[Intel-gfx] Sandy Bridge Desktop - 1920x1080i interlace not working

[Daniel Vetter]

On Fri, Jan 20, 2012 at 12:37:25AM +0100, Alfonso Fiore wrote:
> On Thu, Jan 19, 2012 at 9:50 PM, Daniel Vetter <daniel at ffwll.ch> wrote:
> >
> > Ok, please make this _really_ precise, we need to know exactly when things
> > work and when not. I presume this was showing a perfect screen over the
> > HDMI cable?
> 
> Yes, I was referring to HDMI. In fact, I was never able to see anything over VGA
> with this MB + CPU (I never tried VGA with H55 + i3 550 cause HDMI worked
> but I used VGA from my laptop with the same cable and the same TV).
> Interestingly, I can always see BIOS and BIOS menu over HDMI
> but when I connect only VGA I can't see anything also at the BIOS level.
> So maybe the VGA problem has nothing to do with the driver?
> [I was wrong, I managed to see something over VGA during these tests]
> 
> I'll try to be as precise as I can.
> 
> so I created a little script that I will run at each test.
> 
> $ cat run_me.sh
> #!/bin/bash
> WHEN="`date +%Y%m%d_%H%M%S`"
> xrandr -q > ./xrand-q.$WHEN.output
> xrandr --verbose > ./xrand--verbose.$WHEN.output
> dmesg > ./dmesg.$WHEN.output
> cp /var/log/Xorg.0.log ./Xorg.0.$WHEN.output
> cp /sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-VGA-1/edid
> ./EDID_VGA.$WHEN.output
> cp /sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-HDMI-A-2/edid
> ./EDID_HDMI.$WHEN.output
> $HOME/test_GPU/intel_gpu_tools/intel-gpu-tools-1.1/tools/intel_reg_dumper
> > ./intel_reg_dumper.$WHEN.output
> 
> And attached you can find the whole tgz. Here I simply walk you
> through my tests.
> 
> TEST-01
> ========
> Only VGA (DVI-I) connected.
> Changing TV source to VGA.
> Reboot.
> Nothing shows on the screen (not even BIOS).
> But LightDM started (I can connect with VNC).
> FOLDER=VGA_cable_VGA_source_1024_768
> 
> TEST-02
> ========
> NO reboot
> NO cable change (Only VGA (DVI-I) connected and TV source to VGA)
> xrandr --output VGA1 --mode 800x600 (from VNC)
> well... amazing. I can see the screen. I get no overscan left/right
> but a bit up/down
> FOLDER=VGA_cable_VGA_source_800_600

Ok, from the above it looks like the VGA input on your TV is dirt-cheap
and it barely manages to sync at 800x600 and fails already at 1024x768 -
not even the bios manages to put a picture on your TV :(

To make sure that this is not an issue with the intel gpu, can you maybe
test the vga input with another machine with different gpu?

> TEST-03
> ========
> connecting both VGA and HDMI
> reboot
> TV source still on VGA so I don't see anything (blue screen)
> connecting over VNC I can see screen is 1024x768
> FOLDER=VGA_HDMI_cables_VGA_source_1024x768
> 
> TEST-04
> ========
> NO reboot
> NO cable change
> NO TV source change
> xrandr --output VGA1 --mode 800x600 (from VNC)
> the screen goes from blue to the actual desktop,
> but the TV shows 800x600 while the resolution stays at 1024x768
> so there is huge overscan at bottom and right plus a bit on the top.
> FOLDER=VGA_HDMI_cables_VGA_source_800x600

The overscan is expected because your other output HDMI is still at
1024x768 and hence your desktop is large enough to fit both.

See the first line starting with "Screen 0:" in the xrandr output for
current the size of your desktop.

> since you said "Please ensure that you use the same resolution for both"
> (but I have a feeling I didn't understand you)
> I'll put this back to 1024x768 before running tests on HDMI
> xrandr --output VGA1 --mode 1024x768 (from VNC)
> the screen goes back to blue
> 
> TEST-05
> ========
> NO reboot
> NO cable change
> TV source change from TV to HDMI
> the screen is as expected perfect with not a pixel of overscan
> FOLDER=VGA_HDMI_cables_HDMI_source_1024x768
> 
> TEST-06
> ========
> NO reboot
> NO cable change
> NO TV source change
> xrandr --output HDMI2 --mode 1280x720 (from VNC)
> the screen shows but with overscan on all four edges
> FOLDER=VGA_HDMI_cables_HDMI_source_1280x720
> 
> TEST-07
> ========
> NO reboot
> NO cable change
> NO TV source change
> xrandr --output HDMI2 --mode 800x600 (from VNC)
> this is similar to what happened over VGA:
> the desktop stays 1024x768 but the TV only shows 800x600
> so huge overscan bottom and right
> FOLDER=VGA_HDMI_cables_HDMI_source_800x600

Same as above I suspect.

> when I removed the VGA cable for the next tests the screen
> automatically switched to 1024x768
> I run the script again just in case it gives you some good info:
> FOLDER=HDMI_cable_HDMI_source_1024x768_after_disconnect_VGA
> 
> TEST-08
> ========
> connecting only HDMI
> reboot
> login screen is "weird" (I sent the photo already)
> Ah, I didn't realize this earlier! From VNC I see that
> lightDM is running at 1280x720 when it looks "weird"
> when I type my password the screen goes to 1024x768 and now it's black
> (used to be cut in half)
> FOLDER=HDMI_cable_HDMI_source_1024x768
> 
> TEST-09
> ========
> NO reboot
> NO cable change
> NO TV source change
> xrandr --output HDMI2 --mode 1280x720 (from VNC)
> weird! The screen stays black (so it doesn't look like the login screen)
> the desktop (from VNC) correctly resizes to 1280x720
> FOLDER=HDMI_cable_HDMI_source_1280x720
> 
> TEST-10
> ========
> NO reboot
> NO cable change
> NO TV source change
> xrandr --output HDMI2 --mode 800x600 (from VNC)
> black screen
> the desktop (from VNC) correctly resizes to 800x600
> FOLDER=HDMI_cable_HDMI_source_800x600
> 
> I believe I follow your instructions on what info to give you.

Yep, excellent test descriptions! I still need to look at the register
dumps, but I think another test might be useful:

Only HDMI with nomodeset, then again grab the intel_reg_dump. Iirc that
works, so it could be useful to see how the bios sets things up with just
the hdmi cable.

Yours, Daniel
-- 
Daniel Vetter
Mail: daniel at ffwll.ch
Mobile: +41 (0)79 365 57 48