Weird framebuffer bug?

Weird framebuffer bug?

[grfgguvf.29601511]

Hi,

I am having a really strange bug where every fifth or so vertical line
is not displayed when running X using the framebuffer (so the right fifth
of the screen is also left black). And it's not the monitor settings. If the
image is stretched to fill the screen the lines are still omitted (It's an
LCD and it interpolates the lines so the whole image looks blurred).

However,
when taking a screenshot and later viewing with correct display, everything
looks OK on it.

Text mode on the framebuffer is OK, the whole screen is
filled. X using the video card directly is also OK.

Maybe this is an X
bug if yes then sorry for reporting at the wrong place.

Software used:

* Linux kernel 2.6.16, the binary version from Debian for 686
* vesafb framebuffer
driver as shipped with the kernel, loaded from module
* X11R7 Xorg server
1.0, again the Debian binary
* fbdev X driver as shipped with Xorg
* [nv
X driver (non-accelerated) when using X directly on the card]

The framebuffer
and X with both drivers is set to 24bit color mode.

Hardware:
* NVidia
GeForce 2, on AGP
* Samsung TFT LCD connected on a VGA cable
* [x86 machine]


Anyone else experienced a similar bug or know what can it be? I tried searching
around but nothing relevant.

Re: Weird framebuffer bug?

[Valdis.Kletnieks]

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On Thu, 04 May 2006 21:24:53 -0000, grfgguvf.29601511@bloglines.com said:
> I am having a really strange bug where every fifth or so vertical line
> is not displayed when running X using the framebuffer (so the right fifth
> of the screen is also left black). And it's not the monitor settings. If the
> image is stretched to fill the screen the lines are still omitted (It's an
> LCD and it interpolates the lines so the whole image looks blurred).

I'll bite.  Have you tried using a configuration that specifies the *actual*
LCD resolution so it doesn't have to interpolate?  It could be that the
interpolation hardware is buggy.

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Re: Weird framebuffer bug?

[grfgguvf.29601511]

--- Valdis.Kletnieks@vt.edu wrote:
> I'll bite.  Have you tried using a configuration
that specifies the *actual*
> LCD resolution so it doesn't have to interpolate?
 It could be that the
> interpolation hardware is buggy.

Both vesafb and
X (with fbdev and nv too) are set to 1024x768 which is the actual resolution.

Re: Weird framebuffer bug?

[Antonino A. Daplas]

Valdis.Kletnieks@vt.edu wrote:
> On Thu, 04 May 2006 21:24:53 -0000, grfgguvf.29601511@bloglines.com said:
>> I am having a really strange bug where every fifth or so vertical line
>> is not displayed when running X using the framebuffer (so the right fifth
>> of the screen is also left black). And it's not the monitor settings. If the
>> image is stretched to fill the screen the lines are still omitted (It's an
>> LCD and it interpolates the lines so the whole image looks blurred).
> 
> I'll bite.  Have you tried using a configuration that specifies the *actual*
> LCD resolution so it doesn't have to interpolate?

And if you can't specify the actual resolution with vesafb, try nvidiafb.

Tony

Re: Weird framebuffer bug?

[grfgguvf.29601511]

--- Antonino A. Daplas <adaplas@gmail.com> wrote:
> And if you can't specify
the actual resolution with vesafb, try nvidiafb.

I have specified the actual
resolution. Text mode with vesafb fills the whole screen (and the on-screen
menu says 1024x768 which is the native resolution of the monitor). The screenshot
I took when using X via fbdev (set to 1024x768 too) while the displaying was
erroneous is 1024x768 as well. It somehow just doesn't reach the monitor in
that form.

Re: Weird framebuffer bug?

[Antonino A. Daplas]

grfgguvf.29601511@bloglines.com wrote:
> --- Antonino A. Daplas <adaplas@gmail.com> wrote:
> 
>> And if you can't specify
> the actual resolution with vesafb, try nvidiafb.
> 
> 
> 
> I have specified the actual
> resolution. Text mode with vesafb fills the whole screen (and the on-screen
> menu says 1024x768 which is the native resolution of the monitor). The screenshot
> I took when using X via fbdev (set to 1024x768 too) while the displaying was
> erroneous is 1024x768 as well. It somehow just doesn't reach the monitor in
> that form.
> 

Does the same thing happens with different color depths?

Can you try using the "vesa" driver with X?  If the same thing happens, it might
be a problem with the BIOS.

BTW, what does dmesg and fbset -i say?

Tony

PS: I'll be traveling in a few hours, so I may not be able to answer back.

Re: Weird framebuffer bug?

[grfgguvf.29601511]

--- Antonino A. Daplas <adaplas@gmail.com> wrote:
> Does the same thing happens
with different color depths?
> 
> Can you try using the "vesa" driver with
X?  If the same thing happens, it might
> be a problem with the BIOS.
>


I will check these later.

> 
> BTW, what does dmesg and fbset -i say?

>

% dmesg | egrep -i 'frame|fb|vesa|nv'
 BIOS-e820: 0000000007fff000
- 0000000008000000 (ACPI NVS)
Security Framework v1.0.0 initialized
vesafb:
framebuffer at 0xf0000000, mapped to 0xb8880000, using 6144k, total 32768k

vesafb: mode is 1024x768x32, linelength=4096, pages=1
vesafb: protected
mode interface info at c000:c060
vesafb: scrolling: redraw
vesafb: Truecolor:
size=8:8:8:8, shift=24:16:8:0
Console: switching to colour frame buffer device
128x48
fb0: VESA VGA frame buffer device

# fbset -i

mode "1024x768-76"

    # D: 78.653 MHz, H: 59.949 kHz, V: 75.694 Hz
    geometry 1024 768 1024
768 32
    timings 12714 128 32 16 4 128 4
    rgba 8/16,8/8,8/0,8/24
endmode


Frame buffer device information:
    Name        : VESA VGA
    Address
    : 0xf0000000
    Size        : 6291456
    Type        : PACKED PIXELS

    Visual      : TRUECOLOR
    XPanStep    : 0
    YPanStep    : 0
 
  YWrapStep   : 0
    LineLength  : 4096
    Accelerator : No


> Tony

> 
> PS: I'll be traveling in a few hours, so I may not be able to answer
back.
> 

Well thank you for answering so far then.
This is not urgent
you can answer tomorrow or at any later time.

Re: Weird framebuffer bug?

[grfgguvf.29601511]

--- Antonino A. Daplas <adaplas@gmail.com> wrote:
> Does the same thing happens
with different
> color depths?

That was it. With mode vga=0x318 (1024x768
"16m
colours") no matter what colour depth I set X to
the display will be
incorrect. Set to 24bits every
4th (not 5th, that was my bad estimation)
vertical
line is omitted. This is because the framebuffer
is really using
32bits/pixel.

Using mode vga=0x317 (1024x768 "64k colours")
and X set
to 16bits colour depth everything is OK.

This is really an X fbdev driver
problem... It
should use 32bits/pixel by padding the last byte.
I will write
Xorg about this.

> Can you try using the "vesa" driver with X?  If
> the
same thing happens, it might
> be a problem with the BIOS.

[I tried this
first, and as expected X's vesa
driver works.]

Thanks Antonino!