[Bug 58981] New: Bisected regression; boot failure with Radeon 9250 PCI 256MB + KMS

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https://bugzilla.kernel.org/show_bug.cgi?id=58981

           Summary: Bisected regression; boot failure with Radeon 9250 PCI
                    256MB + KMS
           Product: Drivers
           Version: 2.5
    Kernel Version: 2.6.35,3.2.45,3.10-rc2
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Video(DRI - non Intel)
        AssignedTo: drivers_video-dri at kernel-bugs.osdl.org
        ReportedBy: jdietrch at fastmail.fm
        Regression: Yes


I have a Radeon 9250 PCI 256MB video card in my machine. I discovered that this
machine would not boot with 3.2.45 when KMS was enabled by default in the
kernel config. Immediately after the grub menu, the screen would go black and
nothing more would happen. Or sometimes columns of character-sized "marks"
would appear on the screen. In either case, though, the machine would not boot.

So I went back to 2.6.33 and found that booting with KMS did work just fine
there.

So I used git bisect to find where the problem arose, and that pointed to this
commit which was merged for 2.6.35:
commit 6b8b1786a8c29ce6e32298b93ac8d4a18a2b11c4
Author: Jerome Glisse <jglisse at redhat.com>
Date:   Wed Apr 7 10:21:31 2010 +0000

    drm/radeon/kms: enable use of unmappable VRAM V2

I confirmed this result of git bisect by checking out 2.6.35 final and
reverting that one commit, and the resulting kernel booted fine with KMS
enabled by default.

I also tried 3.10-rc2 and that booted fine when I added radeon.modeset=0 to the
kernel commandline.

I will attach files with dmesg output and lspci. Please let me know if there is
anything else I can do. I'll be happy to test a proposed fix if that would be
helpful.

Thank you,
James Dietrich

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