[Bug 194867] New: DRM BUG while initializing cape verde (2nd card)

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=194867

            Bug ID: 194867
           Summary: DRM BUG while initializing cape verde (2nd card)
           Product: Drivers
           Version: 2.5
    Kernel Version: 4.11-rc2
          Hardware: x86-64
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Video(DRI - non Intel)
          Assignee: drivers_video-dri at kernel-bugs.osdl.org
          Reporter: janpieter.sollie at dommel.be
        Regression: No

Created attachment 255215
  --> https://bugzilla.kernel.org/attachment.cgi?id=255215&action=edit
zip file with all listed attachments

There seems to be a logical error while specifying the memory sizes for ttm in
the amdgpu module on the SI architecture:
while the Fiji card boots fine, the Cape Verde card gives a kernel BUG.
dmesg and .config and proposed patch in attachment.
the problem lies in linux/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c: the
determination of the p_size is reduced 0 when the page_shift is too big
I managed to work around the problem when changing the sentence
"adev->gds.mem.total_size >> PAGE_SHIFT)" in  amdgpu_ttm_init to
"(adev->gds.mem.total_size >> PAGE_SHIFT) + 1)", and the same for
"(adev->gds.gws.total_size" and "adev->gds.oa.total_size", though I am not sure
this is the correct solution.  The problem is that my SI card is limited in
memory (I guess) and the page_size is 12

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