On 09/01/12 13:02, Ulf Hansson wrote:
> Adrian Hunter wrote:
>> On 3/01/2012 12:33 p.m., Ulf Hansson wrote:
>>> Removing a card "slowly" can trigger a GPIO irq to be raised far
>>> before the card is actually removed. This means the scheduled
>>> detect work will not find out that the card were removed and thus
>>> the card and the block device will not be unregistered.
>>
>> One way around that problem is to error out requests after the GPIO
>> indicates the card is "removed". sdhci effectively does that but with
>> a "present" bit. Perhaps even simpler - set the card-removed flag.
>
> I get the idea, but that will only partly solve this issue.
>
> My concern is more about what we actually can trust; either the GPIO irq
> which likely is giving more than one irq when inserting/removing a card
> since the slot is probably not glitch free, or that a "rescan" runs to make
> sure a CMD13 is accepted from the previously inserted card.
Yes, I guess you would need to debounce the GPIO if you wanted to rely on it.
>
> Moreover, the issue this patch tries to solve can not be solved without
> doing a "rescan" which must be triggered from the the block layer some how.
> I thought this new function that you previously added
> "mmc_detect_card_remove" was the proper place to do this.
>
>>
>>> Let the mmc_detect_card_removed function trigger a new detect
>>> work immediately when it discovers that a card has been removed.
>>
>> This is changing some long-standing functionality i.e. the card is not
>> removed
>> without a card detect event. It is difficult to know whether that will be
>> very
>> bad for poor quality cards,
>
> Doing a mmc_detect (rescan) will in the end just issue a CMD13 to the card
> to make sure it is still present, that is already done from the block layer
> after each read/write request. So I can not see that "poor quality cards"
> will have any further problem with this patch, but I might miss something!?
The block driver has never caused a card to be removed before. That is new
and it is designed to preserve existing behaviour i.e. do not remove a card
without a card detect event.
You are assuming:
1. that a poor quality card will not return errors for a few
commands and then resume operation
2. that removing a card on error is desirable
Both those assumptions may be true, but there is no evidence that they are.
>
>>
>>> This will solve the described issue above. Moreover we make sure
>>> the detect work is executed as soon as possible, since there is
>>> no reason for waiting for a "delayed" detect to happen.
>>>
>>> Signed-off-by: Ulf Hansson<[email protected]>
>>> ---
>>> drivers/mmc/core/core.c | 24 +++++++++++++-----------
>>> include/linux/mmc/host.h | 1 -
>>> 2 files changed, 13 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
>>> index 4770807..7bc02f4 100644
>>> --- a/drivers/mmc/core/core.c
>>> +++ b/drivers/mmc/core/core.c
>>> @@ -1462,7 +1462,6 @@ void mmc_detect_change(struct mmc_host *host,
>>> unsigned long delay)
>>> WARN_ON(host->removed);
>>> spin_unlock_irqrestore(&host->lock, flags);
>>> #endif
>>> - host->detect_change = 1;
>>> mmc_schedule_delayed_work(&host->detect, delay);
>>> }
>>>
>>> @@ -2077,18 +2076,23 @@ int _mmc_detect_card_removed(struct mmc_host *host)
>>> int mmc_detect_card_removed(struct mmc_host *host)
>>> {
>>> struct mmc_card *card = host->card;
>>> + int ret = 1;
>>>
>>> WARN_ON(!host->claimed);
>>> - /*
>>> - * The card will be considered unchanged unless we have been asked to
>>> - * detect a change or host requires polling to provide card detection.
>>> - */
>>> - if (card&& !host->detect_change&& !(host->caps& MMC_CAP_NEEDS_POLL))
>>> - return mmc_card_removed(card);
>>>
>>> - host->detect_change = 0;
>>> + if (card&& !mmc_card_removed(card)) {
>>> + if (_mmc_detect_card_removed(host)) {
>>> + /*
>>> + * Make sure a detect work is always executed and also
>>> + * do it as soon as possible.
>>> + */
>>> + cancel_delayed_work(&host->detect);
>>> + mmc_detect_change(host, 0);
>>> + }
>>> + ret = mmc_card_removed(card);
>>> + }
>>>
>>> - return _mmc_detect_card_removed(host);
>>> + return ret;
>>> }
>>> EXPORT_SYMBOL(mmc_detect_card_removed);
>>>
>>> @@ -2112,8 +2116,6 @@ void mmc_rescan(struct work_struct *work)
>>> && !(host->caps& MMC_CAP_NONREMOVABLE))
>>> host->bus_ops->detect(host);
>>>
>>> - host->detect_change = 0;
>>> -
>>> /*
>>> * Let mmc_bus_put() free the bus/bus_ops if we've found that
>>> * the card is no longer present.
>>> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
>>> index 031d865..09fa5e6 100644
>>> --- a/include/linux/mmc/host.h
>>> +++ b/include/linux/mmc/host.h
>>> @@ -305,7 +305,6 @@ struct mmc_host {
>>> int claim_cnt; /* "claim" nesting count */
>>>
>>> struct delayed_work detect;
>>> - int detect_change; /* card detect flag */
>>> struct mmc_hotplug hotplug;
>>>
>>> const struct mmc_bus_ops *bus_ops; /* current bus driver */
>>
>>
>
> Br
> Ulf Hansson
>
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