linux-kernel - [PATCH v2] sdio: optimized SDIO IRQ handling for single irq

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Message-Id: <1304525161-14448-2-git-send-email-per.forlin@linaro.org>
Date:	Wed,  4 May 2011 18:06:01 +0200
From:	Per Forlin <per.forlin@...aro.org>
To:	linux-mmc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linaro-dev@...ts.linaro.org
Cc:	Chris Ball <cjb@...top.org>,
	Stefan Nilsson XK <stefan.xk.nilsson@...ricsson.com>,
	Per Forlin <per.forlin@...aro.org>
Subject: [PATCH v2] sdio: optimized SDIO IRQ handling for single irq

From: Stefan Nilsson XK <stefan.xk.nilsson@...ricsson.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@...aro.org>
Acked-by: Ulf Hansson <ulf.hansson@...ricsson.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);
+		return 1;
+	}
+
 	ret = mmc_io_rw_direct(card, 0, 0, SDIO_CCCR_INTx, 0, &pending);
 	if (ret) {
 		printk(KERN_DEBUG "%s: error %d reading SDIO_CCCR_INTx\n",
@@ -186,6 +196,24 @@ static int sdio_card_irq_put(struct mmc_card *card)
 	return 0;
 }
 
+/* If there is only 1 function registered set sdio_single_irq */
+static void sdio_single_irq_set(struct mmc_card *card)
+{
+	struct sdio_func *func;
+	int i;
+
+	card->sdio_single_irq = NULL;
+	if ((card->host->caps & MMC_CAP_SDIO_IRQ) &&
+	    card->host->sdio_irqs == 1)
+		for (i = 0; i < card->sdio_funcs; i++) {
+		       func = card->sdio_func[i];
+		       if (func && func->irq_handler) {
+			       card->sdio_single_irq = func;
+			       break;
+		       }
+	       }
+}
+
 /**
  *	sdio_claim_irq - claim the IRQ for a SDIO function
  *	@func: SDIO function
@@ -227,6 +255,7 @@ int sdio_claim_irq(struct sdio_func *func, sdio_irq_handler_t *handler)
 	ret = sdio_card_irq_get(func->card);
 	if (ret)
 		func->irq_handler = NULL;
+	sdio_single_irq_set(func->card);
 
 	return ret;
 }
@@ -251,6 +280,7 @@ int sdio_release_irq(struct sdio_func *func)
 	if (func->irq_handler) {
 		func->irq_handler = NULL;
 		sdio_card_irq_put(func->card);
+		sdio_single_irq_set(func->card);
 	}
 
 	ret = mmc_io_rw_direct(func->card, 0, 0, SDIO_CCCR_IENx, 0, &reg);
diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
index adb4888..0d64211 100644
--- a/include/linux/mmc/card.h
+++ b/include/linux/mmc/card.h
@@ -145,6 +145,7 @@ struct mmc_card {
 	struct sdio_cccr	cccr;		/* common card info */
 	struct sdio_cis		cis;		/* common tuple info */
 	struct sdio_func	*sdio_func[SDIO_MAX_FUNCS]; /* SDIO functions (devices) */
+	struct sdio_func	*sdio_single_irq; /* SDIO function when only one IRQ active */
 	unsigned		num_info;	/* number of info strings */
 	const char		**info;		/* info strings */
 	struct sdio_func_tuple	*tuples;	/* unknown common tuples */
-- 
1.7.4.1

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