On 13/12/11 11:55, Huang Changming-R66093 wrote: > > >> -----Original Message----- >> From: Adrian Hunter [mailto:adrian.hunter@xxxxxxxxx] >> Sent: Tuesday, December 13, 2011 4:54 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 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? > Why can the request be stopped? Just because of card absent or SDHCI_DEVICE_DEAD? Yes, both -- 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
