Re: [PATCH v1 3/3] ARM: dts: am335x-bone: add support for beaglebone LCD4 cape

["Guido Martínez" <guido@vanguardiasur.com.ar>]

Hi Pekon,

I had some issues with this patch. Booting linux-next on a BeagleBone
Black with this exact LCD left me with an unusable white screen. Please
see below for some details.

On Tue, Jun 24, 2014 at 05:54:26PM +0530, Pekon Gupta wrote:
> This patch adds support for LCD4 cape as advertised on
>   http://elinux.org/CircuitCo:BeagleBone_LCD4
> 
> This cape has:
> * 480x272 TFT-LCD panel
>  - LCD panel datasheet and timing information are sourced from [1]
>  - LCD backlight is connected to 'EHRPWM1A' on cape board, but its used for
>    enabling backlight power-supply. So 'gpio-backlight' driver is used instead
>    of 'pwm-backlight' driver (Kconfig: BACKLIGHT_GPIO=y).
> 
> * 4-wire resistive Touchscreen
> 
> *Known constrains*
> As LCD panel pins (lcd_data, hsync, vsync, pclk) are shared with on-board
> NXP HDMI framer, so either HDMI or LCD-cape can be used at time. Thus while
> using this cape 'hdmi' DT node needs to be disabled in am335x-boneblack.dts
> 
> [1] www.newhavendisplay.com/specs/NHD-4.3-480272MF-ATXI-T-1.pdf
>     www.newhavendisplay.com/app_notes/OTA5180A.pdf
> 
> Signed-off-by: Pekon Gupta <pekon@ti.com>
> ---
>  arch/arm/boot/dts/am335x-bone-display-cape.dts | 104 +++++++++++++++++++++++++
>  arch/arm/boot/dts/am335x-bone.dts              |   1 +
>  arch/arm/boot/dts/am335x-boneblack.dts         |   1 +
>  3 files changed, 106 insertions(+)
>  create mode 100644 arch/arm/boot/dts/am335x-bone-display-cape.dts
> 
> diff --git a/arch/arm/boot/dts/am335x-bone-display-cape.dts b/arch/arm/boot/dts/am335x-bone-display-cape.dts
> new file mode 100644
> index 0000000..f3b7cef
> --- /dev/null
> +++ b/arch/arm/boot/dts/am335x-bone-display-cape.dts
> @@ -0,0 +1,104 @@
> +/*
> + * Copyright (C) 2014 Texas Instruments Incorporated - http://www.ti.com/
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This DTS adds supports for display capes using LCD interface for display
> + * and GPIO or PWM interface for backlight controls.
> + */
> +
> +
> +&am33xx_pinmux {
> +	bbcape_backlight_pins: bbcape_backlight_pins {
> +		pinctrl-single,pins = <
> +			0x48  (PIN_OUTPUT | MUX_MODE7)		/* gpmc_a[2].GPIO1[18] (backlight control) */
> +		>;
> +	};
> +
> +	bbcape_lcd_pins: bbcape_lcd_pins {
> +		pinctrl-single,pins = <
> +			0xa0 (PIN_OUTPUT | MUX_MODE0)		/* lcd_data0.lcd_data0 */
> +			0xa4 (PIN_OUTPUT | MUX_MODE0)		/* lcd_data1.lcd_data1 */
> +			0xa8 (PIN_OUTPUT | MUX_MODE0)		/* lcd_data2.lcd_data2 */
> +			0xac (PIN_OUTPUT | MUX_MODE0)		/* lcd_data3.lcd_data3 */
> +			0xb0 (PIN_OUTPUT | MUX_MODE0)		/* lcd_data4.lcd_data4 */
> +			0xb4 (PIN_OUTPUT | MUX_MODE0)		/* lcd_data5.lcd_data5 */
> +			0xb8 (PIN_OUTPUT | MUX_MODE0)		/* lcd_data6.lcd_data6 */
> +			0xbc (PIN_OUTPUT | MUX_MODE0)		/* lcd_data7.lcd_data7 */
> +			0xc0 (PIN_OUTPUT | MUX_MODE0)		/* lcd_data8.lcd_data8 */
> +			0xc4 (PIN_OUTPUT | MUX_MODE0)		/* lcd_data9.lcd_data9 */
> +			0xc8 (PIN_OUTPUT | MUX_MODE0)		/* lcd_data10.lcd_data10 */
> +			0xcc (PIN_OUTPUT | MUX_MODE0)		/* lcd_data11.lcd_data11 */
> +			0xd0 (PIN_OUTPUT | MUX_MODE0)		/* lcd_data12.lcd_data12 */
> +			0xd4 (PIN_OUTPUT | MUX_MODE0)		/* lcd_data13.lcd_data13 */
> +			0xd8 (PIN_OUTPUT | MUX_MODE0)		/* lcd_data14.lcd_data14 */
> +			0xdc (PIN_OUTPUT | MUX_MODE0)		/* lcd_data15.lcd_data15 */
> +			0xe0 (PIN_OUTPUT | MUX_MODE0)		/* lcd_vsync.lcd_vsync */
> +			0xe4 (PIN_OUTPUT | MUX_MODE0)		/* lcd_hsync.lcd_hsync */
> +			0xe8 (PIN_OUTPUT | MUX_MODE0)		/* lcd_pclk.lcd_pclk */
> +			0xec (PIN_OUTPUT | MUX_MODE0)		/* lcd_ac_bias_en.lcd_ac_bias_en (lcd_en) */
> +			0x1a4 (PIN_OUTPUT_PULLUP | MUX_MODE7)	/* mcasp0_fsr.gpio3[19] (lcd_disen) */
> +		>;
> +	};
> +
> +	bbcape_touchscreen_pins: bbcape_touchscreen_pins {
> +		pinctrl-single,pins = <
> +			0x184 (PIN_INPUT_PULLDOWN | MUX_MODE7)		/* uart1_txd.gpio0[15] (enter) */
> +			0x40  (PIN_INPUT_PULLDOWN | MUX_MODE7)		/* gpmc_a0.gpio1[16] (left) */
> +			0x44  (PIN_INPUT_PULLDOWN | MUX_MODE7)		/* gpmc_a1.gpio1[17] (right) */
> +			0x4c  (PIN_INPUT_PULLDOWN | MUX_MODE7)		/* gpmc_a3.gpio1[19] (up) */
> +			0x198 (PIN_INPUT_PULLDOWN | MUX_MODE7)		/* mcasp0_axr0.gpio3[16] (down) */
> +		>;
> +	};
> +};
> +
> +
> +/ {
> +	backlight {
> +		status = "disabled";
> +		compatible = "gpio-backlight";
> +		pinctrl-names = "default";
> +		pinctrl-0 = <&bbcape_backlight_pins>;
> +		gpios = <&gpio1 18 GPIO_ACTIVE_HIGH>;
> +		default-on;
> +	};
> +
> +	panel {
> +		status = "disabled";
> +		compatible = "ti,tilcdc,panel";
> +		pinctrl-names = "default";
> +		pinctrl-0 = <&bbcape_lcd_pins>;
> +		panel-info {
> +			ac-bias           = <255>;
> +			ac-bias-intrpt    = <0>;
> +			dma-burst-sz      = <16>;
> +			bpp               = <16>;
> +			fdd               = <0x80>;
> +			sync-edge         = <0>;
> +			sync-ctrl         = <0>;
I had to set this to <1>. Does that make sense? 

> +			raster-order      = <0>;
> +			fifo-th           = <0>;
> +		};
> +		display-timings {
> +			native-mode = <&timing0>;
> +			/* www.newhavendisplay.com/app_notes/OTA5180A.pdf */
> +			timing0: 480x272 {
> +				clock-frequency = <30000000>;
> +				hactive = <480>;
> +				vactive = <272>;
> +				hfront-porch = <8>;
> +				hback-porch = <47>;
> +				hsync-len = <41>;
> +				vback-porch = <2>;
> +				vfront-porch = <3>;
> +				vsync-len = <10>;
> +				hsync-active = <0>;
> +				vsync-active = <0>;
> +				de-active = <1>;
> +				pixelclk-active = <0>;
Are you sure these timings are ok? When enabling the sync control I get
an usable display, but it looks a bit funny. For example an all black
display looks very clear and has a dotted pattern.

I tried to take a picture of it but it doesn't show.

Also I'm just guessing about the timings, maybe it's something else?

> +			};
> +		};
> +	};
> +};
> diff --git a/arch/arm/boot/dts/am335x-bone.dts b/arch/arm/boot/dts/am335x-bone.dts
> index f16bfcf..41439dc 100644
> --- a/arch/arm/boot/dts/am335x-bone.dts
> +++ b/arch/arm/boot/dts/am335x-bone.dts
> @@ -10,6 +10,7 @@
>  #include "am33xx.dtsi"
>  #include "am335x-bone-common.dtsi"
>  #include "am335x-bone-memory-cape.dts"
> +#include "am335x-bone-display-cape.dts"
>  
>  &ldo3_reg {
>  	regulator-min-microvolt = <1800000>;
> diff --git a/arch/arm/boot/dts/am335x-boneblack.dts b/arch/arm/boot/dts/am335x-boneblack.dts
> index e6d7e54..03232c7 100644
> --- a/arch/arm/boot/dts/am335x-boneblack.dts
> +++ b/arch/arm/boot/dts/am335x-boneblack.dts
> @@ -10,6 +10,7 @@
>  #include "am33xx.dtsi"
>  #include "am335x-bone-common.dtsi"
>  #include "am335x-bone-memory-cape.dts"
> +#include "am335x-bone-display-cape.dts"
>  
>  &ldo3_reg {
>  	regulator-min-microvolt = <1800000>;
> -- 
> 1.8.5.1.163.gd7aced9
> 
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-- 
Guido Martínez, VanguardiaSur
www.vanguardiasur.com.ar