linux-kernel - Re: [RFC PATCH v3.1 14/27] mmc: sdhci-uhs2: skip signal_voltage

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Message-ID: <d2bb08b8-b3d0-3956-70ff-a21ab8a0fe30@intel.com>
Date:   Thu, 26 Nov 2020 10:16:44 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     AKASHI Takahiro <takahiro.akashi@...aro.org>,
        ulf.hansson@...aro.org
Cc:     linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        ben.chuang@...esyslogic.com.tw, greg.tu@...esyslogic.com.tw
Subject: Re: [RFC PATCH v3.1 14/27] mmc: sdhci-uhs2: skip
 signal_voltage_switch()

On 6/11/20 4:27 am, AKASHI Takahiro wrote:
> For UHS2, the signal voltage is supplied by vdd2 which is already 1.8v,
> so no voltage switch required.
> 
> Signed-off-by: Ben Chuang <ben.chuang@...esyslogic.com.tw>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi@...aro.org>
> ---
>  drivers/mmc/host/sdhci-uhs2.c | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-uhs2.c b/drivers/mmc/host/sdhci-uhs2.c
> index 2bf78cc4e9ed..1eca89359351 100644
> --- a/drivers/mmc/host/sdhci-uhs2.c
> +++ b/drivers/mmc/host/sdhci-uhs2.c
> @@ -178,6 +178,29 @@ void sdhci_uhs2_set_power(struct sdhci_host *host, unsigned char mode,
>  }
>  EXPORT_SYMBOL_GPL(sdhci_uhs2_set_power);
>  
> +/*****************************************************************************\
> + *                                                                           *
> + * 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 (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> +             host->version >= SDHCI_SPEC_400 &&
> +             host->mmc->flags & MMC_UHS2_SUPPORT)

Could this be the same helper function suggested elsewhere i.e.

	if (!sdhci_uhs2_mode(host))

> +                return 0;
> +
> +	return sdhci_start_signal_voltage_switch(mmc, ios);
> +}
> +
>  /*****************************************************************************\
>   *                                                                           *
>   * Driver init/exit                                                          *
> @@ -186,6 +209,9 @@ EXPORT_SYMBOL_GPL(sdhci_uhs2_set_power);
>  
>  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;
>  }
>  
>