lkml.org 
[lkml]   [2011]   [May]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2] sdio: optimized SDIO IRQ handling for single irq
On Wed, 4 May 2011, Per Forlin wrote:

> On 4 May 2011 19:34, Nicolas Pitre <nicolas.pitre@linaro.org> wrote:
> > On Wed, 4 May 2011, Per Forlin wrote:
> >
> >> From: Stefan Nilsson XK <stefan.xk.nilsson@stericsson.com>
> >>
> >> 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.
> >>
> >> Signed-off-by: Per Forlin <per.forlin@linaro.org>
> >> Acked-by: Ulf Hansson <ulf.hansson@stericsson.com>
> >> ---
> >>  drivers/mmc/core/sdio_irq.c |   30 ++++++++++++++++++++++++++++++
> >>  include/linux/mmc/card.h    |    1 +
> >>  2 files changed, 31 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/drivers/mmc/core/sdio_irq.c b/drivers/mmc/core/sdio_irq.c
> >> index b300161..64c4409 100644
> >> --- 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);
> >
> > I think there is little point using a func variable here, especially
> > since you already reference the handler pointer in the if() statement.
> > Hence:
> >
> >        if (card->sdio_single_irq && card->sdio_single_irq->irq_handler) {
> >                card->sdio_single_irq->irq_handler();
> >                return 1;
> >        }
> >
> What do you think about:
> + struct sdio_func *func = card->sdio_single_irq;
> +
> + /*
> + * Optimization, if there is only 1 function interrupt registered
> + * call irq handler directly
> + */
> + if (func) {
> + func->irq_handler(func);
> + return 1;
> + }

Sure, but I'd move the assignment right before the if() in that case for
clarity:

struct sdio_func *func;

/*
* Optimization, if there is only 1 function interrupt registered
* call irq handler directly
*/
func = card->sdio_single_irq;
if (func) {
func->irq_handler(func);
return 1;
}
[...]


Nicolas
\
 
 \ /
  Last update: 2011-05-04 22:25    [W:0.053 / U:0.208 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site