linux-kernel - Re: [PATCH V2] MMC: PM: add suspend/resume in atmel-mci

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Message-ID: <4E0DD816.7070104@atmel.com>
Date:	Fri, 01 Jul 2011 16:22:14 +0200
From:	Nicolas Ferre <nicolas.ferre@...el.com>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
CC:	cjb@...top.org, linux-mmc@...r.kernel.org,
	hans-christian.egtvedt@...el.com, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, kernel@...32linux.org
Subject: Re: [PATCH V2] MMC: PM: add suspend/resume in atmel-mci

Le 30/06/2011 15:13, Uwe Kleine-König :
> Hello Nicolas,
> 
> On Thu, Jun 30, 2011 at 03:49:41PM +0200, Nicolas Ferre wrote:
>> Take care of slots while going to suspend state.
>>
>> Signed-off-by: Nicolas Ferre <nicolas.ferre@...el.com>
>> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
>> ---
>> V2: move to pm_ops
>>
>>  drivers/mmc/host/atmel-mci.c |   47 ++++++++++++++++++++++++++++++++++++++++++
>>  1 files changed, 47 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/mmc/host/atmel-mci.c b/drivers/mmc/host/atmel-mci.c
>> index aa8039f..058f1842 100644
>> --- a/drivers/mmc/host/atmel-mci.c
>> +++ b/drivers/mmc/host/atmel-mci.c
>> @@ -1878,10 +1878,57 @@ static int __exit atmci_remove(struct platform_device *pdev)
>>  	return 0;
>>  }
>>  
>> +#ifdef CONFIG_PM
>> +static int atmci_suspend(struct device *dev)
>> +{
>> +	struct atmel_mci *host = dev_get_drvdata(dev);
>> +	struct atmel_mci_slot *slot;
>> +	int i, ret;
> slot and ret can have a more local scope.

ok.

>> +
>> +	 for (i = 0; i < ATMEL_MCI_MAX_NR_SLOTS; i++) {
>> +		slot = host->slot[i];
>> +		if (!slot)
>> +			continue;
>> +		ret = mmc_suspend_host(slot->mmc);
>> +		if (ret < 0) {
>> +			while (--i >= 0) {
>> +				slot = host->slot[i];
>> +				if (slot)
>> +					mmc_resume_host(host->slot[i]->mmc);
> hmm, mmc_resume_host could fail. But probably you cannot handle that in
> a sane way, do you?

Well, actually for the current implementation the only return code is... 0.
And here I try to have a king of best effort approach ;-)

>> +			}
>> +			return ret;
>> +		}
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static int atmci_resume(struct device *dev)
>> +{
>> +	struct atmel_mci *host = dev_get_drvdata(dev);
>> +	struct atmel_mci_slot *slot;
>> +	int i, ret;
>> +
>> +	for (i = 0; i < ATMEL_MCI_MAX_NR_SLOTS; i++) {
>> +		slot = host->slot[i];
>> +		if (!slot)
>> +			continue;
>> +		ret = mmc_resume_host(slot->mmc);
>> +		if (ret < 0)
>> +			return ret;
> Maybe you should try to resume host 5 even if resuming host 4 failed?

In fact all other drivers that are dealing with multiple slots are doing
the same... So I have difficulties to know the truth.
The question is: is it better to return an error to the "resume"
function so that we are called later again or do we have to do our best
to thaw everything out?

>> +	}
>> +
>> +	return 0;
>> +}
>> +#endif
>> +static SIMPLE_DEV_PM_OPS(atmci_pm, atmci_suspend, atmci_resume);
>> +
>> +
> For my taste a single empty line is enough.

Ok.

>>  static struct platform_driver atmci_driver = {
>>  	.remove		= __exit_p(atmci_remove),
>>  	.driver		= {
>>  		.name		= "atmel_mci",
>> +		.pm		= &atmci_pm,
>>  	},
>>  };
> 

Thanks, best regards,
-- 
Nicolas Ferre

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