Re: [PATCH v6 17/17] mmc: sdhci-cadence: Support mmc hardware reset

Ulf Hansson
2022-08-22T10:54:07Z

On Sat, 20 Aug 2022 at 21:58, Brad Larson <brad@pensando.io> wrote:
>
> From: Brad Larson <blarson@amd.com>
>
> Add support for mmc hardware reset with a reset-controller
> which 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@amd.com>
> ---
> drivers/mmc/host/sdhci-cadence.c | 29 +++++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci-cadence.c b/drivers/mmc/host/sdhci-cadence.c
> index c662c63d49fa..35d37b9aba63 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[];
> };
> @@ -458,6 +460,22 @@ static void sdhci_cdns_hs400_enhanced_strobe(struct mmc_host *mmc,
> SDHCI_CDNS_HRS06_MODE_MMC_HS400);
> }
>
> +static void sdhci_mmc_hw_reset(struct mmc_host *mmc)

Nitpick: Probably better to be consistent with the prefixes for
function names. So, I suggest changing this to
"sdhci_cdns_mmc_hw_reset".

> +{
> + struct sdhci_host *host = mmc_priv(mmc);
> + struct sdhci_cdns_priv *priv = sdhci_cdns_priv(host);
> +
> + dev_info(mmc_dev(host->mmc), "emmc hardware reset\n");

Maybe it's sufficient with dev_dbg?

> +
> + reset_control_assert(priv->rst_hw);
> + /* For eMMC, minimum is 1us but give it 9us for good measure */
> + udelay(9);
> +
> + 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;
> @@ -520,6 +538,17 @@ 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)) {
> + ret = PTR_ERR(priv->rst_hw);
> + if (ret == -ENOENT)
> + priv->rst_hw = NULL;
> + } else {
> + host->mmc_host_ops.card_hw_reset = sdhci_mmc_hw_reset;
> + }
> + }
> +
> ret = sdhci_add_host(host);
> if (ret)
> goto free;
> --

Other than the comments above, I wonder about what merging strategy we
should use for the series. I believe it looks fine for me to pick up
the mmc related patches, thus we can apply patches on a per subsystem
basis, right?

Kind regards
Uffe