linux-kernel - Re: [PATCH V1 1/3] mmc: sdhci: Allow platform controlled voltage switching

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Date:   Wed, 25 Jul 2018 17:53:52 +0530
From:   Vijay Viswanath <vviswana@...eaurora.org>
To:     Adrian Hunter <adrian.hunter@...el.com>, ulf.hansson@...aro.org,
        robh+dt@...nel.org, mark.rutland@....com
Cc:     linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        shawn.lin@...k-chips.com, linux-arm-msm@...r.kernel.org,
        georgi.djakov@...aro.org, devicetree@...r.kernel.org,
        asutoshd@...eaurora.org, stummala@...eaurora.org,
        venkatg@...eaurora.org, jeremymc@...hat.com,
        bjorn.andersson@...aro.org, riteshh@...eaurora.org,
        vbadigan@...eaurora.org, evgreen@...omium.org, dianders@...gle.com,
        sayalil@...eaurora.org, rampraka@...eaurora.org
Subject: Re: [PATCH V1 1/3] mmc: sdhci: Allow platform controlled voltage
 switching

Hi Adrian,


On 7/25/2018 5:23 PM, Adrian Hunter wrote:
> On 20/07/18 13:46, Vijay Viswanath wrote:
>> Some controllers can have internal mechanism to inform the SW that it
>> is ready for voltage switching. For such controllers, changing voltage
>> before the HW is ready can result in various issues.
>>
>> During setup/cleanup of host, check whether regulator enable/disable
>> was already done by platform driver.
>>
>> Signed-off-by: Vijay Viswanath <vviswana@...eaurora.org>
>> ---
>>   drivers/mmc/host/sdhci.c | 21 ++++++++++++++++-----
>>   1 file changed, 16 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>> index 1c828e0..494a1e2 100644
>> --- a/drivers/mmc/host/sdhci.c
>> +++ b/drivers/mmc/host/sdhci.c
>> @@ -3472,6 +3472,7 @@ int sdhci_setup_host(struct sdhci_host *host)
>>   	unsigned int override_timeout_clk;
>>   	u32 max_clk;
>>   	int ret;
>> +	bool enable_vqmmc = false;
>>   
>>   	WARN_ON(host == NULL);
>>   	if (host == NULL)
>> @@ -3485,7 +3486,12 @@ int sdhci_setup_host(struct sdhci_host *host)
>>   	 * the host can take the appropriate action if regulators are not
>>   	 * available.
>>   	 */
>> -	ret = mmc_regulator_get_supply(mmc);
>> +	if (!mmc->supply.vmmc) {
>> +		ret = mmc_regulator_get_supply(mmc);
>> +		enable_vqmmc  = true;
>> +	} else {
>> +		ret = 0;
>> +	}
>>   	if (ret)
>>   		return ret;
> 
> Why not
> 
> 	if (!mmc->supply.vmmc) {
> 		ret = mmc_regulator_get_supply(mmc);
> 	  	if (ret)
>    			return ret;
> 		enable_vqmmc  = true;
> 	}
> 

looks neater. Will do.

>>   
>> @@ -3736,7 +3742,10 @@ int sdhci_setup_host(struct sdhci_host *host)
>>   
>>   	/* If vqmmc regulator and no 1.8V signalling, then there's no UHS */
>>   	if (!IS_ERR(mmc->supply.vqmmc)) {
>> -		ret = regulator_enable(mmc->supply.vqmmc);
>> +		if (enable_vqmmc)
>> +			ret = regulator_enable(mmc->supply.vqmmc);
> 
> Please introduce host->vqmmc_enabled = !ret;
> 

Any reason to introduce vqmmc_enabled variable in sdhci_host structure ? 
We can get around with a local variable and using regulator_is_enabled API.

>> +		else
>> +			ret = 0;
>>   		if (!regulator_is_supported_voltage(mmc->supply.vqmmc, 1700000,
>>   						    1950000))
>>   			host->caps1 &= ~(SDHCI_SUPPORT_SDR104 |
>> @@ -3984,7 +3993,7 @@ int sdhci_setup_host(struct sdhci_host *host)
>>   	return 0;
>>   
>>   unreg:
>> -	if (!IS_ERR(mmc->supply.vqmmc))
>> +	if (!IS_ERR(mmc->supply.vqmmc) && enable_vqmmc)
> 
> And just make this
> 
> 	if (host->vqmmc_enabled)
> 
>>   		regulator_disable(mmc->supply.vqmmc);
>>   undma:
>>   	if (host->align_buffer)
>> @@ -4002,7 +4011,8 @@ void sdhci_cleanup_host(struct sdhci_host *host)
>>   {
>>   	struct mmc_host *mmc = host->mmc;
>>   
>> -	if (!IS_ERR(mmc->supply.vqmmc))
>> +	if (!IS_ERR(mmc->supply.vqmmc) &&
>> +			(regulator_is_enabled(mmc->supply.vqmmc) > 0))
> 
> 	if (host->vqmmc_enabled)
> 
>>   		regulator_disable(mmc->supply.vqmmc);
>>   
>>   	if (host->align_buffer)
>> @@ -4135,7 +4145,8 @@ void sdhci_remove_host(struct sdhci_host *host, int dead)
>>   
>>   	tasklet_kill(&host->finish_tasklet);
>>   
>> -	if (!IS_ERR(mmc->supply.vqmmc))
>> +	if (!IS_ERR(mmc->supply.vqmmc) &&
>> +			(regulator_is_enabled(mmc->supply.vqmmc) > 0))
> 
> 	if (host->vqmmc_enabled)
> 
>>   		regulator_disable(mmc->supply.vqmmc);
>>   
>>   	if (host->align_buffer)
>>
> 
> --
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> 

Thanks,
Vijay