linux-kernel - Re: [PATCH V12 12/23] mmc: sdhci-uhs2: skip signal_voltage

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Message-ID: <CAK00qKCAoousoi0Ly84Mvnycv99bizMmpAxRH1abpuGPT7VWEw@mail.gmail.com>
Date:   Fri, 17 Nov 2023 18:49:57 +0800
From:   Victor Shih <victorshihgli@...il.com>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org, benchuanggli@...il.com,
        HL.Liu@...esyslogic.com.tw, Greg.tu@...esyslogic.com.tw,
        takahiro.akashi@...aro.org, dlunev@...omium.org,
        Ben Chuang <ben.chuang@...esyslogic.com.tw>,
        Victor Shih <victor.shih@...esyslogic.com.tw>
Subject: Re: [PATCH V12 12/23] mmc: sdhci-uhs2: skip signal_voltage_switch()

On Fri, Oct 6, 2023 at 6:51 PM Adrian Hunter <adrian.hunter@...el.com> wrote:
>
> On 6/10/23 13:30, Victor Shih wrote:
> > On Tue, Oct 3, 2023 at 5:58 PM Ulf Hansson <ulf.hansson@...aro.org> wrote:
> >>
> >> On Fri, 15 Sept 2023 at 11:44, Victor Shih <victorshihgli@...il.com> wrote:
> >>>
> >>> From: Victor Shih <victor.shih@...esyslogic.com.tw>
> >>>
> >>> For UHS2, the signal voltage is supplied by vdd2 which is already 1.8v,
> >>> so no voltage switch required.
> >>
> >> Can you please elaborate on this? I don't get anything of the above, sorry.
> >>
> >>>
> >>> Signed-off-by: Ben Chuang <ben.chuang@...esyslogic.com.tw>
> >>> Signed-off-by: AKASHI Takahiro <takahiro.akashi@...aro.org>
> >>> Signed-off-by: Victor Shih <victor.shih@...esyslogic.com.tw>
> >>> Acked-by: Adrian Hunter <adrian.hunter@...el.com>
> >>> ---
> >>>
> >>> Updates in V5:
> >>>  - Use sdhci_uhs2_mode() to simplify code in
> >>>    sdhci_uhs2_start_signal_voltage_switch().
> >>>
> >>> ---
> >>>
> >>>  drivers/mmc/host/sdhci-uhs2.c | 24 ++++++++++++++++++++++++
> >>>  1 file changed, 24 insertions(+)
> >>>
> >>> diff --git a/drivers/mmc/host/sdhci-uhs2.c b/drivers/mmc/host/sdhci-uhs2.c
> >>> index fc37a34629c2..92fb69b7e209 100644
> >>> --- a/drivers/mmc/host/sdhci-uhs2.c
> >>> +++ b/drivers/mmc/host/sdhci-uhs2.c
> >>> @@ -142,6 +142,27 @@ static void sdhci_uhs2_set_power(struct sdhci_host *host, unsigned char mode, un
> >>>         }
> >>>  }
> >>>
> >>> +/*****************************************************************************\
> >>> + *                                                                           *
> >>> + * MMC callbacks                                                             *
> >>> + *                                                                           *
> >>> +\*****************************************************************************/
> >>> +
> >>> +static int sdhci_uhs2_start_signal_voltage_switch(struct mmc_host *mmc,
> >>> +                                                 struct mmc_ios *ios)
> >>> +{
> >>> +       struct sdhci_host *host = mmc_priv(mmc);
> >>> +
> >>> +       /*
> >>> +        * For UHS2, the signal voltage is supplied by vdd2 which is
> >>> +        * already 1.8v so no voltage switch required.
> >>> +        */
> >>> +       if (sdhci_uhs2_mode(host))
> >>> +               return 0;
> >>
> >> This is just wrong. If we are initializing a uhs2 card, we certainly
> >> should call ->start_signal_voltage_switch() callback at all. This is
> >> for UHS-I cards, right?
> >>
> >
> > Hi, Ulf
> >
> > UHS-II does not need single_voltage.
> > I will modify the commit message in the next version.
> > sdhci_uhs2_start_signal_voltage_switch() is under
> > mmc_host_ops.start_signal_voltage_switch host ops,
> > therefore, we need to keep the UHS-I path here.
>
> You should be able to leave out the patch entirely
> because ->start_signal_voltage_switch() is not called
> for UHS2 mode
>

Hi, Ulf and Adrian

I will drop this patch in version 13.

Thanks, Victor Shih

> >
> > Thanks, Victor Shih
> >
> >>> +
> >>> +       return sdhci_start_signal_voltage_switch(mmc, ios);
> >>> +}
> >>> +
> >>>  /*****************************************************************************\
> >>>   *                                                                           *
> >>>   * Driver init/exit                                                          *
> >>> @@ -150,6 +171,9 @@ static void sdhci_uhs2_set_power(struct sdhci_host *host, unsigned char mode, un
> >>>
> >>>  static int sdhci_uhs2_host_ops_init(struct sdhci_host *host)
> >>>  {
> >>> +       host->mmc_host_ops.start_signal_voltage_switch =
> >>> +               sdhci_uhs2_start_signal_voltage_switch;
> >>> +
> >>>         return 0;
> >>>  }
> >>>
> >>
> >> Kind regards
> >> Uffe
>