When i use fbset to set pixclock value 21000 picosecond and it fails: real clock does not exceed 24 MHz. That is because bit 1 of HW_CLKCTRL_CLKSEQ register is set to 0 so ref_xtal is selected to clock lcdif. I need to select ref_pix and enable PIX fractional divider in HW_CLKCTRL_FRAC with setting it`s value. I think its possible to do this by modify .dts file because driver code file drivers/clk/mxs/clk-imx23.c contains string
clks[lcdif_sel] = mxs_clk_mux("lcdif_sel", CLKSEQ, 1, 1, sel_pix, ARRAY_SIZE(sel_pix));
So can anybody show me way how to do this or advice something else?