> -----Original Message----- > From: Adrian Hunter [mailto:adrian.hun...@intel.com] > Sent: Tuesday, December 13, 2011 4:54 PM > To: Huang Changming-R66093 > Cc: linux-mmc@vger.kernel.org > 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.hun...@intel.com] > >> Sent: Tuesday, December 13, 2011 4:01 PM > >> To: Huang Changming-R66093 > >> Cc: linux-mmc@vger.kernel.org > >> 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-ow...@vger.kernel.org [mailto:linux-mmc- > >>>> ow...@vger.kernel.org] On Behalf Of Adrian Hunter > >>>> Sent: Friday, December 09, 2011 6:03 PM > >>>> To: Huang Changming-R66093 > >>>> Cc: linux-mmc@vger.kernel.org; Huang Changming-R66093 > >>>> Subject: Re: [PATCH 2/4] MMC/SD: Add callback function to detect > >>>> card > >>>> > >>>> On 05/12/11 11:23, r66...@freescale.com wrote: > >>>>> From: Jerry Huang <chang-ming.hu...@freescale.com> > >>>>> > >>>>> 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?
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