Re: [PATCH 1/3i v6] MMC/SD: Add callback function to detect card

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2013/3/22 Huang Changming-R66093 <r66093@xxxxxxxxxxxxx>:
>
>> -----Original Message-----
>> From: linux-mmc-owner@xxxxxxxxxxxxxxx [mailto:linux-mmc-
>> owner@xxxxxxxxxxxxxxx] On Behalf Of Kevin Liu
>> Sent: Friday, March 22, 2013 2:55 PM
>> To: Huang Changming-R66093
>> Cc: linux-mmc@xxxxxxxxxxxxxxx; Chris Ball; Ulf Hansson
>> Subject: Re: [PATCH 1/3i v6] MMC/SD: Add callback function to detect card
>>
>> 2013/3/22 Huang Changming-R66093 <r66093@xxxxxxxxxxxxx>:
>> >> Jerry,
>> >>
>> >> Function _mmc_detect_card_removed should only be called when card
>> >> insert/removal or i/o error occur unless POLLING is used(called once
>> >> per second). So it should _not_ impact performance much.
>> > [jerry]
>> > No, your understanding is wrong.
>> > Function "_mmc_detect_card_removed " is called to check if our card has
>> been removed when driver run the function "mmc_rescan" every time.
>> >
>>
>> But when will mmc_rescan be called?
>> Besides boot up, only when card status change it will be called.
>> So usually it should _not_ be called frequently.
> [jerry]
> For poll mode, how to know card status changed?
> The answer is "mmc_rescan".
> maybe you could read the last two lines of this function ago.
>

I mentioned this in my first response "unless POLLING is used(called once
per second)". I was a bit confused firstly.
I think slot-gpio is a better solution, with which you don't need the
every second polling.

>> >> POLLING is poor for performance, why not change to slot-gpio if host
>> >> is broken for card detect.
>> > [jerry]
>> > Some our boards can't support interrupt mode to detect card
>> insert/removable, so we unify the poll mode.
>> >
>>
>> Not support gpio interrupt?
>> I think you only don't support sdh host interrupt.
>
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