Re: [PATCH v4 4/4] mmc: sdhci-of-arasan: Enable UHS-1 support for Keem Bay SOC

[Ulf Hansson]

On Thu, 8 Oct 2020 at 04:12, <muhammad.husaini.zulkifli@xxxxxxxxx> wrote:
>
> From: Muhammad Husaini Zulkifli <muhammad.husaini.zulkifli@xxxxxxxxx>
>
> Voltage switching sequence is needed to support UHS-1 interface.
> There are 2 places to control the voltage.
> 1) By setting the AON register using firmware driver calling
> system-level platform management layer (SMC) to set the register.
> 2) By controlling the GPIO expander value to drive either 1.8V or 3.3V
> for power mux input.
>
> Signed-off-by: Muhammad Husaini Zulkifli <muhammad.husaini.zulkifli@xxxxxxxxx>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxx>
> Reviewed-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> ---
>  drivers/mmc/host/sdhci-of-arasan.c | 126 +++++++++++++++++++++++++++++
>  1 file changed, 126 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci-of-arasan.c b/drivers/mmc/host/sdhci-of-arasan.c
> index 46aea6516133..ea2467b0073d 100644
> --- a/drivers/mmc/host/sdhci-of-arasan.c
> +++ b/drivers/mmc/host/sdhci-of-arasan.c
> @@ -16,6 +16,7 @@
>   */
>
>  #include <linux/clk-provider.h>
> +#include <linux/gpio/consumer.h>
>  #include <linux/mfd/syscon.h>
>  #include <linux/module.h>
>  #include <linux/of_device.h>
> @@ -23,6 +24,7 @@
>  #include <linux/regmap.h>
>  #include <linux/of.h>
>  #include <linux/firmware/xlnx-zynqmp.h>
> +#include <linux/firmware/intel/keembay_firmware.h>
>
>  #include "cqhci.h"
>  #include "sdhci-pltfm.h"
> @@ -136,6 +138,7 @@ struct sdhci_arasan_clk_data {
>   * @soc_ctl_base:      Pointer to regmap for syscon for soc_ctl registers.
>   * @soc_ctl_map:       Map to get offsets into soc_ctl registers.
>   * @quirks:            Arasan deviations from spec.
> + * @uhs_gpio:          Pointer to the uhs gpio.
>   */
>  struct sdhci_arasan_data {
>         struct sdhci_host *host;
> @@ -150,6 +153,7 @@ struct sdhci_arasan_data {
>         struct regmap   *soc_ctl_base;
>         const struct sdhci_arasan_soc_ctl_map *soc_ctl_map;
>         unsigned int    quirks;
> +       struct gpio_desc *uhs_gpio;
>
>  /* Controller does not have CD wired and will not function normally without */
>  #define SDHCI_ARASAN_QUIRK_FORCE_CDTEST        BIT(0)
> @@ -361,6 +365,112 @@ static int sdhci_arasan_voltage_switch(struct mmc_host *mmc,
>         return -EINVAL;
>  }
>
> +static int sdhci_arasan_keembay_voltage_switch(struct mmc_host *mmc,
> +                                      struct mmc_ios *ios)
> +{
> +       struct sdhci_host *host = mmc_priv(mmc);
> +       struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +       struct sdhci_arasan_data *sdhci_arasan = sdhci_pltfm_priv(pltfm_host);
> +       u16 ctrl_2, clk;
> +       int ret;
> +
> +       switch (ios->signal_voltage) {
> +       case MMC_SIGNAL_VOLTAGE_180:
> +               clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> +               clk &= ~SDHCI_CLOCK_CARD_EN;
> +               sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
> +
> +               clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> +               if (clk & SDHCI_CLOCK_CARD_EN)
> +                       return -EAGAIN;
> +
> +               sdhci_writeb(host, SDHCI_POWER_ON | SDHCI_POWER_180,
> +                                  SDHCI_POWER_CONTROL);
> +
> +               /*
> +                * Set VDDIO_B voltage to Low for 1.8V
> +                * which is controlling by GPIO Expander.
> +                */
> +               gpiod_set_value_cansleep(sdhci_arasan->uhs_gpio, 0);
> +
> +               /*
> +                * This is like a final gatekeeper. Need to ensure changed voltage
> +                * is settled before and after turn on this bit.
> +                */
> +               usleep_range(1000, 1100);
> +
> +               ret = keembay_sd_voltage_selection(KEEMBAY_SET_1V8_VOLT);
> +               if (ret)
> +                       return ret;
> +
> +               usleep_range(1000, 1100);

No, sorry, but I don't like this.

This looks like a GPIO regulator with an extension of using the
keembay_sd_voltage_selection() thingy. I think you can model these
things behind a regulator and hook it up as a vqmmc supply in DT
instead. BTW, this is the common way we deal with these things for mmc
host drivers.

> +
> +               ctrl_2 = sdhci_readw(host, SDHCI_HOST_CONTROL2);
> +               ctrl_2 |= SDHCI_CTRL_VDD_180;
> +               sdhci_writew(host, ctrl_2, SDHCI_HOST_CONTROL2);
> +
> +               /* Sleep for 5ms to stabilize 1.8V regulator */
> +               usleep_range(5000, 5500);
> +
> +               /* 1.8V regulator output should be stable within 5 ms */
> +               ctrl_2 = sdhci_readw(host, SDHCI_HOST_CONTROL2);
> +               if (!(ctrl_2 & SDHCI_CTRL_VDD_180))
> +                       return -EAGAIN;
> +
> +               clk  = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> +               clk |= SDHCI_CLOCK_CARD_EN;
> +               sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
> +               break;
> +       case MMC_SIGNAL_VOLTAGE_330:
> +               /*
> +                * Set VDDIO_B voltage to High for 3.3V
> +                * which is controlling by GPIO Expander.
> +                */
> +               gpiod_set_value_cansleep(sdhci_arasan->uhs_gpio, 1);
> +
> +               /*
> +                * This is like a final gatekeeper. Need to ensure changed voltage
> +                * is settled before and after turn on this bit.
> +                */
> +               usleep_range(1000, 1100);
> +
> +               ret = keembay_sd_voltage_selection(KEEMBAY_SET_3V3_VOLT);
> +               if (ret)
> +                       return ret;
> +
> +               usleep_range(1000, 1100);
> +
> +               /* Set 1.8V Signal Enable in the Host Control2 register to 0 */
> +               ctrl_2 = sdhci_readw(host, SDHCI_HOST_CONTROL2);
> +               ctrl_2 &= ~SDHCI_CTRL_VDD_180;
> +               sdhci_writew(host, ctrl_2, SDHCI_HOST_CONTROL2);
> +
> +               /* Sleep for 5ms to stabilize 3.3V regulator */
> +               usleep_range(5000, 5500);
> +
> +               /* 3.3V regulator output should be stable within 5 ms */
> +               ctrl_2 = sdhci_readw(host, SDHCI_HOST_CONTROL2);
> +               if (ctrl_2 & SDHCI_CTRL_VDD_180)
> +                       return -EAGAIN;
> +
> +               break;
> +       default:
> +               return -EINVAL;
> +       }
> +
> +       return 0;
> +}
> +
> +static int sdhci_arasan_keembay_select_drive_strength(struct mmc_card *card,
> +                                       unsigned int max_dtr, int host_drv,
> +                                       int card_drv, int *drv_type)
> +{
> +       if (card->host->ios.signal_voltage == MMC_SIGNAL_VOLTAGE_180)
> +               *drv_type = MMC_SET_DRIVER_TYPE_C;
> +
> +       return 0;
> +}
> +
>  static const struct sdhci_ops sdhci_arasan_ops = {
>         .set_clock = sdhci_arasan_set_clock,
>         .get_max_clock = sdhci_pltfm_clk_get_max_clock,
> @@ -1601,6 +1711,22 @@ static int sdhci_arasan_probe(struct platform_device *pdev)
>                 host->mmc->caps |= MMC_CAP_WAIT_WHILE_BUSY;
>         }
>
> +       if (of_device_is_compatible(np, "intel,keembay-sdhci-5.1-sd")) {
> +               struct gpio_desc *uhs;
> +
> +               uhs = devm_gpiod_get_optional(dev, "uhs", GPIOD_OUT_HIGH);
> +               if (IS_ERR(uhs))
> +                       return dev_err_probe(dev, PTR_ERR(uhs), "can't get uhs gpio\n");
> +
> +               sdhci_arasan->uhs_gpio = uhs;
> +
> +               host->mmc_host_ops.start_signal_voltage_switch =
> +                       sdhci_arasan_keembay_voltage_switch;
> +
> +               host->mmc_host_ops.select_drive_strength =
> +                       sdhci_arasan_keembay_select_drive_strength;
> +       }
> +
>         sdhci_arasan_update_baseclkfreq(host);
>
>         ret = sdhci_arasan_register_sdclk(sdhci_arasan, clk_xin, &pdev->dev);
> --
> 2.17.1
>

Kind regards
Uffe