Thanks a lot, Johan. Best Regards Jerry Huang > -----Original Message----- > From: Johan Rudholm [mailto:jrudholm@xxxxxxxxx] > Sent: Monday, November 05, 2012 10:08 PM > To: Huang Changming-R66093 > Cc: linux-mmc@xxxxxxxxxxxxxxx; Anton Vorontsov; Chris Ball > Subject: Re: [PATCH 2/4 v4] MMC/SD: Add callback function to detect card > > Hi, > > 2012/11/5 Huang Changming-R66093 <r66093@xxxxxxxxxxxxx>: > >> > >> 2012/11/2 Huang Changming-R66093 <r66093@xxxxxxxxxxxxx>: > >> > Hi, Johan, > >> > When quicks SDHCI_QUIRK_BROKEN_CARD_DETECTION is set, the driver > will > >> poll the card status with the command CMD13 periodically, then many > >> interrupts will be generated, which affect the performance. > >> > >> Ok, just to see if I understand the scenario correctly: > >> SDHCI_QUIRK_BROKEN_CARD_DETECTION causes the MMC_CAP_NEEDS_POLL cap to > be > >> set, which will cause mmc_rescan to be run at a one second interval. > >> mmc_rescan calls bus_ops->detect (mmc_sd_detect) and this in turn > calls > >> _mmc_detect_card_removed, which will do the bus_ops->alive and send > CMD13. > >> So in this case, one CMD13 is sent per second, right? > >> Is this the cause of the performance issue? > > > > Yes, You are right. > > Ok, it's a bit hard to understand how this can lead to a noticeable > performance impact, but OK. :) > > >> A thought: if the host hardware does have a GPIO card detect pin > hooked > >> up, would it not be possible to make this pin generate an IRQ whenever > a > >> card is inserted or removed? This is what we do in the MMCI driver, > for > >> instance (mmci_cd_irq). > > > > Our silicones has this pin to do card detect, but some boards don't > generate the interrupt when card is inserted or removed. So I have to use > the poll mode. > > > >> > Yes, some cases to detect GPIO can't be trusted, so I only just > >> implement this callback in eSDHC-of driver. that is to say, just when > the > >> platform support it, this callback can be implement, if not, continue > to > >> send the command CMD13. > >> > >> I'm just wondering how this will affect our system, where we use the > cd > >> GPIO to generate detect jobs on card insert/remove, but where the cd > pin > >> is not 100% synchronized with the electrical connection of the power > and > >> cmd line of the SD-card. So if I remember correctly, the cd pin may > >> report that the card has been removed, but there is still an electric > >> connection and the card is alive... > >> > > I don't see this on our board, when card is inserted or removed, the > register field can reflect this state correctly. > > We see a difference on our boards with this patch, but no functional > change (actually a removed card is detected earlier now), so from my > perspective: > > Reviewed-By: Johan Rudholm <johan.rudholm@xxxxxxxxxxxxxx> > > //Johan -- 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
