On 13/12/11 10:26, Huang Changming-R66093 wrote: > > >> -----Original Message----- >> From: Adrian Hunter [mailto:adrian.hunter@xxxxxxxxx] >> Sent: Tuesday, December 13, 2011 4:01 PM >> To: Huang Changming-R66093 >> Cc: linux-mmc@xxxxxxxxxxxxxxx >> Subject: Re: [PATCH 2/4] MMC/SD: Add callback function to detect card >> >> On 13/12/11 09:25, Huang Changming-R66093 wrote: >>> >>> >>>> -----Original Message----- >>>> From: linux-mmc-owner@xxxxxxxxxxxxxxx [mailto:linux-mmc- >>>> owner@xxxxxxxxxxxxxxx] On Behalf Of Adrian Hunter >>>> Sent: Friday, December 09, 2011 6:03 PM >>>> To: Huang Changming-R66093 >>>> Cc: linux-mmc@xxxxxxxxxxxxxxx; Huang Changming-R66093 >>>> Subject: Re: [PATCH 2/4] MMC/SD: Add callback function to detect card >>>> >>>> On 05/12/11 11:23, r66093@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. >>>> >>>> That should not be true. sdhci.c will not send a command to the card >>>> if the card is not present i.e. see this excerpt from >>>> sdhci_request(): >>>> >>>> >>>> /* If polling, assume that the card is always present. */ >>>> if (host->quirks & SDHCI_QUIRK_BROKEN_CARD_DETECTION) >>>> present = true; >>>> else >>>> present = sdhci_readl(host, SDHCI_PRESENT_STATE) & >>>> SDHCI_CARD_PRESENT; >>>> >>>> if (!present || host->flags & SDHCI_DEVICE_DEAD) { >>>> host->mrq->cmd->error = -ENOMEDIUM; >>>> tasklet_schedule(&host->finish_tasklet); >>>> -- >>> But, for some controller, this field of SDHCI_PRESENT_STATE register is >> reserved and always is 1. When the card is absent, many command will try >> to send to the card, and generate many interrupt. >>> If even controller can detect the card state, if the card is absent as >> you said, this command can't send to card. But, when card is present, >> there will be many command to the card and many interrupts will be >> generated, that will affect the performance. >>> So, I don't think this comment is not correct. >>> >>> >>> >> >> You patch uses (SDHCI_CARD_PRESENT | SDHCI_CARD_CDPL) Does that mean >> SDHCI_CARD_CDPL does work in that case? > No. > The SDHCI_CARD_CDPL[bit13] reflect the pin level: > CDPL: Card detect pin level. This bit reflects the inverse value of the SDHC_CD pin for the card socket. > 0 No card present (SDHC_CD = 1) > 1 Card present (SDHC_CD = 0) > > So, this bit has the same effect as SDHCI_CARD_PRESENT[bit15], the difference is that debouncing is not performed on this bit. > > Freescale's controller supports the card detection, if card is present, none-zero will be returned, otherwise, zero will be returned. > > You can see my other patch [3/4], I add one callback to detect the card state in special platform: if the controller supports card detection, this callback will be performed in special platform (e.g. sdhci-of-esdhc.c) and return the card state (present or absent), if controller doesn't support card detection, this callback will be not performed and return -ENOSYS. OK, but the point is, the request can be stopped in sdhci_request(). Can you just add your callback there? > > > > -- > 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
