The latest mainline kernel (commit 3f59de0) shows a regression. The symptom is that as soon as the kernel is started, the display is blanked, and it is never turned on again. This problem was bisected to commit f21a21983ef13a031250c4c3f6018e29a549d0f1 ("drm/i915: Splitting intel_dp_detect"). The adapter in question is the integrated graphics controller on a Toshiba Tecra A50 laptop. The output of "lspci -nnv" for that controller is as follows:
00:02.0 VGA compatible controller [0300]: Intel Corporation 4th Gen Core Processor Integrated Graphics Controller [8086:0416] (rev 06) (prog-if 00 [VGA controller]) Subsystem: Toshiba America Info Systems Device [1179:0002] Flags: bus master, fast devsel, latency 0, IRQ 27 Memory at e0000000 (64-bit, non-prefetchable) [size=4M] Memory at d0000000 (64-bit, prefetchable) [size=256M] I/O ports at 4000 [size=64] Expansion ROM at <unassigned> [disabled] Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit- Capabilities: [d0] Power Management version 2 Capabilities: [a4] PCI Advanced Features Kernel driver in use: i915 Kernel modules: i915
New information: I have used SSH to connect to the laptop to see the logs. In the dmesg output, I see "i915 0000:00:02.0: No connectors reported connected with modes". I will try to determine why that is happening.
Larry