** Tags added: kernel-da-key
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https://bugs.launchpad.net/bugs/1698706
Title:
Quirk for non-compliant PCI bridge on HiSilicon D05 board
Status in linux package in Ubuntu:
Fix Committed
Status in linux source package in Zesty:
Fix Committed
Bug description:
SRU Justification
[Impact]
Xorg autodetection does not work on HiSilicon D05 boards.
[Fix]
The HiSilicon D05 board has some PCI bridges (PCI ID 19e5:1610) that are not
spec-compliant: they do not set the VGA Enable bit when a VGA card is behind
the bridge. This stops vgaarb setting the device as a boot vga device, breaking
Xorg auto-detection. [0]
Despite this, the hibmc VGA card (PCI ID 19e5:1711) is known to work
when behind these bridges.
Provide a quirk so that this combination of bridge and card works.
[Testcase]
On an affected board, run:
# find /sys/devices -name boot_vga -exec cat \{\} \;
This should print 0 without this patch and 1 with this patch.
[Regression Potential]
There is a risk with overriding the VGA arbiter that adding additional VGA
cards to the board may go wrong somehow. The fixup specifically tests for the
bridge and card on the board, so regressions should be limited to that
combination of bridge and card.
[Notes]
HiSilicon is hoping to have 16.04.3 HWE kernel support their board, hence the
submission of this patch before it has been accepted upstream. The patch has
been submitted upstream and I will continue to work with upstream to land it.[1]
[0] https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/1691991 - this
bug tracked debugging of a segfault and then this issue. Comments 25
(https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/1691991/comments/25)
and 31 onwards detail this issue.
[1] https://patchwork.ozlabs.org/patch/778054/
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