The commit in question (8f4b1068e7fc3df1a77ac8151767e56b208cc87f)
introduces the following logic in intel_mode_valid function
(drivers/gpu/drm/i915/display/intel_display.c):
+ if (DISPLAY_VER(dev_priv) >= 5) {
+ if (mode->hdisplay < 64 ||
+ mode->htotal - mode->hdisplay < 32)
+ return MODE_H_ILLEGAL;
+
+ if (mode->vtotal - mode->vdisplay < 5)
+ return MODE_V_ILLEGAL;
+ } else {
+ if (mode->htotal - mode->hdisplay < 32)
+ return MODE_H_ILLEGAL;
+
+ if (mode->vtotal - mode->vdisplay < 3)
+ return MODE_V_ILLEGAL;
+ }
In case of this particular hardware the following condition is met:
if (mode->htotal - mode->hdisplay < 32)
return MODE_H_ILLEGAL;
with values: htotal==830 and hdisplay=800 resulting in returning
MODE_H_ILLEGAL.
I am looking into where does the htotal value come from.
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https://bugs.launchpad.net/bugs/2044131
Title:
i915 regression introduced with 5.5 kernel
Status in linux package in Ubuntu:
New
Bug description:
There is a regression preventing a user to upgrade from 5.4 kernel to
anything that's higher than 5.5. When using such kernel the image orientation
is wrong (rotated by 90°C). Also the kernel log contains:
wrz 15 09:19:49 desktop kernel: i915 0000:00:02.0: [drm] Unknown revid 0x06
wrz 15 09:19:49 desktop kernel: rtw_8821ce 0000:01:00.0: Firmware version
24.8.0, H2C version 12
wrz 15 09:19:49 desktop kernel: Console: switching to colour dummy device
80x25
wrz 15 09:19:49 desktop kernel: i915 0000:00:02.0: vgaarb: deactivate vga
console
wrz 15 09:19:49 desktop kernel: i915 0000:00:02.0: [drm] couldn't get memory
information
wrz 15 09:19:49 desktop kernel: i915 0000:00:02.0: vgaarb: changed VGA
decodes: olddecodes=io+mem,decodes=io+mem:o>
wrz 15 09:19:49 desktop kernel: i915 0000:00:02.0: [drm] Finished loading DMC
firmware i915/glk_dmc_ver1_04.bin (v>
wrz 15 09:19:49 desktop kernel:
================================================================================
wrz 15 09:19:49 desktop kernel: UBSAN: array-index-out-of-bounds in
/build/linux-hwe-5.15-DZkSuT/linux-hwe-5.15-5.>
wrz 15 09:19:49 desktop kernel: index 5 is out of range for type 'u32 [5]'
(full stack trace attached)
The video hardware in use is:
00:02.0 VGA compatible controller [0300]: Intel Corporation UHD Graphics 605
[8086:3185] (rev 06) (prog-if 00 [VGA controller])
(...)
Kernel driver in use: i915
Kernel modules: i915
The user wanted to upgrade from bionic to focal with HWE kernel (they
needed it due to some networking hardware they wanted to have
supported by the newer kernel).
The user was testing mainline stable kernels and noticed that the last
working kernel was the 5.4 series, while anything starting from 5.5
and above is BROKEN (symptoms as described in the first paragraph
above).
Together with the user we have run a bisection between v5.4 and v5.5 on the
upstream stable kernel and we were able to identify the first broken commit to
be:
8f4b1068e7fc3df1a77ac8151767e56b208cc87f drm/i915: Check some transcoder
timing minimum limits
To confirm I have reverted this change on top of the HWE kernel for
focal and the user have confirmed that this resolved the issue (test
build available at ppa:dgadomski/kernel-sf368743).
I am not fully sure what the purpose of this patch was, but I assume
the regression was not intended and the hardware should be still
supported.
Attaching lshw and lspci output.
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