> -----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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