linux-kernel - Re: [Patch v2] Make PCI extended config space (MMCONFIG) a driver opt-in

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Message-ID: <47742498.1060900@tragetaschen.dyndns.org>
Date:	Thu, 27 Dec 2007 23:18:00 +0100
From:	Kai Ruhnau <kai@...getaschen.dyndns.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Loic Prylli <loic@...i.com>, Robert Hancock <hancockr@...w.ca>,
	Jeff Garzik <jeff@...zik.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	gregkh@...e.de, linux-pci <linux-pci@...ey.karlin.mff.cuni.cz>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Martin Mares <mj@....cz>, Matthew Wilcox <matthew@....cx>
Subject: Re: [Patch v2] Make PCI extended config space (MMCONFIG) a driver
 opt-in

Linus Torvalds wrote:
> On Thu, 27 Dec 2007, Linus Torvalds wrote:
>   
>> Kai, can you try that? Just remove the call to pci_enable_crs() in 
>> pci_scan_bridge() in drivers/pci/probe.c, and see if mmconfig starts 
>> working for you?
>>     
>
> We could also make the error handling more permissive, and just check for 
> the low 16 bits, which is the part that the CRS spec mentions the actual 
> value for. The whole vendor ID of 0x0001 is mentioned int he CRS spec as 
> being explicitly chosen exactly because it's invalid.
>
> That said, given that we don't actually reap any benefits from CRS support 
> right now *anyway*, I think the right thing to do is disable it by 
> default. But it would be interesting to know if this patch makes it work 
> on those ATI bridges..
>
> 		Linus
>
> ---
>  drivers/pci/probe.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 2f75d69..94cd3a4 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -908,7 +908,7 @@ pci_scan_device(struct pci_bus *bus, int devfn)
>  		return NULL;
>  
>  	/* Configuration request Retry Status */
> -	while (l == 0xffff0001) {
> +	while ((l & 0xffff) == 0x0001) {
>  		msleep(delay);
>  		delay *= 2;
>  		if (pci_bus_read_config_dword(bus, devfn, PCI_VENDOR_ID, &l)

That one did not work out so well.
I reenabled the call to pci_enable_crs() and changed the line as above.
That resulted in two timeouts (from dmesg):

[....]
ACPI: Interpreter enabled
ACPI: (supports S0 S3 S4 S5)
ACPI: Using IOACPI for interrupt routing
ACPI: PCI Root Bridge [PCI0] (0000:00)
Device 0000:01:00.0 not responding
Device 0000:02:00.0 not responding
[....]

Then, the kernel boots up normally except of graphics and network card
not showing up at all in lspci.

Kai

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