Re: [PATCH v10 14/15] mmc: sdhci-cadence: Support mmc hardware reset

[Adrian Hunter]

On 6/03/23 06:07, Brad Larson wrote:
> Add support for mmc hardware reset using a reset-controller
> that would need to be enabled in the device tree with
> a supporting driver.  The default is disabled for all
> existing designs.
> 
> Signed-off-by: Brad Larson <blarson@xxxxxxx>

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

> ---
> 
> v9 changes:
> - Previously patch 17/17
> - Changed delay after reset_control_assert() from 9 to 3 usec
> - Renamed sdhci_mmc_hw_reset() to sdhci_cdns_mmc_hw_reset()
> 
> ---
>  drivers/mmc/host/sdhci-cadence.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-cadence.c b/drivers/mmc/host/sdhci-cadence.c
> index 31c77d32aa7d..d13081da5e30 100644
> --- a/drivers/mmc/host/sdhci-cadence.c
> +++ b/drivers/mmc/host/sdhci-cadence.c
> @@ -12,6 +12,7 @@
>  #include <linux/mmc/mmc.h>
>  #include <linux/of.h>
>  #include <linux/of_device.h>
> +#include <linux/reset.h>
>  
>  #include "sdhci-pltfm.h"
>  
> @@ -70,6 +71,7 @@ struct sdhci_cdns_priv {
>  	spinlock_t wrlock;	/* write lock */
>  	bool enhanced_strobe;
>  	void (*priv_writel)(struct sdhci_cdns_priv *priv, u32 val, void __iomem *reg);
> +	struct reset_control *rst_hw;
>  	unsigned int nr_phy_params;
>  	struct sdhci_cdns_phy_param phy_params[];
>  };
> @@ -460,6 +462,22 @@ static void sdhci_cdns_hs400_enhanced_strobe(struct mmc_host *mmc,
>  					 SDHCI_CDNS_HRS06_MODE_MMC_HS400);
>  }
>  
> +static void sdhci_cdns_mmc_hw_reset(struct mmc_host *mmc)
> +{
> +	struct sdhci_host *host = mmc_priv(mmc);
> +	struct sdhci_cdns_priv *priv = sdhci_cdns_priv(host);
> +
> +	dev_dbg(mmc_dev(host->mmc), "emmc hardware reset\n");
> +
> +	reset_control_assert(priv->rst_hw);
> +	/* For eMMC, minimum is 1us but give it 3us for good measure */
> +	udelay(3);
> +
> +	reset_control_deassert(priv->rst_hw);
> +	/* For eMMC, minimum is 200us but give it 300us for good measure */
> +	usleep_range(300, 1000);
> +}
> +
>  static int sdhci_cdns_probe(struct platform_device *pdev)
>  {
>  	struct sdhci_host *host;
> @@ -523,6 +541,15 @@ static int sdhci_cdns_probe(struct platform_device *pdev)
>  	if (ret)
>  		goto free;
>  
> +	if (host->mmc->caps & MMC_CAP_HW_RESET) {
> +		priv->rst_hw = devm_reset_control_get_optional_exclusive(dev, "hw");
> +		if (IS_ERR(priv->rst_hw))
> +			return dev_err_probe(mmc_dev(host->mmc), PTR_ERR(priv->rst_hw),
> +					     "reset controller error\n");
> +		if (priv->rst_hw)
> +			host->mmc_host_ops.card_hw_reset = sdhci_cdns_mmc_hw_reset;
> +	}
> +
>  	ret = sdhci_add_host(host);
>  	if (ret)
>  		goto free;