linux-kernel - Re: [PATCH 8/9] mmc: mmci: sdmmc: add voltage switch functions

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Message-ID: <CAPDyKFp1Qsb3yCoTJevHF+SEt5thVVriLfL-4UZSYsNTc0rdMQ@mail.gmail.com>
Date:   Fri, 24 Jan 2020 14:16:34 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Ludovic Barre <ludovic.barre@...com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH 8/9] mmc: mmci: sdmmc: add voltage switch functions

On Fri, 10 Jan 2020 at 14:49, Ludovic Barre <ludovic.barre@...com> wrote:
>
> To prepare the voltage switch procedure, the VSWITCHEN bit must be
> set before sending the cmd11.
> To confirm completion of voltage switch, the VSWEND flag must be
> checked.
>
> Signed-off-by: Ludovic Barre <ludovic.barre@...com>
> ---
>  drivers/mmc/host/mmci.h             |  4 +++
>  drivers/mmc/host/mmci_stm32_sdmmc.c | 40 ++++++++++++++++++++++++++++-
>  2 files changed, 43 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/mmci.h b/drivers/mmc/host/mmci.h
> index c04a144259a2..3634f98ad2d8 100644
> --- a/drivers/mmc/host/mmci.h
> +++ b/drivers/mmc/host/mmci.h
> @@ -165,6 +165,7 @@
>  /* Extended status bits for the STM32 variants */
>  #define MCI_STM32_BUSYD0       BIT(20)
>  #define MCI_STM32_BUSYD0END    BIT(21)
> +#define MCI_STM32_VSWEND       BIT(25)
>
>  #define MMCICLEAR              0x038
>  #define MCI_CMDCRCFAILCLR      (1 << 0)
> @@ -182,6 +183,9 @@
>  #define MCI_ST_SDIOITC         (1 << 22)
>  #define MCI_ST_CEATAENDC       (1 << 23)
>  #define MCI_ST_BUSYENDC                (1 << 24)
> +/* Extended clear bits for the STM32 variants */
> +#define MCI_STM32_VSWENDC      BIT(25)
> +#define MCI_STM32_CKSTOPC      BIT(26)
>
>  #define MMCIMASK0              0x03c
>  #define MCI_CMDCRCFAILMASK     (1 << 0)
> diff --git a/drivers/mmc/host/mmci_stm32_sdmmc.c b/drivers/mmc/host/mmci_stm32_sdmmc.c
> index 10059fa19f4a..9f43cf947c5f 100644
> --- a/drivers/mmc/host/mmci_stm32_sdmmc.c
> +++ b/drivers/mmc/host/mmci_stm32_sdmmc.c
> @@ -263,7 +263,9 @@ static void mmci_sdmmc_set_pwrreg(struct mmci_host *host, unsigned int pwr)
>         struct mmc_ios ios = host->mmc->ios;
>         struct sdmmc_dlyb *dlyb = host->variant_priv;
>
> -       pwr = host->pwr_reg_add;
> +       /* adds OF options and preserves voltage switch bits */
> +       pwr = host->pwr_reg_add |
> +               (host->pwr_reg & (MCI_STM32_VSWITCHEN | MCI_STM32_VSWITCH));
>
>         sdmmc_dlyb_input_ck(dlyb);
>
> @@ -454,6 +456,40 @@ static int sdmmc_execute_tuning(struct mmc_host *mmc, u32 opcode)
>         return sdmmc_dlyb_phase_tuning(host, opcode);
>  }
>
> +static void sdmmc_prep_vswitch(struct mmci_host *host)
> +{
> +       /* clear the voltage switch completion flag */
> +       writel_relaxed(MCI_STM32_VSWENDC, host->base + MMCICLEAR);
> +       /* enable Voltage switch procedure */
> +       mmci_write_pwrreg(host, host->pwr_reg | MCI_STM32_VSWITCHEN);
> +}
> +
> +static int sdmmc_vswitch(struct mmci_host *host, struct mmc_ios *ios)
> +{
> +       unsigned long flags;
> +       u32 status;
> +       int ret = 0;
> +
> +       if (ios->signal_voltage == MMC_SIGNAL_VOLTAGE_180) {
> +               spin_lock_irqsave(&host->lock, flags);
> +               mmci_write_pwrreg(host, host->pwr_reg | MCI_STM32_VSWITCH);
> +               spin_unlock_irqrestore(&host->lock, flags);
> +
> +               /* wait voltage switch completion while 10ms */
> +               ret = readl_relaxed_poll_timeout(host->base + MMCISTATUS,
> +                                                status,
> +                                                (status & MCI_STM32_VSWEND),
> +                                                10, 10000);
> +
> +               writel_relaxed(MCI_STM32_VSWENDC | MCI_STM32_CKSTOPC,
> +                              host->base + MMCICLEAR);
> +               mmci_write_pwrreg(host, host->pwr_reg &
> +                                 ~(MCI_STM32_VSWITCHEN | MCI_STM32_VSWITCH));
> +       }

Don't you need to manage things when resetting to
MMC_SIGNAL_VOLTAGE_330, which for example happens during a card
removal or at system suspend/resume?

> +
> +       return ret;
> +}
> +
>  static struct mmci_host_ops sdmmc_variant_ops = {
>         .validate_data = sdmmc_idma_validate_data,
>         .prep_data = sdmmc_idma_prep_data,
> @@ -465,6 +501,8 @@ static struct mmci_host_ops sdmmc_variant_ops = {
>         .set_clkreg = mmci_sdmmc_set_clkreg,
>         .set_pwrreg = mmci_sdmmc_set_pwrreg,
>         .busy_complete = sdmmc_busy_complete,
> +       .prep_volt_switch = sdmmc_prep_vswitch,
> +       .volt_switch = sdmmc_vswitch,
>  };
>
>  void sdmmc_variant_init(struct mmci_host *host)
> --
> 2.17.1
>

Kind regards
Uffe