> Can you please confirm that those are redundant?

Yes, uhs2 set power is independent with uhs1.
But set  uhs2 power process  should meet  uhs2 spec.

>         -> Ben
>
> I also wonder why we need spin locks in uhs2_do_set_ios() while
> not in sdhci_set_ios().

You can check if  spin locks in uhs2_do_set_ios() is necessary.
If set/clear irq can be execute safely without spin locks, you can
remove spin locks.

>
>         -> Ben
>
> -Takahiro Akashi