linux-kernel - 64 bit PCI BAR

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Message-ID: <4CD249DE.1050301@gmail.com>
Date:	Thu, 04 Nov 2010 07:51:26 +0200
From:	Ron Rondis <ron.rondis@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: 64 bit PCI BAR

  Hi,

The following section, from PCI spec, explain the mechanism for getting 
64 bit region size.

"64-bit (memory) Base Address registers can be handled the same, except 
that the second
32-bit register is considered an extension of the first; i.e., bits 
32-63. Software writes
0FFFFFFFFh to both registers, reads them back, and combines the result 
into a 64-bit value.
Size calculation is done on the 64-bit value."

In pci/proce.c the implementation is:

read low bar
write ~0 to low bar
read low bar
write low bar

read high bar
write ~0 to high bar
read high bar
write high bar

Can someone explain the conflict between the spec and the implementation?

Please add me to CC.

Thanks,
Ron

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