On 22 March 2013 09:35, Ulf Hansson <ulf.hans...@linaro.org> wrote: > On 22 March 2013 08:42, Huang Changming-R66093 <r66...@freescale.com> wrote: >> >> <r66...@freescale.com>: >>> >> >> 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 majord...@vger.kernel.org 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 majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
