> > 2012/11/2 Huang Changming-R66093 <[email protected]>: > > 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. > > 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. -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
