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

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Message-ID: <CAPDyKFpzuds6Ttbhw1cqZwisa+M6167DT3DUihcDqFjYJX95eA@mail.gmail.com>
Date:   Tue, 3 Oct 2023 11:58:17 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Victor Shih <victorshihgli@...il.com>
Cc:     adrian.hunter@...el.com, 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, 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?

> +
> +       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