i.MX6 - Yocto GUI with 24bpp display

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i.MX6 - Yocto GUI with 24bpp display

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Ansari
Contributor IV

Hi,

We are using imx6Q custom platform for our development which is based on sabresd platform.

We are using Linux 3.14.28_1.0.0-GA BSP for our development.

Our primary display is connected with LVDS0. The pixel format is RGB24 and bpp is 24. Here we are able to get the yocto GUI properly.

Then we tried to dump a raw picture (cat red.raw > /dev/fb0) on the display. But the LCD is not displaying the exact image. 

We found that the Yocto GUI changes the display format to 16bpp. Please find the fbset values in below and the bpp is set to 16bpp here.

fbset

mode "1024x768-53"

    # D: 56.883 MHz, H: 42.324 kHz, V: 52.511 Hz

    geometry 1024 768 1024 768 16

    timings 17580 160 24 29 3 136 6

    rgba 5/11,6/5,5/0,0/0

endmode

Later, we have forced the display bpp into 24 bpp by below command.  In this case, the Yocto GUI is not proper but the raw picture is proper format.

fbset -fb /dev/fb0 -depth 24

We want the Yocto GUI in 24bpp format so that we can dump the raw picture in proper format and proper Yocto GUI in 24bpp.

Please suggest us.

Thank You,

Regards,

Ansari

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alejandrolozan1
NXP Employee
NXP Employee

Hi,

Have you checked that the device tree has the correct settings in the ldb node?

for example:

ldb: ldb@53fa8008 {

        #address-cells = <1>;

        #size-cells = <0>;

        compatible = "fsl,imx53-ldb";

        gpr = <&gpr>;

        clocks = <&clks 122>, <&clks 120>,

                 <&clks 115>, <&clks 116>,

                 <&clks 123>, <&clks 85>;

        clock-names = "di0_pll", "di1_pll",

                      "di0_sel", "di1_sel",

                      "di0", "di1";

        lvds-channel@0 {

                reg = <0>;

                crtcs = <&ipu 0>;

                fsl,data-mapping = "spwg";

                fsl,data-width = <24>;

                display-timings {

                        /* ... */

                };

        };

/Alejandro

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Ansari
Contributor IV

Dear Alejandro,

We have done this "fsl,data-width=24" as well as "fsl,data-width=18" settings.  After this test case only we have raised this Query.

Please find below device tree.

    mxcfb1: fb@0 {
            compatible = "fsl,mxc_sdc_fb";
            disp_dev = "ldb";
            interface_pix_fmt = "RGB24";
            default_bpp = <24>;
            int_clk = <0>;
            late_init = <0>;
            status = "disabled";
    };

&ldb {

        status = "okay";

        lvds-channel@0 {

                fsl,data-mapping = "spwg";

                fsl,data-width = <24>;

                primary;

                crtc = "ipu1-di0";

                status = "okay";

                display-timings {

                        native-mode = <&timing0>;

                        timing0: ldb-wvga {

                                clock-frequency = <56880000>;

                                hactive = <1024>;

                                vactive = <768>;

                                hback-porch = <160>;

                                hfront-porch = <24>;

                                vback-porch = <29>;

                                vfront-porch = <3>;

                                hsync-len = <136>;

                                vsync-len = <6>;

                        };

                };

        };

};

Please suggest us to fix this issue.

Regards,

Ansari

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