linux-kernel - Re: [PATCH v9 14/15] mmc: sdhci-cadence: Support mmc hardware reset

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Date:   Tue, 7 Feb 2023 12:53:21 -0800
From:   Brad Larson <blarson@....com>
To:     <p.zabel@...gutronix.de>
CC:     <adrian.hunter@...el.com>, <alcooperx@...il.com>,
        <andy.shevchenko@...il.com>, <arnd@...db.de>, <blarson@....com>,
        <brendan.higgins@...ux.dev>, <briannorris@...omium.org>,
        <brijeshkumar.singh@....com>, <broonie@...nel.org>,
        <catalin.marinas@....com>, <davidgow@...gle.com>,
        <devicetree@...r.kernel.org>, <fancer.lancer@...il.com>,
        <gerg@...ux-m68k.org>, <gsomlo@...il.com>, <krzk@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <lee.jones@...aro.org>,
        <lee@...nel.org>, <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-mmc@...r.kernel.org>,
        <linux-spi@...r.kernel.org>, <rdunlap@...radead.org>,
        <robh+dt@...nel.org>, <samuel@...lland.org>,
        <skhan@...uxfoundation.org>, <suravee.suthikulpanit@....com>,
        <thomas.lendacky@....com>, <tonyhuang.sunplus@...il.com>,
        <ulf.hansson@...aro.org>, <vaishnav.a@...com>, <will@...nel.org>,
        <yamada.masahiro@...ionext.com>
Subject: Re: [PATCH v9 14/15] mmc: sdhci-cadence: Support mmc hardware reset

Hi Philipp,

On Thu, Jan 19, 2023 at 10:34, Philipp Zabel wrote:
> On Wed, Jan 18, 2023 at 07:51:35PM -0800, 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@....com>
>> ---
>> 
>> Changes since v6:
>> - 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 | 31 +++++++++++++++++++++++++++++++
>>  1 file changed, 31 insertions(+)
>> 
>> diff --git a/drivers/mmc/host/sdhci-cadence.c b/drivers/mmc/host/sdhci-cadence.c
>> index e92aa79a8be2..62321cef41db 100644
>> --- a/drivers/mmc/host/sdhci-cadence.c
>> +++ b/drivers/mmc/host/sdhci-cadence.c
>> @@ -12,6 +12,7 @@
[...]
>>  static int sdhci_cdns_probe(struct platform_device *pdev)
>>  {
>>  	struct sdhci_host *host;
>> @@ -521,6 +541,17 @@ 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;
>
> The optional reset_control_get variants return NULL instead of -ENOENT
> if no reset is specified.
>
> This should return on any error instead.
>
>> +		} else {
>> +			host->mmc_host_ops.card_hw_reset = sdhci_cdns_mmc_hw_reset;
>
> This probably shouldn't be set if reset_control_get_optional returned NULL.
[...]

Thanks I see now with the argument optional=true in __of_reset_control_get() it is
returning NULL and not -ENOENT.  This is the updated version.

+       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;
+       }

Regards,
Brad