[Linux-stm32] [PATCH V2 2/4] mmc: mmci: Add support for probing bus voltage level translator

[Ulf Hansson]

On Sun, 24 Jan 2021 at 18:03, Marek Vasut <marex at denx.de> wrote:
>
> Add support for testing whether bus voltage level translator is present
> and operational. This is useful on systems where the bus voltage level
> translator is optional, as the translator can be auto-detected by the
> driver and the feedback clock functionality can be disabled if it is
> not present.
>
> This requires additional pinmux state, "init", where the CMD, CK, CKIN
> lines are not configured, so they can be claimed as GPIOs early on in
> probe(). The translator test sets CMD high to avoid interfering with a
> card, and then verifies whether signal set on CK is detected on CKIN.
> If the signal is detected, translator is present, otherwise the CKIN
> feedback clock are disabled.
>
> Tested-by: Yann Gautier <yann.gautier at foss.st.com>
> Reviewed-by: Linus Walleij <linus.walleij at linaro.org>
> Signed-off-by: Marek Vasut <marex at denx.de>
> Cc: Alexandre Torgue <alexandre.torgue at st.com>
> Cc: Linus Walleij <linus.walleij at linaro.org>
> Cc: Ludovic Barre <ludovic.barre at st.com>
> Cc: Ulf Hansson <ulf.hansson at linaro.org>
> Cc: linux-stm32 at st-md-mailman.stormreply.com

Applied for next, thanks!

Kind regards
Uffe


> ---
> V2: Rebase on next-20210122, add TB and RB
> ---
>  drivers/mmc/host/mmci.c | 70 ++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 65 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
> index b5a41a7ce165..1bc674577ff9 100644
> --- a/drivers/mmc/host/mmci.c
> +++ b/drivers/mmc/host/mmci.c
> @@ -36,6 +36,7 @@
>  #include <linux/types.h>
>  #include <linux/pinctrl/consumer.h>
>  #include <linux/reset.h>
> +#include <linux/gpio/consumer.h>
>
>  #include <asm/div64.h>
>  #include <asm/io.h>
> @@ -1888,6 +1889,65 @@ static struct mmc_host_ops mmci_ops = {
>         .start_signal_voltage_switch = mmci_sig_volt_switch,
>  };
>
> +static void mmci_probe_level_translator(struct mmc_host *mmc)
> +{
> +       struct device *dev = mmc_dev(mmc);
> +       struct mmci_host *host = mmc_priv(mmc);
> +       struct gpio_desc *cmd_gpio;
> +       struct gpio_desc *ck_gpio;
> +       struct gpio_desc *ckin_gpio;
> +       int clk_hi, clk_lo;
> +
> +       /*
> +        * Assume the level translator is present if st,use-ckin is set.
> +        * This is to cater for DTs which do not implement this test.
> +        */
> +       host->clk_reg_add |= MCI_STM32_CLK_SELCKIN;
> +
> +       cmd_gpio = gpiod_get(dev, "st,cmd", GPIOD_OUT_HIGH);
> +       if (IS_ERR(cmd_gpio))
> +               goto exit_cmd;
> +
> +       ck_gpio = gpiod_get(dev, "st,ck", GPIOD_OUT_HIGH);
> +       if (IS_ERR(ck_gpio))
> +               goto exit_ck;
> +
> +       ckin_gpio = gpiod_get(dev, "st,ckin", GPIOD_IN);
> +       if (IS_ERR(ckin_gpio))
> +               goto exit_ckin;
> +
> +       /* All GPIOs are valid, test whether level translator works */
> +
> +       /* Sample CKIN */
> +       clk_hi = !!gpiod_get_value(ckin_gpio);
> +
> +       /* Set CK low */
> +       gpiod_set_value(ck_gpio, 0);
> +
> +       /* Sample CKIN */
> +       clk_lo = !!gpiod_get_value(ckin_gpio);
> +
> +       /* Tristate all */
> +       gpiod_direction_input(cmd_gpio);
> +       gpiod_direction_input(ck_gpio);
> +
> +       /* Level translator is present if CK signal is propagated to CKIN */
> +       if (!clk_hi || clk_lo) {
> +               host->clk_reg_add &= ~MCI_STM32_CLK_SELCKIN;
> +               dev_warn(dev,
> +                        "Level translator inoperable, CK signal not detected on CKIN, disabling.\n");
> +       }
> +
> +       gpiod_put(ckin_gpio);
> +
> +exit_ckin:
> +       gpiod_put(ck_gpio);
> +exit_ck:
> +       gpiod_put(cmd_gpio);
> +exit_cmd:
> +       pinctrl_select_default_state(dev);
> +}
> +
>  static int mmci_of_parse(struct device_node *np, struct mmc_host *mmc)
>  {
>         struct mmci_host *host = mmc_priv(mmc);
> @@ -1913,7 +1973,7 @@ static int mmci_of_parse(struct device_node *np, struct mmc_host *mmc)
>         if (of_get_property(np, "st,neg-edge", NULL))
>                 host->clk_reg_add |= MCI_STM32_CLK_NEGEDGE;
>         if (of_get_property(np, "st,use-ckin", NULL))
> -               host->clk_reg_add |= MCI_STM32_CLK_SELCKIN;
> +               mmci_probe_level_translator(mmc);
>
>         if (of_get_property(np, "mmc-cap-mmc-highspeed", NULL))
>                 mmc->caps |= MMC_CAP_MMC_HIGHSPEED;
> @@ -1949,15 +2009,15 @@ static int mmci_probe(struct amba_device *dev,
>         if (!mmc)
>                 return -ENOMEM;
>
> -       ret = mmci_of_parse(np, mmc);
> -       if (ret)
> -               goto host_free;
> -
>         host = mmc_priv(mmc);
>         host->mmc = mmc;
>         host->mmc_ops = &mmci_ops;
>         mmc->ops = &mmci_ops;
>
> +       ret = mmci_of_parse(np, mmc);
> +       if (ret)
> +               goto host_free;
> +
>         /*
>          * Some variant (STM32) doesn't have opendrain bit, nevertheless
>          * pins can be set accordingly using pinctrl
> --
> 2.29.2
>