linux-kernel - Re: [PATCH] x86/pci: intel ioh need to subtract mmconf range

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Message-ID: <4B563839.3000203@kernel.org>
Date:	Tue, 19 Jan 2010 14:54:49 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Bjorn Helgaas <bjorn.helgaas@...com>
CC:	Jeff Garrett <jeff@...rrett.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	linux-kernel@...r.kernel.org, Len Brown <lenb@...nel.org>,
	linux-acpi@...r.kernel.org, linux-pci@...r.kernel.org,
	David Airlie <airlied@...ux.ie>
Subject: Re: [PATCH] x86/pci: intel ioh need to subtract mmconf range

On 01/19/2010 02:52 PM, Bjorn Helgaas wrote:
> On Tuesday 19 January 2010 12:57:39 pm Yinghai Lu wrote:
>> On 01/19/2010 11:42 AM, Jeff Garrett wrote:
>>> On Fri, Jan 15, 2010 at 10:14:17AM -0800, Jesse Barnes wrote:
>>>> On Thu, 14 Jan 2010 16:39:13 -0800
>>>> Yinghai Lu <yinghai@...nel.org> wrote:
>>>>
>>>>> On 01/14/2010 03:49 PM, Bjorn Helgaas wrote:
>>>>>> On Thursday 14 January 2010 04:38:08 pm Yinghai Lu wrote:
>>>>>>> On 01/14/2010 03:09 PM, Bjorn Helgaas wrote:
>>>>>>>> On Thursday 14 January 2010 03:46:35 pm Yinghai Lu wrote:
>>>>>>>>>
>>>>>>>>> Bjorn pointed out we need to remove mmconf range
>>>>>>>>>
>>>>>>>>> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
>>>>>>>>>
>>>>>>>>> ---
>>> ...
>>>>>>>>
>>>>>>>> This can't be right, can it?  Let's say the kernel was built with
>>>>>>>> CONFIG_PCI_MMCONFIG turned off, or the user used "pci=nommconf",
>>>>>>>> or the kernel decides not to use MMCONFIG for some other reason.
>>>>>>>>
>>>>>>>> In that case, the hardware may still be configured to support
>>>>>>>> MMCONFIG, but the pci_mmcfg_list will be empty, so your code will
>>>>>>>> leave the window alone.  We might assign some of that MMCONFIG
>>>>>>>> space to a device, but the hardware will route it to MMCONFIG,
>>>>>>>> not to the device.
>>>>>>>
>>>>>>> so if there is mmconf specified, we just skip the whole function?
>>>>>>
>>>>>> No, I'm saying that intel-bus.c must ALWAYS remove the MMCONFIG
>>>>>> region from the host bridge apertures, even if Linux isn't using
>>>>>> MMCONFIG.
>>>>>>
>>>>>> That means intel-bus.c has to be smart enough to figure out on its
>>>>>> own what the MMCONFIG area is.  It can't depend on mmconfig-shared.c
>>>>>> to do it, because mmconfig-shared.c might not be there.
>>>>>
>>>>> that seems go too far away...
>>>>>
>>>>> Subject: [PATCH -v2] x86/pci: intel ioh need to subtrac mmconf range
>>>>>
>>>>> Bjorn pointed out we need to remove mmconf range
>>>>>
>>>>> -v2: if mmconf is not there, get out early.
>>>>>
>>>>> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
>>>>>
>>>>> ---
>>> ...
>>>>
>>>> This goes against the real intent of intel_bus.c doesn't it?  When we
>>>> first added it, the thought was that it would be a purely native way of
>>>> getting at bridge window information and not rely on firmware.  If
>>>> you're going to make it dependent on MMCONFIG now, why not trust other
>>>> firmware tables as well, like _CRS?
>>>>
>>>> The MMCONFIG ranges are pretty easy to get at, the public docs have
>>>> info about the registers that control the MMCONFIG decode ranges, so
>>>> you should be able to read them out and add them to this file,
>>>> preserving the original intent.
>>>
>>> I did attempt a bisection last week, but my pared down config kept
>>> hitting a sysfs_create_file panic.  I didn't succeed.
> 
> I don't think there's any need to bisect this; sorry I didn't
> mention this earlier.
> 
> 2.6.32 didn't include intel-bus.c, so the kernel just assumed that
> all non-RAM addresses got routed to the PCI bus.  This would have
> included the [mem 0xd0000000-0xdfffffff] used by your Radeon device,
> which explains why it would work there.
> 
> After 2.6.32, we added intel-bus.c, which reads some of the host
> bridge aperture information from the chipset.  This is apparently
> missing something, because intel-bus.c didn't find that region,
> so Linux thought the Radeon resource was wrong and disabled it,
> which broke it.
> 
>>> Should I try the v2 patch above?  What tree is it against?
>>
>> maybe later with -tip tree + pci/linux-next.
> 
> Yinghai, did you figure out how to discover the [mem 0xd0000000-0xdfffffff]
> region in intel-bus.c?  Jeff's video isn't going to work without that.
> 

didn't get info from vendor yet.

looks there is some bit that will enable those register, otherwise those register should not be used.

YH

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