> 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. > 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. > I think function _mmc_detect_card_removed aim to verify whether card > still exist by communicate with card. [jerry] There are some codes to verify whether card still exist by communication with card in function "sdhci_request". Function "mmc_sd_detect", "mmc_sdio_detect" and "mmc_detect" will call this function to detect the card. > Thanks > Kevin > > > Best Regards > > Jerry Huang > > > > > >> -----Original Message----- > >> From: Ulf Hansson [mailto:ulf.hansson@xxxxxxxxxx] > >> Sent: Wednesday, March 20, 2013 5:29 PM > >> To: Huang Changming-R66093 > >> Cc: linux-mmc@xxxxxxxxxxxxxxx; Chris Ball > >> Subject: Re: [PATCH 1/3i v6] MMC/SD: Add callback function to detect > >> card > >> > >> On 20 March 2013 10:04, Huang Changming-R66093 <r66093@xxxxxxxxxxxxx> > >> wrote: > >> > They have different function, Kevin's patch is for slowly removed, > >> > it > >> can't resolve the performance issue. > >> > >> Actually I am not sure what your patch is trying to solve. Kevin's > >> patch makes sense. > >> > >> Can you elaborate a bit on what performance issues that needs to be > >> considered during card removal? > >> > >> > First, we should use get_cd to get the card status, if it is not > >> supported, then use the alive to send CMD13. > >> > For the driver that supports get_cd, the system performance can > upgrade. > >> > Maybe Kevin can base on this patch. > >> > > >> > Best Regards > >> > Jerry Huang > >> > > >> > > >> >> -----Original Message----- > >> >> From: Ulf Hansson [mailto:ulf.hansson@xxxxxxxxxx] > >> >> Sent: Wednesday, March 20, 2013 4:43 PM > >> >> To: Huang Changming-R66093 > >> >> Cc: linux-mmc@xxxxxxxxxxxxxxx; Chris Ball > >> >> Subject: Re: [PATCH 1/3i v6] MMC/SD: Add callback function to > >> >> detect card > >> >> > >> >> On 20 March 2013 06:41, <Chang-Ming.Huang@xxxxxxxxxxxxx> wrote: > >> >> > From: Jerry Huang <Chang-Ming.Huang@xxxxxxxxxxxxx> > >> >> > > >> >> > In order to check whether the card has been removed, the > >> >> > function > >> >> > mmc_send_status() will send command CMD13 to card and ask the > >> >> > card to send its status register to sdhc driver, which will > >> >> > generate many interrupts repeatedly and make the system > performance bad. > >> >> > From the performance test on Freescale's board (such as Iozone > >> >> > for SD), the performance will degrade about 4~6%. > >> >> > > >> >> > There is one another way to get this information, which is to > >> >> > read the register PRSSTAT and check the bit CDPL or CINS. > >> >> > If the card is present, these two bit will set to one. > >> >> > Therefore, add callback function get_cd() to check whether the > >> >> > card has been inserted/removed when the driver supports this > feature. > >> >> > If the card is present, 0 will return, if the card is absent, 1 > >> >> > will > >> >> return. > >> >> > If the controller will not support this feature, -ENOSYS will > return. > >> >> > > >> >> > Signed-off-by: Jerry Huang <Chang-Ming.Huang@xxxxxxxxxxxxx> > >> >> > Reviewed-by: Johan Rudholm <johan.rudholm@xxxxxxxxxxxxxx> > >> >> > Reviewed-by: Anton Vorontsov <cbouatmailru@xxxxxxxxx> > >> >> > CC: Chris Ball <cjb@xxxxxxxxxx> > >> >> > --- > >> >> > changes for v2: > >> >> > - when controller don't support get_cd, return -ENOSYS > >> >> > - add the CC > >> >> > changes for v3: > >> >> > - enalbe the controller clock in platform, instead of > >> >> > core changes for v4: > >> >> > - move the detect code to core.c according to the new > >> >> > structure changes for v5: > >> >> > - reviewed by Anton and Johan, add the reviewed-by. > >> >> > changes for v6: > >> >> > - add more comment. > >> >> > > >> >> > drivers/mmc/core/core.c | 16 ++++++++++++++-- > >> >> > 1 file changed, 14 insertions(+), 2 deletions(-) > >> >> > > >> >> > diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c > >> >> > index 08a3cf2..e225deb 100644 > >> >> > --- a/drivers/mmc/core/core.c > >> >> > +++ b/drivers/mmc/core/core.c > >> >> > @@ -2280,7 +2280,7 @@ static int mmc_rescan_try_freq(struct > >> >> > mmc_host *host, unsigned freq) > >> >> > > >> >> > int _mmc_detect_card_removed(struct mmc_host *host) { > >> >> > - int ret; > >> >> > + int ret = -ENOSYS; > >> >> > > >> >> > if ((host->caps & MMC_CAP_NONREMOVABLE) || > >> >> >!host->bus_ops- > >> >> >alive) > >> >> > return 0; > >> >> > @@ -2288,7 +2288,19 @@ int _mmc_detect_card_removed(struct > >> >> >mmc_host > >> >> *host) > >> >> > if (!host->card || mmc_card_removed(host->card)) > >> >> > return 1; > >> >> > > >> >> > - ret = host->bus_ops->alive(host); > >> >> > + /* First, try host-controller's card detect callback */ > >> >> > + if (host->ops->get_cd) { > >> >> > + ret = host->ops->get_cd(host); > >> >> > + /* > >> >> > + * The return value from get_cd: 1 for present, > >> >> > + 0 for > >> >> absent, > >> >> > + * we need to convert it to: 1 for absent, 0 for > >> >> present. > >> >> > + */ > >> >> > + if (ret >= 0) > >> >> > + ret = !ret; > >> >> > + } > >> >> > + /* If failed, back to the bus_ops alive() callback */ > >> >> > + if (ret < 0) > >> >> > + ret = host->bus_ops->alive(host); > >> >> > if (ret) { > >> >> > mmc_card_set_removed(host->card); > >> >> > pr_debug("%s: card remove detected\n", > >> >> mmc_hostname(host)); > >> >> > >> >> I guess this already has been fixed by Kevin's patch below. > >> >> > >> >> http://article.gmane.org/gmane.linux.kernel.mmc/19481 > >> >> > >> >> > -- > >> >> > 1.7.9.5 > >> >> > > >> >> > > >> >> > -- > >> >> > 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 > >> >> > >> >> 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 -- 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
