Re: [PATCH v1] mmc: sdhci_am654: Add sdhci_am654_start_signal_voltage_switch

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

On 6/09/24 20:50, Judith Mendez wrote:
> The sdhci_start_signal_voltage_switch function sets
> V1P8_SIGNAL_ENA by default after switching to 1v8 signaling.
> V1P8_SIGNAL_ENA determines whether to launch cmd/data on neg
> edge or pos edge of clock.
> 
> Due to some eMMC and SD failures seen across am62x platform,
> do not set V1P8_SIGNAL_ENA by default, only enable the bit
> for devices that require this bit in order to switch to 1v8
> voltage for uhs modes.
> 
> Signed-off-by: Judith Mendez <jm@ti.com>
> ---
>  drivers/mmc/host/sdhci_am654.c | 86 ++++++++++++++++++++++++++++++++++
>  1 file changed, 86 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci_am654.c b/drivers/mmc/host/sdhci_am654.c
> index 0aa3c40ea6ed8..fb6232e56606b 100644
> --- a/drivers/mmc/host/sdhci_am654.c
> +++ b/drivers/mmc/host/sdhci_am654.c
> @@ -155,6 +155,7 @@ struct sdhci_am654_data {
>  	u32 tuning_loop;
>  
>  #define SDHCI_AM654_QUIRK_FORCE_CDTEST BIT(0)
> +#define SDHCI_AM654_QUIRK_SET_V1P8_ENA BIT(1)

It would be better for the quirk to represent the deviation
from normal i.e. 

#define SDHCI_AM654_QUIRK_SUPPRESS_V1P8_ENA BIT(1)

>  };
>  
>  struct window {
> @@ -356,6 +357,79 @@ static void sdhci_j721e_4bit_set_clock(struct sdhci_host *host,
>  	sdhci_set_clock(host, clock);
>  }
>  
> +int sdhci_am654_start_signal_voltage_switch(struct mmc_host *mmc,
> +					    struct mmc_ios *ios)

Simpler to call sdhci_start_signal_voltage_switch() for the normal
case e.g.

static int sdhci_am654_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 sdhci_am654_data *sdhci_am654 = sdhci_pltfm_priv(pltfm_host);


	if ((sdhci_am654->quirks & SDHCI_AM654_QUIRK_SUPPRESS_V1P8_ENA) &&
	    ios->signal_voltage == MMC_SIGNAL_VOLTAGE_180) {
		ret = mmc_regulator_set_vqmmc(mmc, ios);
		if (ret < 0) {
			pr_warn("%s: Switching to 1.8V signalling voltage failed\n",
				mmc_hostname(mmc));
			return -EIO;
		}
		return 0;
	}

	return sdhci_start_signal_voltage_switch(mmc, ios);
}

> +{
> +	struct sdhci_host *host = mmc_priv(mmc);
> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +	struct sdhci_am654_data *sdhci_am654 = sdhci_pltfm_priv(pltfm_host);
> +	u16 ctrl;
> +	int ret;
> +
> +	if (host->version < SDHCI_SPEC_300)
> +		return 0;
> +
> +	switch (ios->signal_voltage) {
> +	case MMC_SIGNAL_VOLTAGE_330:
> +		if (!(host->flags & SDHCI_SIGNALING_330))
> +			return -EINVAL;
> +
> +		ctrl &= ~SDHCI_CTRL_VDD_180;
> +		sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
> +
> +		if (!IS_ERR(mmc->supply.vqmmc)) {
> +			ret = mmc_regulator_set_vqmmc(mmc, ios);
> +			if (ret < 0) {
> +				pr_warn("%s: Switching to 3.3V signalling voltage failed\n",
> +					mmc_hostname(mmc));
> +				return -EIO;
> +			}
> +		}
> +
> +		usleep_range(5000, 5500);
> +
> +		ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
> +		if (!(ctrl & SDHCI_CTRL_VDD_180))
> +			return 0;
> +
> +		pr_warn("%s: 3.3V regulator output did not become stable\n",
> +			mmc_hostname(mmc));
> +
> +		return -EAGAIN;
> +
> +	case MMC_SIGNAL_VOLTAGE_180:
> +		if (!(host->flags & SDHCI_SIGNALING_180))
> +			return -EINVAL;
> +
> +		if (!IS_ERR(mmc->supply.vqmmc)) {
> +			ret = mmc_regulator_set_vqmmc(mmc, ios);
> +			if (ret < 0) {
> +				pr_warn("%s: Switching to 1.8V signalling voltage failed\n",
> +					mmc_hostname(mmc));
> +				return -EIO;
> +			}
> +		}
> +
> +		if (sdhci_am654->quirks & SDHCI_AM654_QUIRK_SET_V1P8_ENA) {
> +			ctrl |= SDHCI_CTRL_VDD_180;
> +			sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
> +
> +			ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
> +			if (ctrl & SDHCI_CTRL_VDD_180)
> +				return 0;
> +
> +			pr_warn("%s: 1.8V regulator output did not become stable\n",
> +				mmc_hostname(mmc));
> +
> +			return -EAGAIN;
> +		}
> +		return 0;
> +
> +	default:
> +		return 0;
> +	}
> +}
> +
>  static u8 sdhci_am654_write_power_on(struct sdhci_host *host, u8 val, int reg)
>  {
>  	writeb(val, host->ioaddr + reg);
> @@ -801,6 +875,8 @@ static int sdhci_am654_get_of_property(struct platform_device *pdev,
>  					struct sdhci_am654_data *sdhci_am654)
>  {
>  	struct device *dev = &pdev->dev;
> +	struct device_node *np = dev->of_node;
> +	struct device_node *node;
>  	int drv_strength;
>  	int ret;
>  
> @@ -844,6 +920,15 @@ static int sdhci_am654_get_of_property(struct platform_device *pdev,
>  	if (device_property_read_bool(dev, "ti,fails-without-test-cd"))
>  		sdhci_am654->quirks |= SDHCI_AM654_QUIRK_FORCE_CDTEST;
>  
> +	node = of_parse_phandle(np, "vmmc-supply", 0);
> +
> +	if (node) {
> +		node = of_parse_phandle(np, "vqmmc-supply", 0);
> +
> +		if (!node)
> +			sdhci_am654->quirks |= SDHCI_AM654_QUIRK_SET_V1P8_ENA;
> +	}

It would be simpler without 'np' and 'node'.  Not sure
what the rule is meant to be, but it could be something like:

	if (of_parse_phandle(dev->of_node, "vmmc-supply", 0) &&
	    of_parse_phandle(dev->of_node, "vqmmc-supply", 0)
		sdhci_am654->quirks |= SDHCI_AM654_QUIRK_SUPPRESS_V1P8_ENA;

> +
>  	sdhci_get_of_property(pdev);
>  
>  	return 0;
> @@ -940,6 +1025,7 @@ static int sdhci_am654_probe(struct platform_device *pdev)
>  		goto err_pltfm_free;
>  	}
>  
> +	host->mmc_host_ops.start_signal_voltage_switch = sdhci_am654_start_signal_voltage_switch;
>  	host->mmc_host_ops.execute_tuning = sdhci_am654_execute_tuning;
>  
>  	pm_runtime_get_noresume(dev);
> 
> base-commit: cf6444ba528f043398b112ac36e041a4d8685cb1