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

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 22 March 2013 09:35, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
> On 22 March 2013 08:42, Huang Changming-R66093 <r66093@xxxxxxxxxxxxx> wrote:
>>
>> <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.
>> [jerry]
>> Not all Soc has GPIO to do this. our controller has the pin to detect the card status, need the external hardware to support it.
>> But due to some reasons, some boards don't do this work, so need the poll mode for all boards.
>>
>>> >> >> 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.
>>> >
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
>>> the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at
>>> http://vger.kernel.org/majordomo-info.html
>>
>>
>
> A suggestion; the poll time out is 1s today. We could make some more
> intelligent update to the timeout value so we decrease the number of
> timeouts to happen. In other words minimize the number of mmc_rescan
> to be executed.
>
> 1. When no card is inserted, use 1 s.
> 2. When card is inserted, switch to 30 s timeout. The card removal
> will be detected anyway when a blk err occurs, due to that
> mmc_detect_card_removed will be called from the block layer at error
> handling path.
>
> Any thoughts?

Well, one more thing is needed. MMC_CAP2_DETECT_ON_ERR shall be
removed and replaced with MMC_CAP_NEEDS_POLL in the
mmc_detect_card_removed function.

>
> Kind regards
> Ulf Hansson
--
To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[Index of Archives]     [Linux USB Devel]     [Linux Media]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux