Re: [PATCH 2/2] mmc: dw_mmc: check card present before starting request

[Shawn Lin]

å 2016/5/27 11:46, Jaehoon Chung åé:
> Hi Shawn,
>
> On 05/27/2016 12:02 PM, Shawn Lin wrote:
> > The main reason to add this check is to avoid unnecessary
> > mmc_request like the on-going cmd and the corresponding sbc
> > if the card is removed. Although we have already checked this in
> > dw_mci_handle_cd for runtime usage of sd card and dw_mci_init_slot
> > for noremovable devices, but there is a timing gap before it really
> > calls dw_mci_get_cd as mmc_detect_change needs some delay here.
> >
> > Another gain here is that we could save some checkings of card status
> > after sd card been removed.
> >
> > Signed-off-by: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>
> > ---
> >
> >  drivers/mmc/host/dw_mmc.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> > index cb30e91..8eb7898 100644
> > --- a/drivers/mmc/host/dw_mmc.c
> > +++ b/drivers/mmc/host/dw_mmc.c
> > @@ -105,6 +105,7 @@ struct idmac_desc {
> >  static bool dw_mci_reset(struct dw_mci *host);
> >  static bool dw_mci_ctrl_reset(struct dw_mci *host, u32 reset);
> >  static int dw_mci_card_busy(struct mmc_host *mmc);
> > +static int dw_mci_get_cd(struct mmc_host *mmc);
> >
> >  #if defined(CONFIG_DEBUG_FS)
> >  static int dw_mci_req_show(struct seq_file *s, void *v)
> > @@ -1255,7 +1256,7 @@ static void dw_mci_request(struct mmc_host *mmc, struct mmc_request *mrq)
> >  	 */
> >  	spin_lock_bh(&host->lock);
> >
> > -	if (!test_bit(DW_MMC_CARD_PRESENT, &slot->flags)) {
> > +	if (!dw_mci_get_cd(mmc)) {
> >  		spin_unlock_bh(&host->lock);
> >  		mrq->cmd->error = -ENOMEDIUM;
> >  		mmc_request_done(mmc, mrq);
>
> I think spin_lock/unlock_bh() should be removed at here.

yes, we should hole the lock before dw_mci_queue_request as
dw_mci_get_cd release it, in which state we do the minmum changes
for achieving what we need here.

I will fix it.

> Instead, Can it locate before calling dw_mci_queue_request()?
>
> Anyway, it looks good to me.
>
> Best Regards,
> Jaehoon Chung
>
> >


--
Best Regards
Shawn Lin