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grant123
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PostPosted: Mon Mar 31, 2014 8:34 pm    Post subject: Force resolution Reply with quote

How can I force X to use a certain resolution when it doesn't detect the attached TV as being capable of that resolution?
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NeddySeagoon
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PostPosted: Mon Mar 31, 2014 9:35 pm    Post subject: Reply with quote

grant123,

That depends on the driver you are using.

You will need a modeline. That link tells you what its all about.
Its a PITA working out the numbers with a calculator but this link will generate some numbers for you.
That much is common.

The driver specific part is how you tell the driver you really do know better than the EDID.
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Computer users fall into two groups:-
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grant123
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PostPosted: Mon Mar 31, 2014 10:48 pm    Post subject: Reply with quote

That could be a problem. I'm using the omapfb driver which isn't exactly packed with features.

I set up the 1360x768 modeline in xorg.conf but I get:

Code:
[    24.055] (II) omapfb(0): Not using mode "1360x768" (height too large for virtual size)
[    24.056] (II) omapfb(0): Printing probed modes for output LCD
[    24.056] (II) omapfb(0): Modeline "640x480"x59.5   23.50  640 688 720 800  480 483 487 494 (29.4 kHz P)
[    24.056] (II) omapfb(0): Output LCD connected
[    24.056] (II) omapfb(0): Using exact sizes for initial modes
[    24.056] (II) omapfb(0): Output LCD using initial mode 640x480
[    24.058] (II) omapfb(0): Using default gamma of (1.0, 1.0, 1.0) unless otherwise stated.
[    24.058] (II) omapfb(0): XRandR extension initialized
[    24.058] (--) omapfb(0): Virtual size is 640x480 (pitch 640)
[    24.059] (**) omapfb(0):  Mode "640x480": 23.5 MHz, 29.4 kHz, 59.5 Hz
[    24.059] (II) omapfb(0): Modeline "640x480"x59.5   23.50  640 688 720 800  480 483 487 494 (29.4 kHz P)
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NeddySeagoon
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PostPosted: Tue Apr 01, 2014 6:47 pm    Post subject: Reply with quote

grant123,

Code:
[    24.056] (II) omapfb(0): Modeline "640x480"x59.5   23.50  640 688 720 800  480 483 487 494 (29.4 kHz P)
...
[    24.058] (--) omapfb(0): Virtual size is 640x480 (pitch 640) 
Is standard VGA, which is what grub uses.

What does
Code:
man omapfb
tell you on your ARM board?
Its also possible that you need to allocate the framebuffer more RAM so it can hold larger images.
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Computer users fall into two groups:-
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grant123
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PostPosted: Wed Apr 02, 2014 1:56 pm    Post subject: Reply with quote

There is no man entry for omapfb unfortunately. I googled but didn't come up with anything.

I tried increasing RAM for both framebuffers but the result is the same.

The weird thing is omapfb will go through a certain amount of time detecting the TV's native resolution correctly at 1360x768 and choosing it automatically at boot every time. Then it will go through a period of time when it's 640x480 at every boot. Then 1360x768 for a while. This last time it switched, I'm sure I didn't change anything. What could cause that kind of inconsistency?
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grant123
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PostPosted: Wed Apr 09, 2014 1:00 am    Post subject: Reply with quote

It just switched back to 1360x768 after my latest reboot and I noticed that this resolution is displayed in a notification window in the corner of the screen by the TV when the system first starts booting, long before X starts. Lately 640x480 has been the resolution displayed in that notification window. So it seems like the system or TV "decides" which resolution it will display very early in the boot process.
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