Re: [REGRESSION] amdgpu with Thunderbolt eGPU bracket fails since new bridge window alignment calculation code

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

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On Wed, 8 Apr 2026, Jonas Höglund wrote:
> On Tue, 7 Apr 2026, at 07:26, Ilpo Järvinen wrote:
> >> 
> >> Here are dmesg logs (with the appropriate dyndbg cmdline flag) for both
> >> cases, in case it's useful:
> >> 
> >> https://up.firefly.nu/pub/amdgpu-egpu-crash-7.0.0-rc6.dmesg.txt
> >> https://up.firefly.nu/pub/amdgpu-egpu-good-pci-resource.dmesg.txt
> >> 
> >> 
> >> That's good enough on my end, knowing the issue is addressed already
> >> upstream and slated for 7.1.  I'm happy to test anything else if it'd
> >> be useful (for eventual backports or so), but otherwise I think I'll
> >> just pick thoes patches from the pci/resource tree for now.
> >
> > Hi,
> >
> > Thanks. It certainly looks the commit dc4b4d04e1ca ("PCI: Prevent 
> > shrinking bridge window from its required size") I referred to above might 
> > indeed help here (For Thorsten's convinience: as mentioned above, it is 
> > currently in the pci/resource branch slated for 7.1).
> >
> > With the extra debug enabled, "shrunken by" lines appear in the log which 
> > indicates the hotplug memory distribution algorithm goes to mess with the 
> > calculated bridge window sizes in between resource sizing and resource 
> > assignment and my fix aims to prevent that from happening.
> >
> 
> Sorry, I'm slightly unsure what I should be building and testing here.
> Is it fine to check out the pci/resource branch as it is and test that,
> or should I make sure to pick the patches from that branch atop e.g.
> 7.0-rc6?

The latter is better because pci/resources is based at 7.0-rc1 and since 
then, there have been two fixes that went through -rc series (I'm not sure 
if either is relevant for your usecase, probably not but to be on safe 
side it's better to include them as well).

BUT, it's easier to just merge pci/resource on top of -rc6 so you don't 
need to pick the patches by hand). I think the merge should go cleanly.

> > If that fix does not help or does not fully solve the issue, please do 
> > take a new log with that patch included into the kernel (preferrably with 
> > all the fixes that are currently in the pci/resource branch so we don't 
> > hit yet another issue that already has a fix). If you need to take more 
> > logs, please include also /proc/iomem dump (as figuring the iomem layout 
> > from dmesg is pretty tedious and error prone).
> >
> 
> Will include /pro/iomem with future dumps.
> 
> 
> > Also if you see this line, it's worth to posting the log (even if things 
> > would appear as working):
> >
> > amdgpu 0000:3e:00.0: Not enough PCI address space for a large BAR.
> >
> > ...I'll see if I can somehow improve that as well (not a guarantee but 
> > it's still worth taking a look, it appears also in the case you labeled 
> > "good").
> >
> 
> Ok. Yeah, "good" was a bit of a misnomer, was simply meant as short for
> "docks successfully" (as far as the visual feedback as a user goes).
> 
> 
> I'll get to building and testing after confirmation what I should build.
> 
> Thanks,
> Jonas
> 

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