** Description changed: + SRU justification: + + Impact: + + Commit "628280f36e4fdbd drm/i915: Sanitize BIOS debugging bits from + PIPECONF" got in the oneiric kernel via upstream, since it fixed a + similar issue as here with an earlier version of the intel VBIOS. With a + newer VBIOS however, the issue is back. Simply reverting the commit + would likely mean breaking other setups. + + this is a critical bug for some our OEM's + + Fix: + + upstream patch 3bcf603f6d5d18b from 3.1 works around a bug in the + CPT/PPT PCH chips, and it was bisected as the commit that fixes the bug + in 3.1 and up. + + Testcase: + + boot a kernel that doesn't have 3bcf603f6d5d18b but has 628280f36e4fdbd + on hw that has a "new enough" VBIOS. + + -- + Issue Description ----------------- Garbage green lines (4-5 pixel lines) appear on top of some Lenovo laptops' screens, persist from boot splash screen to desktop running. Collected Data -------------- Attached are the kernel dmesg, Xorg.0.log and dump files by intel_reg_dumper for oneiric installation with kernel version 3.0.0-19.33 and 3.0.0-20.34, and for precise installation with kernel version 3.2.0-23.26. Observations ------------ 2. This issue only happens on Oneiric with kernel version 3.0.0-20.34 and later ones 3. This issue does not happen on Oneiric with kernel version 3.0.0-19.33 and previous ones 4. This issue does not happen on Precise (12.04) with kernel version 3.2.0-23.36 5. This issue is caused by the upstream commit below: f47166d2 drm/i915: Sanitize BIOS debugging bits from PIPECONF The rationale and original bug description for the above commit can be found at https://bugs.freedesktop.org/show_bug.cgi?id=47271 6. This issue would be gone if the above commit is reverted on Oneiric kernel version 3.0.0-19.33 and later ones 7. There is one other commit below which fixed an issue of the above commit in later kernel version, BUT this commit was verified to have nothing to do with the issue here: a9dcf84b drm/i915: don't clobber the pipe param in sanitize_modesetting 8. This issue was reported to be related to BIOS version as well (see comment #3) 9. There is a WARN_ON() oops on Oneiric with both kernel versions, but this is supposedly an unrelated seperate issue, as it happens in both cases, but presumably fixed in Precise. 10. By comparing the dump contents between two kernels running on Oneiric, the significant difference is the PIPEACONF register 11. By comparing the dump contents between oneiric and precise, there are many more registers with different values Summary ------- We are able to identify the guilty commit, and are able to provide a workaround by reverting the commit or by doing PIPECONF register change for non-relevant machines. However, we are not able to form a correct theory to explain exactly the above observations and to shape a correct patch to fix the root cause.
** Bug watch added: freedesktop.org Bugzilla #56089 https://bugs.freedesktop.org/show_bug.cgi?id=56089 ** Also affects: linux via https://bugs.freedesktop.org/show_bug.cgi?id=56089 Importance: Unknown Status: Unknown -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1041315 Title: Lenovo T530 has a green bar always exists on top of the screen, from initial boot to normal boot, from bootsplash to homescreen, always flashing. To manage notifications about this bug go to: https://bugs.launchpad.net/linux/+bug/1041315/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
