Created attachment 54728 [details]
dmesg output

Bug description:

When connected (via HDMI) to my Sony Wega TV, the display is normal during POST, the GRUB menu, and the first few seconds of booting the OS.  Shortly after the i915 module is loaded, the screen goes dark with horizontal lines that flicker.  It is not possible to see the console and nothing changes after starting the X server.

System Environment:

-- chipset:  SandyBridge HD 2000 (Core i3-2120T)
-- system architecture:  x86_64
-- xserver-xorg-video-intel:  2.17.0
-- xserver:  X.Org 7.6
-- mesa:  7.11.2
-- libdrm:  2.4.27
-- kernel:  3.1.5
-- Linux distribution:  Debian testing (updated 2011-12-22 17:00)
-- Mobo model:  Intel DH67GD
-- Display connector:  HDMI

Reproducing steps:

1. Connect HTPC to Sony Wega TV via HDMI.
2. Boot computer.

Additional info:
-- If I use the boot parameter 'acpi=off', the video output is fine albeit at the `normal' size of 80x25.

-- Video output from the HTPC is fine when connected (via HDMI) to my LG 246WHX monitor.

-- I have a Dell laptop with a GMA X3100 graphics core (GM965 chipset) and
I am able to successfully use it with the TV.

-- Here's what I get when I query the frame buffer:

# fbset -i

mode "1280x720"
    geometry 1280 720 1280 720 32
    timings 0 0 0 0 0 0 0
    accel true
    rgba 8/16,8/8,8/0,0/0
endmode

Frame buffer device information:
    Name        : inteldrmfb
    Address     : 0xe0063000
    Size        : 3686400
    Type        : PACKED PIXELS
    Visual      : TRUECOLOR
    XPanStep    : 1
    YPanStep    : 1
    YWrapStep   : 0
    LineLength  : 5120
    Accelerator : No

-- If I stick to VESA, I can use the console and the X server albeit at only 640x480@60Hz.