linux-kernel - Re: [PATCH] mmc: core: Wait for Vdd to settle on card power off

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Message-ID: <802daedb-d82c-4d0b-8e69-d166c169cbb1@intel.com>
Date: Thu, 13 Mar 2025 10:20:52 +0200
From: Adrian Hunter <adrian.hunter@...el.com>
To: Erick Shepherd <erick.shepherd@...com>
CC: <brad.mouring@...com>, <gratian.crisan@...rson.com>,
	<kyle.roeschley@...com>, <linux-kernel@...r.kernel.org>,
	<linux-mmc@...r.kernel.org>, <ulf.hansson@...aro.org>
Subject: Re: [PATCH] mmc: core: Wait for Vdd to settle on card power off

On 13/03/25 05:35, Erick Shepherd wrote:
>> What about something like this?
> 
>> diff --git a/drivers/mmc/host/sdhci-pci-core.c b/drivers/mmc/host/sdhci-pci-core.c
>> index 1f0bd723f011..0789df732e93 100644
>> --- a/drivers/mmc/host/sdhci-pci-core.c
>> +++ b/drivers/mmc/host/sdhci-pci-core.c
>> @@ -610,8 +610,11 @@ static void sdhci_intel_set_power(struct sdhci_host *host, unsigned char mode,
>  
>>  	sdhci_set_power(host, mode, vdd);
>  
>> -	if (mode == MMC_POWER_OFF)
>> +	if (mode == MMC_POWER_OFF) {
>> +		if (slot->chip->pdev->device == PCI_DEVICE_ID_INTEL_APL_SD)
>> +			usleep_range(15000, 17500);
>>  		return;
>> +	}
>  
>> 	/*
>> 	 * Bus power might not enable after D3 -> D0 transition due to the
> 
> I talked to one of our digital hardware engineers who worked on this
> issue. He believes that the issue is likely affecting more than just 
> Apollo Lake devices and recommended keeping the delay for all of our
> devices. Could something like this work?
> 
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -2176,6 +2176,9 @@ EXPORT_SYMBOL_GPL(sdhci_set_power_noreg);
>  void sdhci_set_power(struct sdhci_host *host, unsigned char mode,
>  		     unsigned short vdd)
>  {
> +	if (mode == MMC_POWER_OFF)
> +		usleep_range(15000, 17500);
> +
>  	if (IS_ERR(host->mmc->supply.vmmc))
>  		sdhci_set_power_noreg(host, mode, vdd);
>  	else

sdhci is used by a number of drivers (drivers/mmc/host/sdhci*)
that typically use the regulator framework to meet voltage
requirements. So that is not the right place to make changes.

It would be best to put the affected PCI device IDs into
sdhci_intel_set_power() as I showed.