linux-kernel - Re: [PATCH] mmc: sdhci: do not try to use 3.3V signaling if not supported

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Date:   Thu, 5 Jul 2018 15:10:08 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Stefan Agner <stefan@...er.ch>
Cc:     Adrian Hunter <adrian.hunter@...el.com>, marcel@...wiler.com,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc: sdhci: do not try to use 3.3V signaling if not supported

On 5 July 2018 at 14:18, Stefan Agner <stefan@...er.ch> wrote:
> For eMMC devices it is valid to only support 1.8V signaling. When
> vqmmc is set to a fixed 1.8V regulator the stack tries to set 3.3V
> initially and prints the following warning:
>    mmc1: Switching to 3.3V signalling voltage failed
>
> Clear the MMC_SIGNAL_VOLTAGE_330 flag in case 3.3V is signaling is
> not available. This prevents the stack from even trying to use
> 3.3V signaling and avoids the above warning.
>
> Signed-off-by: Stefan Agner <stefan@...er.ch>

Thanks, applied for next!

Kind regards
Uffe

> ---
>  drivers/mmc/host/sdhci.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 1c828e0e9905..a7b5602ef6f7 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -3734,14 +3734,21 @@ int sdhci_setup_host(struct sdhci_host *host)
>             mmc_gpio_get_cd(host->mmc) < 0)
>                 mmc->caps |= MMC_CAP_NEEDS_POLL;
>
> -       /* If vqmmc regulator and no 1.8V signalling, then there's no UHS */
>         if (!IS_ERR(mmc->supply.vqmmc)) {
>                 ret = regulator_enable(mmc->supply.vqmmc);
> +
> +               /* If vqmmc provides no 1.8V signalling, then there's no UHS */
>                 if (!regulator_is_supported_voltage(mmc->supply.vqmmc, 1700000,
>                                                     1950000))
>                         host->caps1 &= ~(SDHCI_SUPPORT_SDR104 |
>                                          SDHCI_SUPPORT_SDR50 |
>                                          SDHCI_SUPPORT_DDR50);
> +
> +               /* In eMMC case vqmmc might be a fixed 1.8V regulator */
> +               if (!regulator_is_supported_voltage(mmc->supply.vqmmc, 2700000,
> +                                                   3600000))
> +                       host->flags &= ~SDHCI_SIGNALING_330;
> +
>                 if (ret) {
>                         pr_warn("%s: Failed to enable vqmmc regulator: %d\n",
>                                 mmc_hostname(mmc), ret);
> --
> 2.18.0
>