Re: [PATCH v4 2/8] mmc: sdhci-of-k1: add regulator and pinctrl voltage switching support

[Adrian Hunter <adrian.hunter@intel.com>]

On 23/03/2026 12:19, Iker Pedrosa wrote:
> Add voltage switching infrastructure for UHS-I modes by integrating both
> regulator framework (for supply voltage control) and pinctrl state
> switching (for pin drive strength optimization).
> 
> - Add regulator supply parsing and voltage switching callback
> - Add optional pinctrl state switching between "default" (3.3V) and
>   "state_uhs" (1.8V) configurations
> - Enable coordinated voltage and pin configuration changes for UHS modes
> 
> This provides complete voltage switching support while maintaining
> backward compatibility when pinctrl states are not defined.
> 
> Tested-by: Anand Moon <linux.amoon@gmail.com>
> Tested-by: Trevor Gamblin <tgamblin@baylibre.com>
> Signed-off-by: Iker Pedrosa <ikerpedrosam@gmail.com>

Acked-by: Adrian Hunter <adrian.hunter@intel.com>

> ---
>  drivers/mmc/host/sdhci-of-k1.c | 72 ++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 72 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-of-k1.c b/drivers/mmc/host/sdhci-of-k1.c
> index 0dd06fc19b8574ae1b00f7e5d09b7d4c87d06770..234e258af25996e7bbcd0b70366c7480bf62bee7 100644
> --- a/drivers/mmc/host/sdhci-of-k1.c
> +++ b/drivers/mmc/host/sdhci-of-k1.c
> @@ -16,6 +16,7 @@
>  #include <linux/of.h>
>  #include <linux/of_device.h>
>  #include <linux/reset.h>
> +#include <linux/pinctrl/consumer.h>
>  #include <linux/platform_device.h>
>  
>  #include "sdhci.h"
> @@ -71,6 +72,9 @@
>  struct spacemit_sdhci_host {
>  	struct clk *clk_core;
>  	struct clk *clk_io;
> +	struct pinctrl *pinctrl;
> +	struct pinctrl_state *pinctrl_default;
> +	struct pinctrl_state *pinctrl_uhs;
>  };
>  
>  /* All helper functions will update clr/set while preserve rest bits */
> @@ -219,6 +223,46 @@ static void spacemit_sdhci_pre_hs400_to_hs200(struct mmc_host *mmc)
>  			       SPACEMIT_SDHC_PHY_CTRL_REG);
>  }
>  
> +static int spacemit_sdhci_start_signal_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 spacemit_sdhci_host *sdhst = sdhci_pltfm_priv(pltfm_host);
> +	struct pinctrl_state *state;
> +	int ret;
> +
> +	ret = sdhci_start_signal_voltage_switch(mmc, ios);
> +	if (ret)
> +		return ret;
> +
> +	if (!sdhst->pinctrl)
> +		return 0;
> +
> +	/* Select appropriate pinctrl state based on signal voltage */
> +	switch (ios->signal_voltage) {
> +	case MMC_SIGNAL_VOLTAGE_330:
> +		state = sdhst->pinctrl_default;
> +		break;
> +	case MMC_SIGNAL_VOLTAGE_180:
> +		state = sdhst->pinctrl_uhs;
> +		break;
> +	default:
> +		dev_warn(mmc_dev(mmc), "unsupported voltage %d\n", ios->signal_voltage);
> +		return 0;
> +	}
> +
> +	ret = pinctrl_select_state(sdhst->pinctrl, state);
> +	if (ret) {
> +		dev_warn(mmc_dev(mmc), "failed to select pinctrl state: %d\n", ret);
> +		return 0;
> +	}
> +	dev_dbg(mmc_dev(mmc), "switched to %s pinctrl state\n",
> +		ios->signal_voltage == MMC_SIGNAL_VOLTAGE_180 ? "UHS" : "default");
> +
> +	return 0;
> +}
> +
>  static inline int spacemit_sdhci_get_clocks(struct device *dev,
>  					    struct sdhci_pltfm_host *pltfm_host)
>  {
> @@ -252,6 +296,30 @@ static inline int spacemit_sdhci_get_resets(struct device *dev)
>  	return 0;
>  }
>  
> +static inline void spacemit_sdhci_get_pins(struct device *dev,
> +					   struct sdhci_pltfm_host *pltfm_host)
> +{
> +	struct spacemit_sdhci_host *sdhst = sdhci_pltfm_priv(pltfm_host);
> +
> +	sdhst->pinctrl = devm_pinctrl_get(dev);
> +	if (IS_ERR(sdhst->pinctrl)) {
> +		sdhst->pinctrl = NULL;
> +		dev_dbg(dev, "pinctrl not available, voltage switching will work without it\n");
> +		return;
> +	}
> +
> +	sdhst->pinctrl_default = pinctrl_lookup_state(sdhst->pinctrl, "default");
> +	if (IS_ERR(sdhst->pinctrl_default))
> +		sdhst->pinctrl_default = NULL;
> +
> +	sdhst->pinctrl_uhs = pinctrl_lookup_state(sdhst->pinctrl, "state_uhs");
> +	if (IS_ERR(sdhst->pinctrl_uhs))
> +		sdhst->pinctrl_uhs = NULL;
> +
> +	dev_dbg(dev, "pinctrl setup: default=%p, uhs=%p\n",
> +		sdhst->pinctrl_default, sdhst->pinctrl_uhs);
> +}
> +
>  static const struct sdhci_ops spacemit_sdhci_ops = {
>  	.get_max_clock		= spacemit_sdhci_clk_get_max_clock,
>  	.reset			= spacemit_sdhci_reset,
> @@ -324,6 +392,10 @@ static int spacemit_sdhci_probe(struct platform_device *pdev)
>  
>  	host->mmc->caps |= MMC_CAP_NEED_RSP_BUSY;
>  
> +	spacemit_sdhci_get_pins(dev, pltfm_host);
> +
> +	host->mmc_host_ops.start_signal_voltage_switch = spacemit_sdhci_start_signal_voltage_switch;
> +
>  	ret = spacemit_sdhci_get_clocks(dev, pltfm_host);
>  	if (ret)
>  		goto err_pltfm;
>