Re: [PATCH v2 2/7] mmc: sdhci-of-k1: add regulator and pinctrl voltage switching support

[Yixun Lan <dlan@kernel.org>]

Hi Iker,

On 12:40 Mon 09 Mar     , 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.
> 
> Signed-off-by: Iker Pedrosa <ikerpedrosam@gmail.com>
> ---
>  drivers/mmc/host/sdhci-of-k1.c | 59 ++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 59 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-of-k1.c b/drivers/mmc/host/sdhci-of-k1.c
> index 585c7eca6ebf253aac466dd37cef029deb63f692..8af117a8e271c04a80d8dc7bb5ce12075652dd7a 100644
> --- a/drivers/mmc/host/sdhci-of-k1.c
> +++ b/drivers/mmc/host/sdhci-of-k1.c
> @@ -15,6 +15,7 @@
>  #include <linux/module.h>
>  #include <linux/of.h>
>  #include <linux/of_device.h>
> +#include <linux/pinctrl/consumer.h>
>  #include <linux/platform_device.h>
>  
>  #include "sdhci.h"
> @@ -70,6 +71,9 @@
>  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 */
> @@ -218,6 +222,42 @@ static void spacemit_sdhci_pre_hs400_to_hs200(struct mmc_host *mmc)
>  			       SPACEMIT_SDHC_PHY_CTRL_REG);
>  }
>  
> +static void spacemit_sdhci_voltage_switch(struct sdhci_host *host)
> +{
> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +	struct spacemit_sdhci_host *sdhst = sdhci_pltfm_priv(pltfm_host);
> +	struct mmc_ios *ios = &host->mmc->ios;
> +	struct pinctrl_state *state;
> +	int ret;
> +
> +	/* Select appropriate pinctrl state based on signal voltage */
> +	if (sdhst->pinctrl) {
do a sanity check, then abort it early, the advantage is that you can get rid of
one indetation for next code..

	if (!sdhst->pinctrl)
		return;


> +		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(host->mmc), "unsupported voltage %d\n",
> +				 ios->signal_voltage);
> +			return;
> +		}
> +
> +		if (state) {
> +			ret = pinctrl_select_state(sdhst->pinctrl, state);
> +			if (ret) {
> +				dev_warn(mmc_dev(host->mmc),
> +					 "failed to select pinctrl state: %d\n", ret);
> +				return;
> +			}
> +			dev_dbg(mmc_dev(host->mmc), "switched to %s pinctrl state\n",
> +				ios->signal_voltage == MMC_SIGNAL_VOLTAGE_180 ? "UHS" : "default");
> +		}
> +	}
> +}
> +
>  static inline int spacemit_sdhci_get_clocks(struct device *dev,
>  					    struct sdhci_pltfm_host *pltfm_host)
>  {
> @@ -242,6 +282,7 @@ static const struct sdhci_ops spacemit_sdhci_ops = {
>  	.set_bus_width		= sdhci_set_bus_width,
>  	.set_clock		= spacemit_sdhci_set_clock,
>  	.set_uhs_signaling	= spacemit_sdhci_set_uhs_signaling,
> +	.voltage_switch         = spacemit_sdhci_voltage_switch,
>  };
>  
>  static const struct sdhci_pltfm_data spacemit_sdhci_k1_pdata = {
> @@ -293,6 +334,24 @@ static int spacemit_sdhci_probe(struct platform_device *pdev)
>  
>  	host->mmc->caps |= MMC_CAP_NEED_RSP_BUSY;
>  
> +	sdhst = sdhci_pltfm_priv(pltfm_host);
..
> +	sdhst->pinctrl = devm_pinctrl_get(dev);
> +	if (!IS_ERR(sdhst->pinctrl)) {
> +		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);
> +	} else {
> +		sdhst->pinctrl = NULL;
> +		dev_dbg(dev, "pinctrl not available, voltage switching will work without it\n");
> +	}
> +
how about creating a function spacemit_sdhci_get_pins()? similar as get
resource for clock, will more readable.

>  	ret = spacemit_sdhci_get_clocks(dev, pltfm_host);
>  	if (ret)
>  		goto err_pltfm;
> 
> -- 
> 2.53.0
> 

-- 
Yixun Lan (dlan)