From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jon Hunter Subject: [PATCH 3/5] gpio/omap: optimise interrupt service routine Date: Thu, 4 Apr 2013 15:16:14 -0500 Message-ID: <1365106576-31816-4-git-send-email-jon-hunter@ti.com> References: <1365106576-31816-1-git-send-email-jon-hunter@ti.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-Reply-To: <1365106576-31816-1-git-send-email-jon-hunter@ti.com> Sender: linux-omap-owner@vger.kernel.org To: Linus Walleij , Grant Likely , Santosh Shilimkar , Kevin Hilman Cc: device-tree , linux-omap , linux-arm , Jon Hunter , Felipe Balbi List-Id: devicetree@vger.kernel.org The OMAP GPIO interrupt service routine is checking each bit in the GPIO interrupt status register to see which bits are set. It is not efficient to check every bit especially if only a few bits are set. Therefore, instead of checking every bit use the __ffs() function, which returns the location of the first set bit, to find all the set bits. This optimisation was suggested-by and developed in collaboration with Felipe Balbi. Cc: Felipe Balbi Signed-off-by: Jon Hunter --- drivers/gpio/gpio-omap.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c index 5af7acd..685e850 100644 --- a/drivers/gpio/gpio-omap.c +++ b/drivers/gpio/gpio-omap.c @@ -689,7 +689,7 @@ static void gpio_irq_handler(unsigned int irq, struct irq_desc *desc) { void __iomem *isr_reg = NULL; u32 isr; - unsigned int i; + unsigned int bit; struct gpio_bank *bank; int unmasked = 0; struct irq_chip *chip = irq_desc_get_chip(desc); @@ -730,9 +730,9 @@ static void gpio_irq_handler(unsigned int irq, struct irq_desc *desc) if (!isr) break; - for (i = 0; isr != 0; isr >>= 1, i++) { - if (!(isr & 1)) - continue; + while (isr) { + bit = __ffs(isr); + isr &= ~(1 << bit); /* * Some chips can't respond to both rising and falling @@ -741,10 +741,10 @@ static void gpio_irq_handler(unsigned int irq, struct irq_desc *desc) * to respond to the IRQ for the opposite direction. * This will be indicated in the bank toggle_mask. */ - if (bank->toggle_mask & (1 << i)) - _toggle_gpio_edge_triggering(bank, i); + if (bank->toggle_mask & (1 << bit)) + _toggle_gpio_edge_triggering(bank, bit); - generic_handle_irq(irq_find_mapping(bank->domain, i)); + generic_handle_irq(irq_find_mapping(bank->domain, bit)); } } /* if bank has any level sensitive GPIO pin interrupt -- 1.7.10.4