[PATCH] mmc: change mmc_gpio_get_cd to call non-sleep gpio

[PATCH] mmc: change mmc_gpio_get_cd to call non-sleep gpio

[Christian Daudt]

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@broadcom.com>

diff --git a/drivers/mmc/core/slot-gpio.c b/drivers/mmc/core/slot-gpio.c
index 3242351..897b298 100644
--- a/drivers/mmc/core/slot-gpio.c
+++ b/drivers/mmc/core/slot-gpio.c
@@ -87,7 +87,7 @@ int mmc_gpio_get_cd(struct mmc_host *host)
 	if (!ctx || !gpio_is_valid(ctx->cd_gpio))
 		return -ENOSYS;
 
-	return !gpio_get_value_cansleep(ctx->cd_gpio) ^
+	return !gpio_get_value(ctx->cd_gpio) ^
 		!!(host->caps2 & MMC_CAP2_CD_ACTIVE_HIGH);
 }
 EXPORT_SYMBOL(mmc_gpio_get_cd);
-- 
1.7.10.4

Re: [PATCH] mmc: change mmc_gpio_get_cd to call non-sleep gpio

[Guennadi Liakhovetski]

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@broadcom.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.

Thanks
Guennadi

> 
> diff --git a/drivers/mmc/core/slot-gpio.c b/drivers/mmc/core/slot-gpio.c
> index 3242351..897b298 100644
> --- a/drivers/mmc/core/slot-gpio.c
> +++ b/drivers/mmc/core/slot-gpio.c
> @@ -87,7 +87,7 @@ int mmc_gpio_get_cd(struct mmc_host *host)
>  	if (!ctx || !gpio_is_valid(ctx->cd_gpio))
>  		return -ENOSYS;
>  
> -	return !gpio_get_value_cansleep(ctx->cd_gpio) ^
> +	return !gpio_get_value(ctx->cd_gpio) ^
>  		!!(host->caps2 & MMC_CAP2_CD_ACTIVE_HIGH);
>  }
>  EXPORT_SYMBOL(mmc_gpio_get_cd);
> -- 
> 1.7.10.4
> 
> 
> --
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> 

---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/

Re: [PATCH] mmc: change mmc_gpio_get_cd to call non-sleep gpio

[Christian Daudt]

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@broadcom.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

Re: [PATCH] mmc: change mmc_gpio_get_cd to call non-sleep gpio

[Christian Daudt]

On 13-08-08 02:10 PM, Christian Daudt wrote:
> 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@broadcom.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
>
[adding arm@kernel.org for more input]
Guennadi,
  While I can't see card-detect coming in through i2c gpio controller, I 
think that moving this out of the sleeping context (and into mmc_rescan) 
is probably the better solution anyways. So I'll drop this patch and 
send another one with that change instead.


  Thanks,
    csd