Re: [PATCH v2 1/3] PATA host controller driver for ep93xx

[Rafal Prylowski <prylowski@metasoft.pl>]

On 2012-04-03 22:08, Arnd Bergmann wrote:
>>> +static void ep93xx_pata_wait_for_iordy(void __iomem *base)
>>> +{
>>> +     unsigned long deadline = jiffies + msecs_to_jiffies(1000);
>>> +     while (!ep93xx_pata_check_iordy(base) &&
>>> +             time_is_before_jiffies(deadline))
>>> +             cpu_relax();
>>> +}
> 
> Much better for a delay than the previous version. However, it's
> still a busy wait, which is bad for realtime behavior, especially
> since this can potentially take many milliseconds. If possible,
> it should have an msleep() or at least cond_resched() instead of
> the cpu_relax(). Obviously that will only work when no spinlocks
> are held.
> 

Unfortunately, we can't use msleep() or cond_resched() here
- ep93xx_pata_wait_for_iordy() is called from interrupt handler.

Thanks,
RP