Messages in this thread | | | Date | Fri, 5 Dec 2014 19:41:59 -0800 | From | Ray Jui <> | Subject | Re: [PATCH 2/5] gpio: Cygnus: add GPIO driver |
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On 12/5/2014 6:34 PM, Joe Perches wrote: > On Fri, 2014-12-05 at 18:14 -0800, Ray Jui wrote: >> On 12/5/2014 5:28 PM, Joe Perches wrote: >>> On Fri, 2014-12-05 at 16:40 -0800, Ray Jui wrote: >>>> +static void bcm_cygnus_gpio_irq_handler(unsigned int irq, >>>> + struct irq_desc *desc) >>>> +{ >>>> + struct bcm_cygnus_gpio *cygnus_gpio; >>>> + struct irq_chip *chip = irq_desc_get_chip(desc); >>>> + int i, bit; >>>> + >>>> + chained_irq_enter(chip, desc); >>>> + >>>> + cygnus_gpio = irq_get_handler_data(irq); >>>> + >>>> + /* go through the entire GPIO banks and handle all interrupts */ >>>> + for (i = 0; i < cygnus_gpio->num_banks; i++) { >>>> + unsigned long val = readl(cygnus_gpio->base + >>>> + (i * GPIO_BANK_SIZE) + >>>> + CYGNUS_GPIO_INT_MSTAT_OFFSET); >>>> + if (val) { >>> >>> This if (val) and indentation isn't really necessary >>> >> >> Note for_each_set_bit in this case iterates 32 times searching for bits >> that are set. > > No it doesn't. > > #define for_each_set_bit(bit, addr, size) \ > for ((bit) = find_first_bit((addr), (size)); \ > (bit) < (size); \ > (bit) = find_next_bit((addr), (size), (bit) + 1)) > > find_first_bit: > > * Returns the bit number of the first set bit. > * If no bits are set, returns @size. >
You are right. I reviewed for_each_set_bit but didn't notice find_next_bit may simply return 32 in our case without doing any iterative processing. I will get rid of the redundant if (val) check below.
>> By having the if (val) check here, it can potentially save >> some of such processing in the ISR. I agree with you that it introduces >> one extra indent here but I think it's required. >> >>>> + for_each_set_bit(bit, &val, 32) { >>> >>> for_each_set_bit will effectively do the if above. >>> >>> 32 bit only code? >>> otherwise isn't this endian unsafe? >>> >> >> Will change 'unsigned long val' to 'u32 val'. > > All the bit operations only work on long * > >
Actually, by reviewing the code more deeply, I'm not sure why using for_each_set_bit here is 'endian unsafe'. Isn't that already taken care of by macros in bitops.h? Sorry if I'm still missing something here...
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