gma500: wrong pixel clock on LVDS (half the correct frequency)
pmarques at masterguardian.com
Wed May 7 20:21:07 PDT 2014
I have a embedded PC system here that has an Atom Z510. The system
includes a GMA500 graphics chip.
The display is connected through the LVDS port and has a resolution of
The system works ok in Windows and painfully slowly in Linux with the
vesa driver, but without any flicker.
Using the gma500 driver, the pixel clock seems to be half of what it
should be (measured with an oscilloscope). When the image is good the
pixel clock is around 65MHz. When the gma500 driver sets the resolution
the pixel clock goes to around 32MHz. This gives a frame rate of around
30Hz which explains the horrible screen flicker. The performance is
quite good, though.
I tried running xrandr to create new modes, but the pixel clock is
always wrong, no matter what I tried.
The kernel version is 3.12.1. I looked at the git repository log to see
if anything changed in the meanwhile that could affect this, but nothing
Can you give me some pointers to what I should try next? Some obscure
kernel parameter? Do you need more information?
The linux graphics system changed a bit over the last few years (KMS,
etc.) and I missed some of the changes, so please bare with me if I ask
Thanks in advance for any help,
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