Created attachment 137291 [details] output of dmesg We are running Linux on a EMX-SKLUP machine (https://www.avalue.com.tw/Product/Industrial-PC/Industrial-Motherboard/Thin-Mini-ITX/EMX-SKLUP_2521 ) This machine mounts a graphics card: Intel® Skylake U SoC integrated Graphics and we are using the i915 driver to drive two screens, one using the HDMI port and the other using the DisplayPort. We tried different kernels and we noticed the following: 1. Kernel 4.4 all versions work like a charm 2. Kernel 4.9 all versions before 4.9.30 work. All versions after 4.9.40 have problem with the HDMI port. It simply turns out to be always disconnected when issuing an xrandr. Thus, the screen is simply blank. The DisplayPort connection works perfectly. We made some narrowing and the problem seems to have been introduced between the following two commits: • 4.9.30 commit: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?h=linux-4.9.y&id=db3fd4527ed32be44cbd8ffa6dd6a301c89d0d6d • 4.9.40 commit: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?h=linux-4.9.y&id=efcfbfb1d8bf756d1b58fe215bf4e419d176435b • diff of i915 dir: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/diff/drivers/gpu/drm/i915?h=linux-4.9.y&id=db3fd4527ed32be44cbd8ffa6dd6a301c89d0d6d&id2=efcfbfb1d8bf756d1b58fe215bf4e419d176435b 3. All following kernels have the same problem.
Hello Enrico, Could you please attach a clean kern.log(with one boot) or a full dmesg(with boot information) with latest tip https://cgit.freedesktop.org/drm-tip and debug information, drm.debug=0x1e log_bug_len=2M parameters on grub. Also some logs with this information from good and bad commit will be helfpul.
Please try v4.9.81. If that doesn't work, please test the versions between v4.9.30 and v4.9.40 to pinpoint the offending commit. Please provide the full logs (as described by Elizabeth in comment #1) for the working and non-working cases.
Created attachment 137393 [details] dmesg with extended log parameters Here is a full drm-tip dmesg with extended log paramaters.
Fixed by forcing HDMI and DP2 (disabling DP1) at the BIOS level as valid video inputs. The fixed BIOS is XSKLU0GS
Closing, please re-open if still occurs.
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