From: prylowski@metasoft.pl (Rafal Prylowski)
Date: Wed, 04 Apr 2012 14:40:34 +0200
Subject: [PATCH v2 1/3] PATA host controller driver for ep93xx
In-Reply-To: <201204032008.00509.arnd@arndb.de>
References: <4F7B0C54.8010804@metasoft.pl> <4F7B0CEF.2040307@metasoft.pl>
 <ADE657CA350FB648AAC2C43247A983F0020698409E29@AUSP01VMBX24.collaborationhost.net>
 <201204032008.00509.arnd@arndb.de>
Message-ID: <4F7C4142.1010709@metasoft.pl>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

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