[PATCH 3/5] gpio/omap: optimise interrupt service routine

[Felipe Balbi]

On Thu, Apr 04, 2013 at 03:16:14PM -0500, Jon Hunter wrote:
> 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 <balbi at ti.com>
> 
> Signed-off-by: Jon Hunter <jon-hunter at ti.com>

looks alright:

Reviewed-by: Felipe Balbi <balbi at ti.com>

> ---
>  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
> 

-- 
balbi
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