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imx6ull RGB lcd display issue

Question asked by luke li on Feb 3, 2018
Latest reply on Feb 22, 2018 by luke li

Dear sir:

         we are using imx6ull yocto platform for our project. we encounter a lcd display issue.

         we are using 480x320 RGB lcd. the display seems fine in uboot, but the not perfect in kernel. we have checked with LCD FAE,  our configuration are correct. we suspect it may related to platform. 

 

hardware connection:

         18 bit bus width which connect to LCD_DATA0--LCD_DATA17. enclosed hardware_connection.png in the attachment.

 

configuration in uboot, kernel:

uboot configuration:

struct display_info_t const displays[] = {{

        .bus = MX6UL_LCDIF1_BASE_ADDR,

        .addr = 0,

        .pixfmt = 18,

        .detect = NULL,

        .enable = do_enable_parallel_lcd,

        .mode   = { 

                .name                   = "EDC3507C21",

                .xres           = 320,

                .yres           = 480,

                .pixclock       = 108695,

                .left_margin    = 5,

                .right_margin   = 5,

                .upper_margin   = 2,

                .lower_margin   = 2,

                .hsync_len      = 5,

                .vsync_len      = 2,

                .sync           = 0,

                .vmode          = FB_VMODE_NONINTERLACED

} } };

kernel configuration:

&lcdif {

        pinctrl-names = "default";

        pinctrl-0 = <&pinctrl_lcdif_dat

                     &pinctrl_lcdif_ctrl

                     &pinctrl_lcdif_reset>;

        display = <&display0>;

        status = "okay";

 

        display0: display {

                bits-per-pixel = <32>;

                bus-width = <18>;

 

                display-timings {

                        native-mode = <&timing0>;

                        timing0: timing0 {

                        clock-frequency = <9200000>;

                        hactive = <320>;

                        vactive = <480>;

                        hfront-porch = <5>;

                        hback-porch = <5>;

                        hsync-len = <5>;

                        vback-porch = <2>;

                        vfront-porch = <2>;

                        vsync-len = <2>;

 

                        hsync-active = <0>;

                        vsync-active = <0>;

                        de-active = <1>;

                        pixelclk-active = <0>;

                        }; 

                }; 

        }; 

};

 

result :

 for uboot. enclosed uboot.bmp, lcd_uboot.jpg.  

  the picture uboot.bmp display well during uboot(lcd_uboot.jpg).

 

 for kernel. enclosed kernel.jpg, lcd_kernel.jpg.

 the picture kernel.jpg NOT display perfect during kernel(lcd_kernel.jpg).

 the horizontal line is correct, but the vertical line NOT display correct.

 

I also enclose the result about LCD UI display. ui.png is the frame buffer ,lcd_ui.png lcd_ui_zoom.jpg  are the lcd display result. you can see the display not well.

 

question:

 the same configuration works in uboot well, but not display well in kernel. 

can you give us any suggestion about why this issue happens?

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