2022-08-22 07:34:02

by Philipp Zabel

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

Hi Brad,

On Sa, 2022-08-20 at 12:57 -0700, Brad Larson wrote:
[...]
> +static void sdhci_mmc_hw_reset(struct mmc_host *mmc)
> +{
> + 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");
> +
> + reset_control_assert(priv->rst_hw);
> + /* For eMMC, minimum is 1us but give it 9us for good measure */
> + udelay(9);

At a glance, this seems excessive. Is there a reason 9 us is better
than, say, 2 or 3?

[...]
> @@ -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");

This should be described in cdns,sdhci.yaml first.

regards
Philipp

2022-08-31 23:00:57

by Larson, Bradley

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

On 8/22/22 12:03 AM, Philipp Zabel wrote:
> Hi Brad,
>
> On Sa, 2022-08-20 at 12:57 -0700, Brad Larson wrote:
> [...]
>> +static void sdhci_mmc_hw_reset(struct mmc_host *mmc)
>> +{
>> + 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");
>> +
>> + reset_control_assert(priv->rst_hw);
>> + /* For eMMC, minimum is 1us but give it 9us for good measure */
>> + udelay(9);
> At a glance, this seems excessive. Is there a reason 9 us is better
> than, say, 2 or 3?

Yes, 3x the minimum should be fine. Changed to 3 usec.


> [...]
>> @@ -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");
> This should be described in cdns,sdhci.yaml first.

Adding this to cdns,sdhci.yaml and running through schema checker.

--- a/Documentation/devicetree/bindings/mmc/cdns,sdhci.yaml
+++ b/Documentation/devicetree/bindings/mmc/cdns,sdhci.yaml
@@ -114,6 +114,16 @@ properties:
     minimum: 0
     maximum: 0x7f

+  reset-names:
+    items:
+      - const: hw
+
+  resets:
+    description:
+      optional. phandle to the system reset controller with line index
+      for mmc hw reset line if exists.
+    maxItems: 1
+
 required:
   - compatible


Regards,
Brad