AM3358: AM33x TICLICD linux clarification DPI to LVDS converter

alexandre leblanc

Part Number: AM3358
Other Parts Discussed in Thread: SN65LVDS84A

Hello !

So, I'm trying to integrate a LVDS panel via the SN65LVDS84A .
According to TI , currently the way to integrate a new panel is to make use of the TILCDC linux driver .
This driver, as far as I understand, has 2 layers The DRM part and the panel part.

Looking at the linux documentation , in the DTS I should have a node "lcdc" compatible with "ti,am33xx-tilcdc" .
This is the default set in the original beaglebone black DTS.

A second node should contain my panel definition and be compatible with "ti,tilcdc,panel" .
The plan is to drive the SN65LVDS84A from the CPU directly over DPI config and let the SN65LVDS84A convert to LVDS.
(the orignal definition to HDMI have been removed from the DTS)

At the moment I can get the DRM driver to load and create a FB0. But obviously... the panel is not working and backlight is not turning on.
The backlight controller mux did not changed from our previous known working configuration.

So one of my first questions is, am I right to use TI's TILCDC driver to drive the LVDS panel via the SN65LVDS84A ?
OR should I be using the DPI driver (the simple-panel dts config)?

What could I be missing in the DTS to get the panel to work?

Looking around .. the information online (and on TI forum) seems to go multiple ways and not being up to date.

also , we use linux-sti-staging 5.10 from the OE meta-ti layer

Thanks a lot !

&lcdc {
status = "okay";
/delete-node/ port;
};

panel {
compatible = "ti,tilcdc,panel";
   status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&lcdc_pins>;
backlight = <&backlight>;
// LCD_EN
enable-gpios = <&gpio0 26 GPIO_ACTIVE_HIGH>;

panel-info {
ac-bias           = <255>; /** AC Bias Pin Frequency **/
ac-bias-intrpt    = <0>; /** AC Bias Pin Transitions per Interrupt **/
dma-burst-sz      = <16>; /** DMA Burst Size **/
bpp               = <16>; /** Bits per pixel **/
fdd               = <0x80>; /** FIFO DMA Request Delay **/
sync-edge         = <0>; /** Horizontal and Vertical Sync Edge: 0=rising 1=falling **/
sync-ctrl         = <1>; /** Horizontal and Vertical Sync: Control: 0=ignore **/
raster-order      = <0>; /** Raster Data Order Select: 1=Most-to-least 0=Least-to-most **/
fifo-th           = <0>; /** DMA FIFO threshold **/
};

display-timings {
native-mode=<&timing0>;
timing0: 1024x728 {
hactive         = <1024>;
vactive         = <768>;
clock-frequency = <60000000>;

vsync-len       = <2>;
hsync-len       = <10>;
vfront-porch    = <3>;
vback-porch     = <4>;
hfront-porch    = <14>;
hback-porch     = <40>;

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

panel {
compatible = "ti,tilcdc,panel";
   status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&lcdc_pins>;
backlight = <&backlight>;
// LCD_EN
enable-gpios = <&gpio0 26 GPIO_ACTIVE_HIGH>;

panel-info {
ac-bias           = <255>; /** AC Bias Pin Frequency **/
ac-bias-intrpt    = <0>; /**  AC Bias Pin Transitions per Interrupt **/
dma-burst-sz      = <16>; /** DMA Burst Size **/
bpp               = <16>; /** Bits per pixel **/
fdd               = <0x80>; /** FIFO DMA Request Delay **/
sync-edge         = <0>; /** Horizontal and Vertical Sync Edge: 0=rising 1=falling **/
sync-ctrl         = <1>; /** Horizontal and Vertical Sync: Control: 0=ignore **/
raster-order      = <0>; /** Raster Data Order Select: 1=Most-to-least 0=Least-to-most **/
fifo-th           = <0>; /** DMA FIFO threshold **/
};

display-timings {
native-mode=<&timing0>;
timing0: 1024x728 {
hactive         = <1024>;
vactive         = <768>;
clock-frequency = <60000000>;

vsync-len       = <2>;
hsync-len       = <10>;
vfront-porch    = <3>;
vback-porch     = <4>;
hfront-porch    = <14>;
hback-porch     = <40>;
de-active       = <1>;
};
};
};


    lcdc_pins: pinmux_lcdc_pins {
pinctrl-single,pins = <
            AM33XX_PADCONF(AM335X_PIN_LCD_DATA0, PIN_OUTPUT, MUX_MODE0) /* LCD_DATA0 */
            AM33XX_PADCONF(AM335X_PIN_LCD_DATA1, PIN_OUTPUT, MUX_MODE0) /* LCD_DATA1 */
            AM33XX_PADCONF(AM335X_PIN_LCD_DATA2, PIN_OUTPUT, MUX_MODE0) /* LCD_DATA2 */
            AM33XX_PADCONF(AM335X_PIN_LCD_DATA3, PIN_OUTPUT, MUX_MODE0) /* LCD_DATA3 */
            AM33XX_PADCONF(AM335X_PIN_LCD_DATA4, PIN_OUTPUT, MUX_MODE0) /* LCD_DATA4 */
            AM33XX_PADCONF(AM335X_PIN_LCD_DATA5, PIN_OUTPUT, MUX_MODE0) /* LCD_DATA5 */
            AM33XX_PADCONF(AM335X_PIN_LCD_DATA6, PIN_OUTPUT, MUX_MODE0) /* LCD_DATA6 */
            AM33XX_PADCONF(AM335X_PIN_LCD_DATA7, PIN_OUTPUT, MUX_MODE0) /* LCD_DATA7 */
            AM33XX_PADCONF(AM335X_PIN_LCD_DATA8, PIN_OUTPUT, MUX_MODE0) /* LCD_DATA8 */
            AM33XX_PADCONF(AM335X_PIN_LCD_DATA9, PIN_OUTPUT, MUX_MODE0) /* LCD_DATA9 */
            AM33XX_PADCONF(AM335X_PIN_LCD_DATA10, PIN_OUTPUT, MUX_MODE0) /* LCD_DATA10 */
            AM33XX_PADCONF(AM335X_PIN_LCD_DATA11, PIN_OUTPUT, MUX_MODE0) /* LCD_DATA11 */
            AM33XX_PADCONF(AM335X_PIN_LCD_DATA12, PIN_OUTPUT, MUX_MODE0) /* LCD_DATA12 */
            AM33XX_PADCONF(AM335X_PIN_LCD_DATA13, PIN_OUTPUT, MUX_MODE0) /* LCD_DATA13 */
            AM33XX_PADCONF(AM335X_PIN_LCD_DATA14, PIN_OUTPUT, MUX_MODE0) /* LCD_DATA14 */
            AM33XX_PADCONF(AM335X_PIN_LCD_DATA15, PIN_OUTPUT, MUX_MODE0) /* LCD_DATA15 */
            AM33XX_PADCONF(AM335X_PIN_LCD_AC_BIAS_EN, PIN_OUTPUT, MUX_MODE0) /* LCD_DE */
            AM33XX_PADCONF(AM335X_PIN_LCD_PCLK, PIN_OUTPUT, MUX_MODE0) /* LCD_CLK */

            /* bbek4l mods */
            AM33XX_PADCONF(AM335X_PIN_LCD_VSYNC, PIN_OUTPUT, MUX_MODE7) /* LCD_VSYNC */
            AM33XX_PADCONF(AM335X_PIN_LCD_HSYNC, PIN_OUTPUT, MUX_MODE7) /* LCD_HSYNC */
            AM33XX_PADCONF(AM335X_PIN_GPMC_AD10, PIN_OUTPUT, MUX_MODE7) /* LCD_EN for SN65LVDS84AQDGG */
            AM33XX_PADCONF(AM335X_PIN_GPMC_AD9, PIN_OUTPUT, MUX_MODE7)  /* LCD_POWER_EN  both the LCD backlight and SN65LVDS84AQDGG */
>;
};

over 1 year ago

0 Krunal Bhargav34 over 1 year ago

TI__Mastermind 44915 points

Hi,

As you mentioned, there are multiple ways of configuring the TILCDC. Refer to our 5.10 example: https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/tree/arch/arm/boot/dts/am335x-evmsk.dts?h=ti-linux-5.10.y

1. Panel entry gets defined and the timing information is available in panel-simple.c: https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/tree/arch/arm/boot/dts/am335x-evmsk.dts?h=ti-linux-5.10.y#n185 and https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/tree/drivers/gpu/drm/panel/panel-simple.c?h=ti-linux-5.10.y#n2968

2. Besides the panel, you need to configure the tilcdc and that's done here: https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/tree/arch/arm/boot/dts/am335x-evmsk.dts?h=ti-linux-5.10.y#n722

If possible try to structure your DT based on the above information and let me know if it helps you get further in debugging,

Regards,
Krunal

0 alexandre leblanc over 1 year ago in reply to Krunal Bhargav34

Prodigy 20 points

Hum, looking at https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/tree/drivers/gpu/drm/panel/panel-simple.c?h=ti-linux-5.10.y#n2968 , this specific panel uses drm_display_mode... Should I use that or display_timing ? The previous panel we used was a "okaya,rs800480t-7x0gp"

0 alexandre leblanc over 1 year ago in reply to Krunal Bhargav34

Prodigy 20 points

this is now the new config

&lcdc {
	status = "okay";
	blue-and-red-wiring = "straight";
	/delete-node/ port;
	port {
			lcdc_0: endpoint@0 {
					remote-endpoint = <&panel_0>;
			};
	};
};

panel {
        // new display 
		compatible = "zettler,atm1210l9-oct2";
	    status = "okay";
		pinctrl-names = "default";
		pinctrl-0 = <&lcdc_pins>;
		backlight = <&backlight>;
		// LCD_EN 
		enable-gpios = <&gpio0 26 GPIO_ACTIVE_HIGH>;

		port {
			panel_0: endpoint@0 {
				remote-endpoint = <&lcdc_0>;
			};
		};
	};

and the new display definition

---
 drivers/gpu/drm/panel/panel-simple.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index 2be358fb46f7..f99468ad67f1 100644
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c
@@ -3873,6 +3873,30 @@ static const struct panel_desc winstar_wf35ltiacd = {
 	.bus_format = MEDIA_BUS_FMT_RGB888_1X24,
 };
 
+static const struct display_timing zettler_atm1210l9_oct2_timing = {
+	.pixelclock = { 60000000, 60000000, 60000000 },
+	.hactive = { 1024, 1024, 1024 },
+	.hfront_porch = { 14, 14, 14 },
+	.hback_porch = { 40, 40, 40 },
+	.hsync_len = { 10, 10, 10 },
+	.vactive = { 768, 768, 768 },
+	.vfront_porch = { 3, 3, 3 },
+	.vback_porch = { 4, 4, 4 },
+	.vsync_len = { 2, 2, 2 },
+	.flags = DISPLAY_FLAGS_DE_HIGH,
+};
+
+static const struct panel_desc zettler_atm1210l9_oct2 = {
+	.timings = &zettler_atm1210l9_oct2_timing,
+	.num_timings = 1 ,
+	.bpc = 16,
+	.size = {
+		.width = 245.76,
+		.height = 184.32,
+	},
+	.bus_format = MEDIA_BUS_FMT_RGB666_1X18,
+};
+
 static const struct drm_display_mode arm_rtsm_mode[] = {
 	{
 		.clock = 65000,
@@ -4299,6 +4323,9 @@ static const struct of_device_id platform_of_match[] = {
 	}, {
 		.compatible = "winstar,wf35ltiacd",
 		.data = &winstar_wf35ltiacd,
+	},{
+		.compatible = "zettler,atm1210l9-oct2",
+		.data = &zettler_atm1210l9_oct2,
 	}, {
 		/* Must be the last entry */
 		.compatible = "panel-dpi",
-- 
2.30.2

0 Krunal Bhargav34 over 1 year ago in reply to alexandre leblanc

TI__Mastermind 44915 points

Hi,

What happens when you run kmsprint in Linux?

Regards,
Krunal

0 alexandre leblanc over 1 year ago in reply to Krunal Bhargav34

Prodigy 20 points

Krunal

I was to make it make it work using the following config . But ! I'm not sure why it's working. The "ldc" node is a am33xx-tilcdc node that refer to https://elixir.bootlin.com/linux/v5.10.214/source/Documentation/devicetree/bindings/display/tilcdc/tilcdc.txt . For that node , there is no mention of having a "pinctrl" as a requirement . Could it be some sort DTS magic related somewhere ?

	panel {
		compatible = "zettler,atm1210l9_oct2";
	    status = "okay";
		
		pinctrl-names = "default";
		pinctrl-0 = <&panel_pins>;

		enable-gpios = <&gpio0 26 GPIO_ACTIVE_HIGH>;

		backlight = <&backlight>;

		port {
			panel_0: endpoint@0 {
				remote-endpoint = <&lcdc_0>;
			};
		};
	};
	
	
	&lcdc {
	pinctrl-names = "default";
	pinctrl-0 = <&lcdc_pins>;
	status = "okay";
	blue-and-red-wiring = "straight";

	/delete-node/ port;
	port {
			lcdc_0: endpoint@0 {
					remote-endpoint = <&panel_0>;
			};
	    };
    };

0 Krunal Bhargav34 over 1 year ago in reply to alexandre leblanc

TI__Mastermind 44915 points

Hi,

I am not sure if I follow but you do have pinctrl defined for the lcdc.

Regards,
Krunal

0 alexandre leblanc over 1 year ago in reply to Krunal Bhargav34

Prodigy 20 points

I guess what I'm saying is, the linux documentation make use of a complete different method that does not seems to work. see Linux TILCDC panel

And the TI documentation does not mention anything other than HDMI see AM335x LCDC DRM Display Driver

The TLDR is , and for anyone with the same issue: use the Beaglebone lcd node to link to a simple panel , see my previous post

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AM3358: AM33x TICLICD linux clarification DPI to LVDS converter