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From: =?ISO-8859-2?Q?Micha=B3_Miros=B3aw?= <mirqus@gmail.com>
Date: Wed, 4 May 2011 18:23:38 +0200
Message-ID: <BANLkTi=LsmSepyUMbO7q2hG5-HWbRduO+Q@mail.gmail.com>
Subject: Re: [PATCH v2] sdio: optimized SDIO IRQ handling for single irq
To: Per Forlin <per.forlin@linaro.org>
Cc: linux-mmc@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, linaro-dev@lists.linaro.org,
        Chris Ball <cjb@laptop.org>,
        Stefan Nilsson XK <stefan.xk.nilsson@stericsson.com>
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2011/5/4 Per Forlin <per.forlin@linaro.org>:
> 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.
>
[...]
> --- 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

in sdio_claim_irq():

  card->func->irq_handler = ...
  if (host->sdio_irqs == 1)
    card->sdio_irq_func = func;
  else
    card->sdio_irq_func = NULL;

in sdio_release_irq():

  card->sdio_irq_func = NULL;
  card->func->irq_handler = ...
  sdio_card_irq_put();
  if (host->sdio_irqs == 1)
    sdio_single_irq_set(func->card);

in struct mmc_card:
  struct sdio_func ? ? ? ?*sdio_irq_func;

Best Regards,
Micha? Miros?aw
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