[PATCH v7 1/2] mmc: core: enhance card removal judgement for slow removal

[PATCH v7 1/2] mmc: core: enhance card removal judgement for slow removal

[Kevin Liu]

Function _mmc_detect_card_removed will be called to know whether
the card is still present when host->bus_ops->detect is called.
In current code, the return value of this function generally only
depend on the result of sending cmd13 to card, which may not safe
for card with detection support like slot gpio detection.
Because the communication status between host and card may out of
sync with the detect status if remove the card slowly or hands shake
during the process. The direct reason is the async between card
detect switch and card/slot pad contaction in hardware, which is
defined by spec.

The spec define card insert/remove sequence as below (both standard size
SD card and MicroSD card have the same sequence):
"Part 1 Standard Size SD Card Mechanical Addendum Ver4.00 Final,
Appendix C: Card Detection Switch" (Take normally open type as example)
a)SD card insertion sequence:
  The card detection switch should be turned on after all SD card
  contact pads are connected to the host connector contact pads.
b)SD removal sequence:
  The card detection switch should be turned off when the SD card
  is just going to be removed and before any SD card contact pad is
  disconnected from the host connector contact pad.

Below is the sequence when this issue occur (Take slot gpio detection
as example and remove the card slowly during the process):
1. gpio level changed and card detect interrupt triggered.
2. mmc_rescan was launched.
3. the card pads were still contacted with the slot pads because of slow
   removal. So _mmc_detect_card_removed and mmc_rescan think card was
   still present (cmd13 succeed).
4. card pads were discontacted from the card slot pads.
So the card was actually removed finally but the card removal event
has been missed by system.
The interval length between step 1 and step 4 depends on the
card removal speed. If it's longer than the detect work schedule
delay which is 200ms, this issue will likely happen.

This patch add the card detect status check in function
_mmc_detect_card_removed if cmd13 check succeed and host->ops->get_cd
provided. If get_cd detect no card present then schedule another detect
work 200ms later.

Signed-off-by: Kevin Liu <kliu5@marvell.com>
---
 drivers/mmc/core/core.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index b8c3d41..d9ac96c 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -2290,6 +2290,19 @@ int _mmc_detect_card_removed(struct mmc_host *host)
 		return 1;
 
 	ret = host->bus_ops->alive(host);
+	/*
+	 * Card detect status and alive check may out of sync if card is
+	 * removed slowly when card detect switch changed while card/slot
+	 * pads still contacted in hardware.(refer to "SD Card Mechanical
+	 * Addendum, Appendix C: Card Detection Switch") So reschedule a
+	 * detect work 200ms later for this case.
+	 */
+	if (!ret && host->ops->get_cd && !host->ops->get_cd(host)) {
+		mmc_detect_change(host, msecs_to_jiffies(200));
+		pr_debug("%s: card remove too slowly\n",
+				mmc_hostname(host));
+	}
+
 	if (ret) {
 		mmc_card_set_removed(host->card);
 		pr_debug("%s: card remove detected\n", mmc_hostname(host));
-- 
1.7.9.5

Re: [PATCH v7 1/2] mmc: core: enhance card removal judgement for slow removal

[Ulf Hansson]

On 28 February 2013 08:29, Kevin Liu <kliu5@marvell.com> wrote:
> Function _mmc_detect_card_removed will be called to know whether
> the card is still present when host->bus_ops->detect is called.
> In current code, the return value of this function generally only
> depend on the result of sending cmd13 to card, which may not safe
> for card with detection support like slot gpio detection.
> Because the communication status between host and card may out of
> sync with the detect status if remove the card slowly or hands shake
> during the process. The direct reason is the async between card
> detect switch and card/slot pad contaction in hardware, which is
> defined by spec.
>
> The spec define card insert/remove sequence as below (both standard size
> SD card and MicroSD card have the same sequence):
> "Part 1 Standard Size SD Card Mechanical Addendum Ver4.00 Final,
> Appendix C: Card Detection Switch" (Take normally open type as example)
> a)SD card insertion sequence:
>   The card detection switch should be turned on after all SD card
>   contact pads are connected to the host connector contact pads.
> b)SD removal sequence:
>   The card detection switch should be turned off when the SD card
>   is just going to be removed and before any SD card contact pad is
>   disconnected from the host connector contact pad.
>
> Below is the sequence when this issue occur (Take slot gpio detection
> as example and remove the card slowly during the process):
> 1. gpio level changed and card detect interrupt triggered.
> 2. mmc_rescan was launched.
> 3. the card pads were still contacted with the slot pads because of slow
>    removal. So _mmc_detect_card_removed and mmc_rescan think card was
>    still present (cmd13 succeed).
> 4. card pads were discontacted from the card slot pads.
> So the card was actually removed finally but the card removal event
> has been missed by system.
> The interval length between step 1 and step 4 depends on the
> card removal speed. If it's longer than the detect work schedule
> delay which is 200ms, this issue will likely happen.
>
> This patch add the card detect status check in function
> _mmc_detect_card_removed if cmd13 check succeed and host->ops->get_cd
> provided. If get_cd detect no card present then schedule another detect
> work 200ms later.
>
> Signed-off-by: Kevin Liu <kliu5@marvell.com>
> ---
>  drivers/mmc/core/core.c |   13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index b8c3d41..d9ac96c 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -2290,6 +2290,19 @@ int _mmc_detect_card_removed(struct mmc_host *host)
>                 return 1;
>
>         ret = host->bus_ops->alive(host);
> +       /*
> +        * Card detect status and alive check may out of sync if card is
> +        * removed slowly when card detect switch changed while card/slot
> +        * pads still contacted in hardware.(refer to "SD Card Mechanical
> +        * Addendum, Appendix C: Card Detection Switch") So reschedule a
> +        * detect work 200ms later for this case.
> +        */
> +       if (!ret && host->ops->get_cd && !host->ops->get_cd(host)) {
> +               mmc_detect_change(host, msecs_to_jiffies(200));
> +               pr_debug("%s: card remove too slowly\n",
> +                               mmc_hostname(host));
> +       }
> +
>         if (ret) {
>                 mmc_card_set_removed(host->card);
>                 pr_debug("%s: card remove detected\n", mmc_hostname(host));
> --
> 1.7.9.5
>

Great work Kevin and thanks for convincing me around this patch! :-)

I also intend to remove the MMC_CAP2_DETECT_ON_ERR code, I don't see a
need for it anymore.

Acked-by: Ulf Hansson <ulf.hansson@linaro.org>

Re: [PATCH v7 1/2] mmc: core: enhance card removal judgement for slow removal

[Johan Rudholm]

Hi,

2013/2/28 Ulf Hansson <ulf.hansson@linaro.org>:
> On 28 February 2013 08:29, Kevin Liu <kliu5@marvell.com> wrote:
>> Function _mmc_detect_card_removed will be called to know whether
>> the card is still present when host->bus_ops->detect is called.
>> In current code, the return value of this function generally only
>> depend on the result of sending cmd13 to card, which may not safe
>> for card with detection support like slot gpio detection.
>> Because the communication status between host and card may out of
>> sync with the detect status if remove the card slowly or hands shake
>> during the process. The direct reason is the async between card
>> detect switch and card/slot pad contaction in hardware, which is
>> defined by spec.
>>
>> The spec define card insert/remove sequence as below (both standard size
>> SD card and MicroSD card have the same sequence):
>> "Part 1 Standard Size SD Card Mechanical Addendum Ver4.00 Final,
>> Appendix C: Card Detection Switch" (Take normally open type as example)
>> a)SD card insertion sequence:
>>   The card detection switch should be turned on after all SD card
>>   contact pads are connected to the host connector contact pads.
>> b)SD removal sequence:
>>   The card detection switch should be turned off when the SD card
>>   is just going to be removed and before any SD card contact pad is
>>   disconnected from the host connector contact pad.
>>
>> Below is the sequence when this issue occur (Take slot gpio detection
>> as example and remove the card slowly during the process):
>> 1. gpio level changed and card detect interrupt triggered.
>> 2. mmc_rescan was launched.
>> 3. the card pads were still contacted with the slot pads because of slow
>>    removal. So _mmc_detect_card_removed and mmc_rescan think card was
>>    still present (cmd13 succeed).
>> 4. card pads were discontacted from the card slot pads.
>> So the card was actually removed finally but the card removal event
>> has been missed by system.
>> The interval length between step 1 and step 4 depends on the
>> card removal speed. If it's longer than the detect work schedule
>> delay which is 200ms, this issue will likely happen.
>>
>> This patch add the card detect status check in function
>> _mmc_detect_card_removed if cmd13 check succeed and host->ops->get_cd
>> provided. If get_cd detect no card present then schedule another detect
>> work 200ms later.
>>
>> Signed-off-by: Kevin Liu <kliu5@marvell.com>
>> ---
>>  drivers/mmc/core/core.c |   13 +++++++++++++
>>  1 file changed, 13 insertions(+)
>>
>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
>> index b8c3d41..d9ac96c 100644
>> --- a/drivers/mmc/core/core.c
>> +++ b/drivers/mmc/core/core.c
>> @@ -2290,6 +2290,19 @@ int _mmc_detect_card_removed(struct mmc_host *host)
>>                 return 1;
>>
>>         ret = host->bus_ops->alive(host);
>> +       /*
>> +        * Card detect status and alive check may out of sync if card is
>> +        * removed slowly when card detect switch changed while card/slot
>> +        * pads still contacted in hardware.(refer to "SD Card Mechanical
>> +        * Addendum, Appendix C: Card Detection Switch") So reschedule a
>> +        * detect work 200ms later for this case.
>> +        */
>> +       if (!ret && host->ops->get_cd && !host->ops->get_cd(host)) {
>> +               mmc_detect_change(host, msecs_to_jiffies(200));
>> +               pr_debug("%s: card remove too slowly\n",
>> +                               mmc_hostname(host));
>> +       }
>> +
>>         if (ret) {
>>                 mmc_card_set_removed(host->card);
>>                 pr_debug("%s: card remove detected\n", mmc_hostname(host));
>> --
>> 1.7.9.5
>>
>
> Great work Kevin and thanks for convincing me around this patch! :-)
>
> I also intend to remove the MMC_CAP2_DETECT_ON_ERR code, I don't see a
> need for it anymore.
>
> Acked-by: Ulf Hansson <ulf.hansson@linaro.org>

and

Tested-by: Johan Rudholm <johan.rudholm@stericsson.com>

//Johan

Re: [PATCH v7 1/2] mmc: core: enhance card removal judgement for slow removal

[Philip Rakity]

Reviewed-by: Philip Rakity <prakity@nvidia.com>

On Feb 28, 2013, at 7:29 AM, Kevin Liu <kliu5@marvell.com> wrote:

> Function _mmc_detect_card_removed will be called to know whether
> the card is still present when host->bus_ops->detect is called.
> In current code, the return value of this function generally only
> depend on the result of sending cmd13 to card, which may not safe
> for card with detection support like slot gpio detection.
> Because the communication status between host and card may out of
> sync with the detect status if remove the card slowly or hands shake
> during the process. The direct reason is the async between card
> detect switch and card/slot pad contaction in hardware, which is
> defined by spec.
> 
> The spec define card insert/remove sequence as below (both standard size
> SD card and MicroSD card have the same sequence):
> "Part 1 Standard Size SD Card Mechanical Addendum Ver4.00 Final,
> Appendix C: Card Detection Switch" (Take normally open type as example)
> a)SD card insertion sequence:
>  The card detection switch should be turned on after all SD card
>  contact pads are connected to the host connector contact pads.
> b)SD removal sequence:
>  The card detection switch should be turned off when the SD card
>  is just going to be removed and before any SD card contact pad is
>  disconnected from the host connector contact pad.
> 
> Below is the sequence when this issue occur (Take slot gpio detection
> as example and remove the card slowly during the process):
> 1. gpio level changed and card detect interrupt triggered.
> 2. mmc_rescan was launched.
> 3. the card pads were still contacted with the slot pads because of slow
>   removal. So _mmc_detect_card_removed and mmc_rescan think card was
>   still present (cmd13 succeed).
> 4. card pads were discontacted from the card slot pads.
> So the card was actually removed finally but the card removal event
> has been missed by system.
> The interval length between step 1 and step 4 depends on the
> card removal speed. If it's longer than the detect work schedule
> delay which is 200ms, this issue will likely happen.
> 
> This patch add the card detect status check in function
> _mmc_detect_card_removed if cmd13 check succeed and host->ops->get_cd
> provided. If get_cd detect no card present then schedule another detect
> work 200ms later.
> 
> Signed-off-by: Kevin Liu <kliu5@marvell.com>
> ---
> drivers/mmc/core/core.c |   13 +++++++++++++
> 1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index b8c3d41..d9ac96c 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -2290,6 +2290,19 @@ int _mmc_detect_card_removed(struct mmc_host *host)
> 		return 1;
> 
> 	ret = host->bus_ops->alive(host);
> +	/*
> +	 * Card detect status and alive check may out of sync if card is
> +	 * removed slowly when card detect switch changed while card/slot
> +	 * pads still contacted in hardware.(refer to "SD Card Mechanical
> +	 * Addendum, Appendix C: Card Detection Switch") So reschedule a
> +	 * detect work 200ms later for this case.
> +	 */
> +	if (!ret && host->ops->get_cd && !host->ops->get_cd(host)) {
> +		mmc_detect_change(host, msecs_to_jiffies(200));
> +		pr_debug("%s: card remove too slowly\n",
> +				mmc_hostname(host));
> +	}
> +
> 	if (ret) {
> 		mmc_card_set_removed(host->card);
> 		pr_debug("%s: card remove detected\n", mmc_hostname(host));
> -- 
> 1.7.9.5
> 

Re: [PATCH v7 1/2] mmc: core: enhance card removal judgement for slow removal

[Chris Ball]

Hi,

On Thu, Feb 28 2013, Kevin Liu wrote:
> Function _mmc_detect_card_removed will be called to know whether
> the card is still present when host->bus_ops->detect is called.
> In current code, the return value of this function generally only
> depend on the result of sending cmd13 to card, which may not safe
> for card with detection support like slot gpio detection.
> Because the communication status between host and card may out of
> sync with the detect status if remove the card slowly or hands shake
> during the process. The direct reason is the async between card
> detect switch and card/slot pad contaction in hardware, which is
> defined by spec.
>
> The spec define card insert/remove sequence as below (both standard size
> SD card and MicroSD card have the same sequence):
> "Part 1 Standard Size SD Card Mechanical Addendum Ver4.00 Final,
> Appendix C: Card Detection Switch" (Take normally open type as example)
> a)SD card insertion sequence:
>   The card detection switch should be turned on after all SD card
>   contact pads are connected to the host connector contact pads.
> b)SD removal sequence:
>   The card detection switch should be turned off when the SD card
>   is just going to be removed and before any SD card contact pad is
>   disconnected from the host connector contact pad.
>
> Below is the sequence when this issue occur (Take slot gpio detection
> as example and remove the card slowly during the process):
> 1. gpio level changed and card detect interrupt triggered.
> 2. mmc_rescan was launched.
> 3. the card pads were still contacted with the slot pads because of slow
>    removal. So _mmc_detect_card_removed and mmc_rescan think card was
>    still present (cmd13 succeed).
> 4. card pads were discontacted from the card slot pads.
> So the card was actually removed finally but the card removal event
> has been missed by system.
> The interval length between step 1 and step 4 depends on the
> card removal speed. If it's longer than the detect work schedule
> delay which is 200ms, this issue will likely happen.
>
> This patch add the card detect status check in function
> _mmc_detect_card_removed if cmd13 check succeed and host->ops->get_cd
> provided. If get_cd detect no card present then schedule another detect
> work 200ms later.
>
> Signed-off-by: Kevin Liu <kliu5@marvell.com>

Thanks, pushed to mmc-next for 3.10.

- Chris.
-- 
Chris Ball   <cjb@laptop.org>   <http://printf.net/>
One Laptop Per Child