linux-kernel - Re: [PATCH] mmc: change mmc_gpio_get

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Date:	Thu, 8 Aug 2013 14:10:58 -0700
From:	"Christian Daudt" <csd@...adcom.com>
To:	"Guennadi Liakhovetski" <g.liakhovetski@....de>
cc:	"Chris Ball" <cjb@...top.org>, "Shawn Guo" <shawn.guo@...aro.org>,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mmc: change mmc_gpio_get_cd to call non-sleep gpio

On 13-08-08 02:06 PM, Guennadi Liakhovetski wrote:
> On Thu, 8 Aug 2013, Christian Daudt wrote:
>
>> Given that mmc_gpio_get_cd can be called in softirq
>> context (by sdhci_tasklet_card -> sdhci_card_event ->
>> sdhci_do_get_cd -> mmc_gpio_get_cd ), it is necessary
>> for it to use gpio_get_value instead of
>> gpio_get_value_cansleep
>> Note that at present sdhci_card_event gets called both
>> from mmc_gpio_cd_irqt and sdhci_tasklet_card, and from
>> both it gets called immediately while the actual cd
>> processing is debounced to 200ms later. I think that
>> the better solution might be to move the sdhci_card_event
>> callback into mmc_rescan and remove it from its 2
>> present locations. That way the cd related callbacks
>> are aligned with the actual cd detection code. I can
>> submit a follow-up patch with these mods if that sounds
>> like a better way to solve this.
>>
>> Signed-off-by: Christian Daudt <csd@...adcom.com>
> I don't think this is a right approach. It will Oops if the card-detect
> GPIO is provided by, e.g. an I2C GPIO controller. Instead the driver
> should be fixed to only call this function from a sleeping context.
I don't think that card-detect would ever be tied to i2c but I might be 
wrong on that one... If there's agreement that moving sdhci_card_event 
into just being called from mmc_rescan is the better way to solve this, 
then I'll drop this patch and replace it with one that does just that.

  Thanks,
    csd


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