Re: [PATCH 2/4 v4] MMC/SD: Add callback function to detect card

[Aaron Lu <aaron.lu@amd.com>]

Hi,

On Fri, Jan 13, 2012 at 02:25:11AM +0000, Huang Changming-R66093 wrote:
> Hi, Chris,
> Could you have any comment about this patch?
> Can it go into 3.3 or 3.4?
> 
> Thanks
> Jerry Huang
> > -----Original Message-----
> > From: Huang Changming-R66093
> > Sent: Tuesday, December 27, 2011 4:01 PM
> > To: linux-mmc@vger.kernel.org
> > Cc: Huang Changming-R66093; Chris Ball
> > Subject: [PATCH 2/4 v4] MMC/SD: Add callback function to detect card
> > 
> > From: Jerry Huang <Chang-Ming.Huang@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.

For sd hosts, this should only happen for hosts which have
SDHCI_QUIRK_BROKEN_CARD_DETECTION set.

> > 
> > Therefore, add callback function get_cd() to check whether
> > the card has been removed when the driver has this callback function.

I don't quite get the meaning of cd, what does get_cd suppose to mean?

> > 
> > If the card is present, 1 will return, if the card is absent, 0 will
> > return.
> > If the controller will not support this feature, -ENOSYS will return.

What about get_present, return 0 for present, and return error code
otherwise like the alive function does.

> > 
> > Signed-off-by: Jerry Huang <Chang-Ming.Huang@freescale.com>
> > CC: Chris Ball <cjb@laptop.org>
> > ---
> > 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
> > 
> >  drivers/mmc/core/core.c |   10 ++++++++--
> >  1 files changed, 8 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> > index 6db6621..d570c72 100644
> > --- a/drivers/mmc/core/core.c
> > +++ b/drivers/mmc/core/core.c
> > @@ -2060,7 +2060,7 @@ static int mmc_rescan_try_freq(struct mmc_host
> > *host, unsigned freq)
> > 

snip
> >  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;
> > @@ -2068,7 +2068,13 @@ 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);
> > +	if (host->ops->get_cd) {
> > +		ret = host->ops->get_cd(host);
> > +		if (ret >= 0)
> > +			ret = !ret;
> > +	}
> > +	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));
> > --
> > 1.7.5.4

And the code can be changed to something like:
	if (host->ops->get_present)
		ret = host->ops->get_present(host);
	else
		ret = host->bus_ops->alive(host);
	if (ret) {
		mmc_card_set_removed(host->card);
  		pr_debug("%s: card remove detected\n", mmc_hostname(host));
	}


Does this make sense?

-Aaron

> 
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