[PATCH] ARM: Gemini: Add support for PCI BUS
Sergei Shtylyov
sshtylyov at mvista.com
Mon Dec 6 05:51:52 EST 2010
Hello.
On 29-11-2010 19:45, Arnd Bergmann wrote:
>>> The I/O ordering is probably not what you think it is.
>>> There is no ordering guarantee between __raw_writel and
>>> spin_lock/spin_unlock, so you really should be using
>>> readl/writel.
>> No he really should NOT use readl/writel. The ONLY difference
>> between readl/writel and __raw_readl/__raw_writel is endianess
>> conversion. __raw_*l is not doing it. Which to use depend only
>> on HW.
> There are many differences between readl and __raw_readl, including
> * __raw_readl does not have barriers and does not serialize with
> spinlocks, so it breaks on out-of-order CPUs.
> * __raw_readl does not have a specific endianess, while readl is
> fixed little-endian,
I know I'm late but readl()/writel() are CPU-endian, not LE.
WBR, Sergei
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