Subject: Re: [PATCH 2.6.12.1 5/12] S2io: Performance improvements

From: Jeff Garzik <[email-masked]>
Date: Thu, 07 Jul 2005 23:08:02 -0400

David S. Miller wrote:
> If you need a PIO to complete in a specific order, you
> have to read it back.  If you need PIO operations to occur

Correct.

A PCI read is the only way to ensure that all the CPU/PCI bridge buffers 
are flushed to the device.

Whenever Arjan and I complain about "PCI posting" problems, we are 
indicating a need for additional readl() calls to ensure 
ordering/flushing.  Delaying immediately after a writel() is a classic 
PCI posting mistake.  Assuming ordering is another.

	Jeff