This is a workaround for what I think is a bug in the 2700G chip. The PLL output frequency is adustable using 3 values (M, N and P. See code for formula). The N value range is documented to be 1 to 7 but when it is set to 1, the output frequency is lower than it should be (divided by 2), giving unexpected results such as no sync on a CRT display. This patch prevents N=1 when searching for the best value for the requested pixclock. Signed-off-by: Raphael Assenat --- linux-2.6.18-rc2/drivers/video/mbx/mbxfb.c 2006-07-17 15:20:06.000000000 -0400 +++ linux-2.6.18-rc2-8d/drivers/video/mbx/mbxfb.c 2006-08-14 14:04:39.000000000 -0400 @@ -118,8 +118,19 @@ /* convert pixclock to KHz */ pixclock = PICOS2KHZ(pixclock_ps); + /* PLL output freq = (ref_clk * M) / (N * 2^P) + * + * M: 1 to 63 + * N: 1 to 7 + * P: 0 to 7 + */ + + /* RAPH: When N==1, the resulting pixel clock appears to + * get divided by 2. Preventing N=1 by starting the following + * loop at 2 prevents this. Is this a bug with my chip + * revision or something I dont understand? */ for (m = 1; m < 64; m++) { - for (n = 1; n < 8; n++) { + for (n = 2; n < 8; n++) { for (p = 0; p < 8; p++) { clk = (ref_clk * m) / (n * (1 << p)); err = (clk > pixclock) ? (clk - pixclock) :