Date: Wed, 17 Nov 2004 07:51:36 -0500 (EST)
From: linux-os <linux-os@chaos.analogic.com>
Reply-To: linux-os@analogic.com
To: James.Smart@Emulex.Com
cc: linux-kernel@vger.kernel.org, greg@kroah.com
Subject: Re: Potential issue with some implementations of pci_resource_start()
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Message-ID: <Pine.LNX.4.61.0411170748240.5837@chaos.analogic.com>
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On Tue, 16 Nov 2004 James.Smart@Emulex.Com wrote:

>
> According to Documentation/pci.txt: pci_resource_start() is to return the bus start address of the bar. It should essentially be a portable way to obtain the bar value without reading PCI config space directly.
>
> We have encountered at least 2 platforms (HP Integrity (IA-64) Olympia rx8620 partition, and a dual-processor IBM eServer pSeries p615) - where the contents of pci_resource_start() vary from the contents of the BARs in config space. For example:
> on IA64 Olympia: pci_resource_start(pcidev,0) = 0x00000f0030040000; pci bar0 word 0xf0040004, bar1 word 0x0
> On PPC eServer:  pci_resource_start(pcidev,0) = 0x000003fd80000000; pci bar0 word 0xc0000004, bar1 word 0x0
>
> We have demonstrated this on both the 2.4.21 and 2.6.5 kernels.
>
> Are these platform bugs that need to be corrected ? or is it a change in the pci_resource_start() definition ?
>
> -- James

pic_resource_start() is supposed to give you something that
ioremap() can use. On 64-bit platforms it is unlikely to be
a physical address, but a "cookie" that ioremap() knows about.

If you want the physical address you are going to have to read
the registers directly. It will give you a number that is useless
as an address, though.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.9 on an i686 machine (5537.79 BogoMips).
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