Re: i945G 1280x768 sync polarity bug

Barry Scott wrote:
> Using the Xfree86 4.6.0 i810 driver I'm seeing a problem with sync 
> polarity setting.
>
> This modeline is required for 1280x768 mode:
>
> Modeline "1280x768"   79.30  1280 1335 1473 1665  768 769 772 793 
> -hsync +vsync
>
> But the syncs, as shown on an oscilloscope are +hsync +vsync.
>
> I added debug messages to show the Flags used. And here is a section 
> of the log:
>
> (II) I810(0): Not using built-in mode "1280x1024" (height too large 
> for virtual size)
> (II) I810(0): Not using built-in mode "1360x768" (width too large for 
> virtual size)
> (II) I810(0): Increasing the scanline pitch to allow tiling mode (1280 
> -> 2048).
> (--) I810(0): Virtual size is 1280x768 (pitch 2048)
> (**) I810(0): *Built-in mode "1280x768"
> (**) I810(0):  Built-in mode "1024x768"
> (**) I810(0):  Built-in mode "800x600"
> (**) I810(0):  Built-in mode "640x480"
> (II) I810(0): Attempting to use 60.06Hz refresh for mode "1280x768" (85a)
> (II) I810(0): I830SetModeParameters() Flags pMode->Flags 0x6 
> block->Flags 0x4
> (II) I810(0): Attempting to use 75.08Hz refresh for mode "1024x768" (854)
> (II) I810(0): I830SetModeParameters() Flags pMode->Flags 0x5 
> block->Flags 0x0
> (II) I810(0): Attempting to use 75.00Hz refresh for mode "800x600" (852)
> (II) I810(0): I830SetModeParameters() Flags pMode->Flags 0x5 
> block->Flags 0x0
> (II) I810(0): Attempting to use 75.00Hz refresh for mode "640x480" (850)
> (II) I810(0): I830SetModeParameters() Flags pMode->Flags 0xa 
> block->Flags 0xc
>
> This shows that the I830SetModeParameters() has the correct values in 
> but pMode-Flags
> and block->Flags.
>
> I have also tested other modes as listed here
>
> Mode        Flags   Syncs on wire
> 640x480    0xC     -hsync -vsync
> 800x600    0x0     +hsync +vsync
> 1024x768    0xC     -hsync -vsync
> 1280x1024   0x0     +hsync +vsync
> 1280x768    0x4     +hsync +vsync
>
> As you can see all the Syncs track the Flags except 1280x768.
>
> Looking at the VBE code it seems that as long as the Flags are
> defined correctly by the driver then its down to the INT10 BIOS
> to set the syncs on the hardware.
>
> Do you think this is a BIOS bug or a driver bug?
>
> Barry
I've just noticed that the refresh rate is 52.73Hz not 60Hz as expected.
Clearly the mode is not being honored.

Barry