It is a requirement of my HDMI display (it is the LG LP097X02) that pixel clock should be 100.3MHz.
If I connect the display to the BBB with HDMI cable, there is no image, nor a backlight.
The root of the problem (to my understanding) is that the driver sets the LCD_CTRL register to a value of 0x101.
The last was verified using devmem2:
root@beaglebone:~# ./devmem2 0x4830e004
Memory mapped at address 0xb6ff8000.
Value at address 0x4830E004 (0xb6ff8004): 0x101
But this value is illegal for the Sitara processor: the clk divisor should be “2” minimum for raster mode.
(TRM, clause 220.127.116.11)
Is there a workaround so that to set the pixel clock to 100.3MHz (the resolution I need is 1024x768 @60Hz)?
The BBB documentation lists max frequency of 170MHz. Here in the forum there are words that maximum is 125 MHz but audio should be disabled.
I do not care about audio.
If I manually set the resolution (using cvt and xrandr) to 1024x768 with any lower pixel clock, the backlight turns On, and I there is a pixel clock on the BBB HDMI converter TDa19988, pin4.
If I set the screen format to the default (EDID) 100.3 MHz value, there is no clock on the TDA19988, pin4.
(Also, I’m wondering, why if setting the LCD_CTRL to an illegal value, the xrandr does not print any warning message)
I use (hopefully latest) Linux 3.8.13 armv7, Angstrom Cloud9 GNOME Image 2013.09.04