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

Larson, Bradley
2022-08-31T23:29:48Z

On 8/22/22 3:53 AM, Ulf Hansson wrote:
> 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".

Changing 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?

Changing to 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?

Yes I think so and I'll be looking for guidance on this.

Regards,
Brad