On Wed, 4 May 2011, Per Forlin wrote:
> 2011/5/4 Michał Mirosław <mirqus@xxxxxxxxx>:
> > 2011/5/4 Per Forlin <per.forlin@xxxxxxxxxx>:
> >> From: Stefan Nilsson XK <stefan.xk.nilsson@xxxxxxxxxxxxxx>
> >>
> >> If there is only 1 function registered it is possible to
> >> improve performance by directly calling the irq handler
> >> and avoiding the overhead of reading the CCCR registers.
> >>
> > [...]
> >> --- a/drivers/mmc/core/sdio_irq.c
> >> +++ b/drivers/mmc/core/sdio_irq.c
> >> @@ -32,6 +32,16 @@ static int process_sdio_pending_irqs(struct mmc_card *card)
> >> int i, ret, count;
> >> unsigned char pending;
> >>
> >> + /*
> >> + * Optimization, if there is only 1 function registered
> >> + * call irq handler directly
> >> + */
> >> + if (card->sdio_single_irq && card->sdio_single_irq->irq_handler) {
> >> + struct sdio_func *func = card->sdio_single_irq;
> >> + func->irq_handler(func);
> >> + return 1;
> >> + }
> > [...]
> >
> > The second condition can be avoided:
> >
> > in process_sdio_pending_irqs():
> >
> > if (card->sdio_irq_func)
> > call handler and return
> >
> I added the second condition as a sanity check. Same check is used in
> the main for loop
> > ret = -EINVAL;
> > } else if (func->irq_handler) {
> > func->irq_handler(func);
> Is the second check necessary here?
Yes because we want to be notified if the hardware returns pending
interrupt flags for interrupts we didn't claim.
> > in sdio_claim_irq():
> >
> > card->func->irq_handler = ...
> > if (host->sdio_irqs == 1)
> > card->sdio_irq_func = func;
> > else
> > card->sdio_irq_func = NULL;
> I wanted to keep it simple and use same function in claim and release.
> Your code looks nice.
> Is if safe to not check the condition "(card->host->caps &
> MMC_CAP_SDIO_IRQ)". What happens if the SDIO is in polling mode?
You cannot avoid checking MMC_CAP_SDIO_IRQ. If it isn't set the CCCr
register must be polled in all cases.
Nicolas
