test LVDS controller

[EvanKrall]

• see if it enumerates on i2c
• Write device tree overlay
• figure out mode line?
• ???

[EvanKrall]

For posterity, my attempt at a kernel patch to drive this thing:

diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index 204674fccd64..eb1a5950247c 100644
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c
@@ -2570,15 +2570,15 @@ static const struct panel_desc lg_lp079qx1_sp0v = {
 };

 static const struct drm_display_mode lg_lp097qx1_spa1_mode = {
-       .clock = 205210,
-       .hdisplay = 2048,
-       .hsync_start = 2048 + 150,
-       .hsync_end = 2048 + 150 + 5,
-       .htotal = 2048 + 150 + 5 + 5,
-       .vdisplay = 1536,
-       .vsync_start = 1536 + 3,
-       .vsync_end = 1536 + 3 + 1,
-       .vtotal = 1536 + 3 + 1 + 9,
+       .clock = 205210,  // KHz
+       .hdisplay = 2048,  // Active
+       .hsync_start = 2048 + 150,  // Active + HFP
+       .hsync_end = 2048 + 150 + 5, // Active + HFP + Width-Active
+       .htotal = 2048 + 150 + 5 + 5, // Active + HFP + Width-Active + HBP
+       .vdisplay = 1536, // Active
+       .vsync_start = 1536 + 3, // Active + VFP
+       .vsync_end = 1536 + 3 + 1, // Active + VFP + Width-Active
+       .vtotal = 1536 + 3 + 1 + 9, // Active + VFP + Width-Active + VBP
 };

 static const struct panel_desc lg_lp097qx1_spa1 = {
@@ -3889,6 +3889,30 @@ static const struct drm_display_mode arm_rtsm_mode[] = {
        },
 };

+
+static const struct drm_display_mode lg_lp097x02_slq1_mode = {
+       .clock = 100030,  // KHz
+       .hdisplay = 1024,  // Active
+       .hsync_start = 1024 + 260,  // Active + HFP
+       .hsync_end = 1024 + 260 + 320, // Active + HFP + Width-Active
+       .htotal = 1024 + 260 + 320 + 480, // Active + HFP + Width-Active + HBP
+       .vdisplay = 768, // Active
+       .vsync_start = 768 + 16, // Active + VFP
+       .vsync_end = 768 + 16 + 10, // Active + VFP + Width-Active
+       .vtotal = 768 + 16 + 10 + 6, // Active + VFP + Width-Active + VBP
+};
+
+static const struct panel_desc lg_lp097x02_slq1 = {
+       .modes = &lg_lp097qx1_spa1_mode,
+       .num_modes = 1,
+       .size = {
+               .width = 210,
+               .height = 164,
+       },
+};
+
+
+
 static const struct panel_desc arm_rtsm = {
        .modes = arm_rtsm_mode,
        .num_modes = 1,
@@ -4300,6 +4324,9 @@ static const struct of_device_id platform_of_match[] = {
        }, {
                .compatible = "winstar,wf35ltiacd",
                .data = &winstar_wf35ltiacd,
+       }, {
+               .compatible = "lg,lp097x02-slq1",
+               .data = &lg_lp097x02_slq1,
        }, {
                /* Must be the last entry */
                .compatible = "panel-dpi",

I'm roughly following https://github.com/anholt/linux/wiki/Raspberry-Pi-and-other-MIPI-DSI-display-panels , though I'm first starting with panel-simple.c even though I have a bridge chip and it recommends to follow the panel-raspberrypi-touchscreen.c example.

[EvanKrall]

oh, sweet, someone got support for the sn65dsi83 into the linux kernel a few months ago: https://github.com/torvalds/linux/blob/master/drivers/gpu/drm/bridge/ti-sn65dsi83.c

I guess I'll cherry-pick this.

[EvanKrall]

Only RGB888 pixel format is implemented, the
LVDS666 is not supported, but could be added if needed.

bummer

[EvanKrall]

I have this dtoverlay which loads the ti-sn65dsi83 driver:

/dts-v1/;
/plugin/;


/ {
    compatible = "brcm,bcm2835";
    fragment@0 {
        target-path = "/";
        __overlay__ {
            vdd_panel: fixedregulator {
                regulator-boot-on;
                compatible = "regulator-fixed";
                regulator-name = "lvds18";
                regulator-min-microvolt = <1800000>;
                regulator-max-microvolt = <1800000>;
                gpio = <&gpio 26 0>;
                startup-delay-us = <70000>;
                enable-active-high;
                vin-supply = <&vdd_3v3_reg>;
            };

            lcd_bl: backlight {
                compatible = "pwm-backlight";
                pwms = <&pwm 0 200000>;
                brightness-levels = <0 6 8 12 16 24 32 40 48 64 96 128 160 192 224 255>;
                default-brightness-level = <6>;
                power-supply = <&vdd_3v3_reg>;
                enable-gpios = <&gpio 13 0>;
                status = "okay";
            };

            panel_rgb: panel {
              compatible = "lg,lp097x02-slq1";
              // compatible = "koe,tx31d200vm0baa";
              power-supply = <&vdd_panel>;
              // backlight = <&lcd_bl>;
              status = "okay";
              port {
                panel_lvds_in: endpoint {
                  remote-endpoint = <&bridge_lvds_port>;
                };
              };
            };
        };
    };

    fragment@1 {
        target = <&i2c1>;
        __overlay__ {
            #address-cells = <1>;
            #size-cells = <0>;
            status = "okay";

            sn65dsi83_bridge: bridge@2d {
                compatible = "ti,sn65dsi83";
                reg = <0x2d>;
                status = "okay";
                enable-gpios = <&gpio 5 0>;
                power-supply = <&vdd_panel>;

                ports {                
                    #address-cells = <1>;
                    #size-cells = <0>;
                    port@0 {
                        reg = <0>; // TODO: double-check
                        bridge_dsi_port: endpoint {
                            data-lanes = <1 2>;
                            remote-endpoint = <&dsi_out_port>;
                        };
                    };

                    port@2{
                        reg = <2>;
                        bridge_lvds_port: endpoint {
                            remote-endpoint = <&panel_lvds_in>;
                        };
                    };
                };
            };
        };
    };

    fragment@2 {
        target = <&dsi1>;
        __overlay__ {
            compatible = "brcm,bcm2711-dsi1";
            status = "okay";
            port {
                dsi_out_port: endpoint {
                    remote-endpoint = <&bridge_dsi_port>;
                };
            };
        };
    };
};

I've got two problems at the moment:

1. My backlight lights up, but I don't have any entries under /sys/class/backlight
2. The screen is black, and at boot I'm getting the error message [ 5.403630] sn65dsi83 1-002d: failed to lock PLL, ret=-110

[EvanKrall]

I've switched over to the CM4IO using the 22-pin to 15-pin FFC meant for the CSI port, which I think should put clock and data lanes where my board expects them.

Now I'm getting basically this exact error: https://www.raspberrypi.org/forums/viewtopic.php?p=1860828&sid=ad26a9c56f475f1c54610b6eac4ca59f#p1860828

[    5.325798] Bogus possible_crtcs: [ENCODER:31:DSI-31] possible_crtcs=0x0 (full crtc mask=0x1)