lkml.org 
[lkml]   [2016]   [Apr]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH v2 2/9] drivers: irqchip: Add STM32 external interrupts support
From
Hi Linus,

Sorry for the late reply, I was off last week.

2016-04-08 11:38 GMT+02:00 Linus Walleij <linus.walleij@linaro.org>:
> On Thu, Mar 31, 2016 at 5:09 PM, Maxime Coquelin
> <mcoquelin.stm32@gmail.com> wrote:
>
>> +static void stm32_irq_handler(struct irq_desc *desc)
>> +{
>> + struct irq_domain *domain = irq_desc_get_handler_data(desc);
>> + struct irq_chip_generic *gc = domain->gc->gc[0];
>> + struct irq_chip *chip = irq_desc_get_chip(desc);
>> + unsigned long pending;
>> + int n;
>> +
>> + chained_irq_enter(chip, desc);
>> +
>> + pending = irq_reg_readl(gc, EXTI_PR);
>> + for_each_set_bit(n, &pending, BITS_PER_LONG) {
>> + generic_handle_irq(irq_find_mapping(domain, n));
>> + }
>> +
>> + chained_irq_exit(chip, desc);
>> +}
>
> Is this one of those cases where you should re-read the status register
> on every iteration, so as to avoid exiting and immediately re-entering
> the irq handler?
>
> C.g irq-vic.c:
>
> static int handle_one_vic(struct vic_device *vic, struct pt_regs *regs)
> {
> u32 stat, irq;
> int handled = 0;
>
> while ((stat = readl_relaxed(vic->base + VIC_IRQ_STATUS))) {
> irq = ffs(stat) - 1;
> handle_domain_irq(vic->domain, irq, regs);
> handled = 1;
> }
>
> return handled;
> }

Indeed, it would be better doing it like this.
Do you think I could even do this with two nested loops to reduce the
number of reg accesses?
It would look like this (just compiled, not tested):

static void stm32_irq_handler(struct irq_desc *desc)
{
struct irq_domain *domain = irq_desc_get_handler_data(desc);
struct irq_chip_generic *gc = domain->gc->gc[0];
struct irq_chip *chip = irq_desc_get_chip(desc);
unsigned long pending;
int n;

chained_irq_enter(chip, desc);

while ((pending = irq_reg_readl(gc, EXTI_PR))) {
for_each_set_bit(n, &pending, BITS_PER_LONG) {
generic_handle_irq(irq_find_mapping(domain, n));
}
}

chained_irq_exit(chip, desc);
}

Thanks,
Maxime

\
 
 \ /
  Last update: 2016-04-19 10:21    [W:0.057 / U:1.112 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site