i915: regression: after DP connected monitor is turned off, when turned on, it does not work anymore

[Jiri Pirko]

Hi.

I'm experiencing this issue on Fedora kernel, but I tested that upstream
kernel behaves the same.

Description of problem:

On my T440s machine I'm experiencing this regression when if I turn off
DP connected display, I can never make graphics work again.

Version-Release number of selected component (if applicable):
3.17.6-200.fc20.x86_64

How reproducible:
always

Steps to Reproduce:
1. have DP connected display
2. turn it off
3. turn it on

Actual results:
No signal in display.

Expected results:
There's signal going into display, everything is flooded in colours.

Additional info:
With 3.16.4-200.fc20.x86_64 this is working without any issues.
I tested with current Linus's git (58628a7831edac5f7a13) and the issue is
still there.

00:02.0 0300: 8086:0a16 (rev 0b) (prog-if 00 [VGA controller])
        Subsystem: 17aa:220c
        Flags: bus master, fast devsel, latency 0, IRQ 60
        Memory at f0000000 (64-bit, non-prefetchable) [size=4M]
        Memory at e0000000 (64-bit, prefetchable) [size=256M]
        I/O ports at 3000 [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

Screen 0: minimum 320 x 200, current 1920 x 1200, maximum 8192 x 8192
eDP-0 connected (normal left inverted right x axis y axis)
   1920x1080     60.01 +
   1400x1050     59.98  
   1280x1024     60.02  
   1280x960      60.00  
   1024x768      60.00  
   800x600       60.32    56.25  
   640x480       59.94  
DP-0 disconnected (normal left inverted right x axis y axis)
HDMI-0 disconnected (normal left inverted right x axis y axis)
DP-1 connected primary 1920x1200+0+0 (normal left inverted right x axis y axis) 518mm x 324mm
   1920x1200     59.95*+
   1920x1080     60.00    50.00    59.94  
   1920x1080i    60.00    50.00    59.94  
   1600x1200     60.00  
   1680x1050     59.95  
   1280x1024     60.02  
   1440x900      59.89  
   1280x960      60.00  
   1280x720      60.00    50.00    59.94  
   1024x768      60.00  
   800x600       60.32  
   720x576       50.00  
   720x480       60.00    59.94  
   640x480       60.00    59.94  
HDMI-1 disconnected (normal left inverted right x axis y axis)


Please let me know if you need me to provide any other info. I'm eager to
test patches.

Thanks!

Jiri