i.MX6ULL pixel clock can't follow device tree setting ?

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i.MX6ULL pixel clock can't follow device tree setting ?

307 Views
Danube
Contributor IV

We want to set i.MX6ULL output 800x600-60 VESA timing.

We use 4.1.15_1.1.0 BSP version

My device tree display timing is

display0: display {
        bits-per-pixel = <16>;
        bus-width = <24>;

display-timings {
            native-mode = <&timing0>;
            
            timing0: timing0 {
                clock-frequency = <40000000>;
                hactive = <800>;
                vactive = <600>;
                hback-porch = <88>;
                hfront-porch = <40>;
                vback-porch = <23>;
                vfront-porch = <1>;
                hsync-len = <128>;
                vsync-len = <4>;

                de-active = <1>;
                hsync-active = <1>;
                vsync-active = <1>;
                pixelclk-active = <0>;
            };
        };
    };
       

and lcdif_sel is select pll5

I also check clock tree information.

   pll5_bypass_src                       1            1    24000000          0 0
       pll5                               1            1   649515096          0 0
          pll5_bypass                     1            1   649515096          0 0
             pll5_video                   1            1   649515096          0 0
                pll5_post_div             1            1   324757548          0 0
                   pll5_video_div           1            1   324757548          0 0
                      lcdif_pre_sel           1            1   324757548          0 0
                         lcdif_pred           1            1   108252516          0 0
                            lcdif_podf           1            1    36084172          0 0
                               lcdif_pix           1            1    36084172          0 0
                               iomuxc           0            0    36084172          0 0
                               lcdif_sel           0            0    36084172          0 0

And We also check waveform from scope , clock is 36.27M

40MHz_pixel_clock.jpg

How to let lcdif_sel out 40MHz ?

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52 Views
igorpadykov
NXP TechSupport
NXP TechSupport

Hi Appolo

one can try to set pll5 (which is currently = 649515096) to other frequency

so it could be divided to produce 40MHz. One can printf ccm registers

following Figure 18-2. Clock Tree i.MX6ULL RM

http://www.nxp.com/docs/en/reference-manual/IMX6ULLRM.pdf 

Also may be useful try to change clock sources using example on

IMX6Q Device Tree Binding for ADV7343 Encoder 

Best regards
igor
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52 Views
Danube
Contributor IV

Hi Sir,

As I understand ,i.MX6Q/D/DL/SOLO can reference device tree "clock-frequency" to output currect pixel clock if we use pll5.

Does mxsfb.c don't reference  "clock-frequency" ?

OR

If I need to setting VESA timing *640x480-60 ,800x600-60" , I need to add PLL5=fixed clock into C file ?

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