Re: Sandy Bridge Desktop - 1920x1080i interlace not working

[Daniel Vetter <daniel@ffwll.ch>]

On Sat, Jan 21, 2012 at 10:09:16PM +0100, Daniel Vetter wrote:
> 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@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?

Another thing to try with VGA is whether the higher refresh-rate helps.
You can select that with --rate, i.e.

xrandr --output VGA1 --mode 1024x768 --rate 60.0

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