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AM623: RGB888 display blurry screen

Part Number: AM623

Tool/software:

Hi, Ti

When I display solid color pictures, the LCD display is normal, when I display complex pictures, a blurry screen occurs.

  • Hi,

    How are you displaying the picture? Is it Linux or RTOS? What frameworks are you using?

    Regards,
    Krunal

  • I use Linux to display the picture, the display driver is tidss, the panel driver is simple-panel.c. And I use libjpeg to display these jpg images.

  • Do you see similar behavior with Qt+Weston or Gstreamer? I am trying to isolate if the issue is with libjpeg or DSS setting.

    Regards,
    Krunal

  • Hi Krunal,

    I use QT4.8.6+qws to display, it has similar behavior.

  • Hi,

    What SDK baseline are you on and what changes have you made to your DT files? Also, have you probed the clocks and the data lines to ensure everything is latching on rising edge or falling edge and lcd timing are based on your LCD specs.

    Regards,
    Krunal

  • Hi,

    1. The sdk is ti-processor-sdk-linux-am62xx-evm-09.02.01.10, the kernel source code is ti-linux-kernel-6.1.83

    2. The changes to the DT file are as follows:

    / {
    	backlight_rgb: backlight-rgb {
    		compatible = "pwm-backlight";
    		pwms = <&epwm1 0 20000 0>;
    		brightness-levels = <
    			0  20  20  21  21  22  22  23
    			23  24  24  25  25  26  26  27
    			27  28  28  29  29  30  30  31
    			31  32  32  33  33  34  34  35
    			35  36  36  37  37  38  38  39
    			40  41  42  43  44  45  46  47
    			48  49  50  51  52  53  54  55
    			56  57  58  59  60  61  62  63
    			64  65  66  67  68  69  70  71
    			72  73  74  75  76  77  78  79
    			80  81  82  83  84  85  86  87
    			88  89  90  91  92  93  94  95
    			96  97  98  99 100 101 102 103
    			104 105 106 107 108 109 110 111
    			112 113 114 115 116 117 118 119
    			120 121 122 123 124 125 126 127
    			128 129 130 131 132 133 134 135
    			136 137 138 139 140 141 142 143
    			144 145 146 147 148 149 150 151
    			152 153 154 155 156 157 158 159
    			160 161 162 163 164 165 166 167
    			168 169 170 171 172 173 174 175
    			176 177 178 179 180 181 182 183
    			184 185 186 187 188 189 190 191
    			192 193 194 195 196 197 198 199
    			200 201 202 203 204 205 206 207
    			208 209 210 211 212 213 214 215
    			216 217 218 219 220 221 222 223
    			224 225 226 227 228 229 230 231
    			232 233 234 235 236 237 238 239
    			240 241 242 243 244 245 246 247
    			248 249 250 251 252 253 254 255
    		>;
    		power-supply = <&vdd_pwm>;
    		default-brightness-level = <200>;
    		is-forlinx;
    		status = "okay";
    	};
    	
    	panel_rgb: panel-rgb {
    		compatible = "name,lcd-rgb", "panel-dpi";
    		backlight = <&backlight_rgb>;
    		status = "okay";
    		pinctrl-names = "default";
    		pinctrl-0 = <&lcd_crtl_pins_default>;
    		enable-gpios = <&main_gpio0 43 GPIO_ACTIVE_HIGH>;
    
    		port {
    				rgb_in0: endpoint {
    					remote-endpoint = <&dpi1_out>;
    				};
    		};
    	};
    };
    
    &dss_ports {
    	#address-cells = <1>;
    	#size-cells = <0>;
    
    	port@1 {
    		reg = <1>;
    
    		dpi1_out: endpoint {
    			remote-endpoint = <&rgb_in0>;
    		};
    	};
    };
    
    &epwm1 {
    	pinctrl-names = "default";
    	pinctrl-0 = <&main_epwm1_a_pins_default>;
    	status  = "okay";
    };
    
    &dss {
    	pinctrl-names = "default";
    	pinctrl-0 = <&main_dss0_pins_default>;
    	status  = "okay";
    };

    3. The changes to the panel-simple.c are as follows:

    static const struct drm_display_mode name_mode = {
    		.clock = 51200,
    		.hdisplay = 1024,
    		.hsync_start = 1024 + 160,
    		.hsync_end = 1024 + 160 + 10,
    		.htotal = 1024 + 160 + 10 + 160,
    		.vdisplay = 600,
    		.vsync_start = 600 + 15,
    		.vsync_end = 600 + 15 + 1,
    		.vtotal = 600 + 15 + 1 + 23,
    		.flags = DRM_MODE_FLAG_NVSYNC | DRM_MODE_FLAG_NHSYNC,
    };
    
    static const struct panel_desc name_desc = {
    	.modes = &name_mode,
    	.num_modes = 1,
    	.bpc = 8,
    	.size = {
    		.width = 154,
    		.height = 86,
    	},
    	.bus_format = MEDIA_BUS_FMT_RGB888_1X24,
    	.connector_type = DRM_MODE_CONNECTOR_DPI,
    };

    4. The LCD data input format and timing are as follows:

     

          

           

    5. Measured by an oscilloscope, the data and sync are latching on falling edge

  • Hi,

    By default, data will latch on rising edge and you already implemented the following in your code: https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1228207/am62a7-rgb-display-flickering-and-pixel-issue/4687209#4687209 

    Also, when you run kmstest, do the output and timing printed on console match your programming? 

    Regards,
    Krunal

  • Hi,

    We found the cause of the problem: the upper and lower 8 bits of RGB were reversed.