linux-kernel - Re: [PATCH 01/17] mmc: host: omap_hsmmc: use devm_regulator_get

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Date:	Fri, 31 Jul 2015 20:59:58 +0530
From:	Kishon Vijay Abraham I <kishon@...com>
To:	Grygorii Strashko <grygorii.strashko@...com>, <tony@...mide.com>,
	<ulf.hansson@...aro.org>, <afenkart@...il.com>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-omap@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-mmc@...r.kernel.org>
CC:	<nsekhar@...com>, Roger Quadros <rogerq@...com>
Subject: Re: [PATCH 01/17] mmc: host: omap_hsmmc: use devm_regulator_get_optional()
 for vmmc

Hi Grygorii,

On Wednesday 29 July 2015 05:39 PM, Grygorii Strashko wrote:
> On 07/29/2015 02:09 PM, Kishon Vijay Abraham I wrote:
>> Since vmmc can be optional for some platforms, use
>> devm_regulator_get_optional() for vmmc. Now return error only
>> in the case of -EPROBE_DEFER and for all other cases set
>> host->vcc to NULL.
>>
>> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
>> ---
>>   drivers/mmc/host/omap_hsmmc.c |    8 +++++---
>>   1 file changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
>> index 4d12032..b673e59 100644
>> --- a/drivers/mmc/host/omap_hsmmc.c
>> +++ b/drivers/mmc/host/omap_hsmmc.c
>> @@ -344,11 +344,13 @@ static int omap_hsmmc_reg_get(struct omap_hsmmc_host *host)
>>   	struct regulator *reg;
>>   	int ocr_value = 0;
>>   
>> -	reg = devm_regulator_get(host->dev, "vmmc");
>> +	reg = devm_regulator_get_optional(host->dev, "vmmc");
>>   	if (IS_ERR(reg)) {
>> -		dev_err(host->dev, "unable to get vmmc regulator %ld\n",
>> +		if (PTR_ERR(reg) == -EPROBE_DEFER)
>> +			return -EPROBE_DEFER;
>> +		host->vcc = NULL;
>> +		dev_dbg(host->dev, "unable to get vmmc regulator %ld\n",
>>   			PTR_ERR(reg));
>> -		return PTR_ERR(reg);
> 
> I think, It could be unsafe to just drop this return.
> regulator_get_optional may return:
> 1 valid pointer on regulator : success;
> 2 ERR_PTR(-ENODEV)           : regulator is not assigned, can proceed.
> 3 ERR_PTR(-EPROBE_DEFER)     : regulator is assigned, but not ready yet, retry.
> 4 ERR_PTR(<other error codes>: regulator is assigned, but can't be retrieved, failure, can't proceed
> 
> So, It's allowed to continue with host->vcc = NULL; only in case [2], while
> in case [4] probe should fail.

You are right. Will fix it and resend the patch.

Thanks
Kishon
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