src/arm/BB-SPIDEV1-00A0.dts modify to add tinydrm st7735r for Adafruit 1.8" TFT LCD connected to BeagleBone Black running 4.16.0-rc2-bone3 kernel. More info: https://groups.google.com/d/msg/beagleboard/GuMQIP_XCW0/b3lxbx_8AwAJ

BB-SPIDEV1-00A0.dts

/*
 * Copyright (C) 2013 CircuitCo
 *
 * Virtual cape for SPI1 on connector pins P9.29 P9.31 P9.30 P9.28
 *
 * 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.
 */

#include <dt-bindings/pinctrl/am33xx.h>

/dts-v1/;
/plugin/;

/ {
	compatible = "ti,beaglebone", "ti,beaglebone-black", "ti,beaglebone-green";

	/* identification */
	part-number = "BB-SPIDEV1";
	version = "00A0";

	/* state the resources this cape uses */
	exclusive-use =
		/* the pin header uses */
		"P9.31",	/* spi1_sclk */
		"P9.29",	/* spi1_d0 */
		"P9.30",	/* spi1_d1 */
		"P9.28",	/* spi1_cs0 */
		// "P9.42",	/* spi1_cs1 */
		/* the hardware ip uses */
		"spi1";

	fragment@0 {
		target = <&am33xx_pinmux>;
		__overlay__ {
			/* default state has all gpios released and mode set to uart1 */
			bb_spi1_pins: pinmux_bb_spi1_pins {
				pinctrl-single,pins = <
					0x190 0x33	/* mcasp0_aclkx.spi1_sclk, INPUT_PULLUP | MODE3 */
					0x194 0x33	/* mcasp0_fsx.spi1_d0, INPUT_PULLUP | MODE3 */
					0x198 0x13	/* mcasp0_axr0.spi1_d1, OUTPUT_PULLUP | MODE3 */
					0x19c 0x13	/* mcasp0_ahclkr.spi1_cs0, OUTPUT_PULLUP | MODE3 */
					// 0x164 0x12	/* eCAP0_in_PWM0_out.spi1_cs1 OUTPUT_PULLUP | MODE2 */
				>;
			};
		};
	};

	fragment@1 {
		target = <&spi1>;
		__overlay__ {
			#address-cells = <1>;
			#size-cells = <0>;

			status = "okay";
			pinctrl-names = "default";
			pinctrl-0 = <&bb_spi1_pins>;
			ti,pio-mode; /* disable dma when used as an overlay, dma gets stuck at 160 bits... */

			/*channel@0 {
				#address-cells = <1>;
				#size-cells = <0>;

				compatible = "spidev";

				reg = <0>;
				spi-max-frequency = <16000000>;
				spi-cpha;
			};

			channel@1 {
				#address-cells = <1>;
				#size-cells = <0>;

				compatible = "spidev";

				reg = <1>;
				spi-max-frequency = <16000000>;
			};*/

                       display@0{
                               status = "okay";
                               compatible = "jianda,jd-t18003-t01", "sitronix,st7735r";
                               reg = <0>;
                               spi-max-frequency = <16000000>;
                               /* https://elinux.org/Beagleboard:Cape_Expansion_Headers */
                               dc-gpios = <&gpio1 16 0>;    /* dc:48    P9.15 GPIO1_16 */
                               reset-gpios = <&gpio1 28 0>; /* reset:60 P9.12 GPIO1_28 */
                               /* rotation = <270>; */
                       };


		};
	};
};

[   14.444344] 8021q: adding VLAN 0 to HW filter on device eth0
[   20.485135] tinydrm/st7735r: st7735r_probe(): begin
[   20.696053] tinydrm/st7735r: st7735r_probe(): call devm_gpiod_get(reset)
[   20.996317] tinydrm/st7735r: st7735r_probe(): call devm_gpiod_get(dc)
[   21.280270] tinydrm/st7735r: st7735r_probe(): call tinydrm_of_find_backlight()
[   21.287600] tinydrm/st7735r: st7735r_probe(): call mipi_dbi_spi_init()
[   21.294211] tinydrm/st7735r: st7735r_probe(): call mipi_dbi_init()
[   22.200619] [drm] Initialized st7735r 1.0.0 20171128 for spi1.0 on minor 0
[   22.213325] tinydrm/st7735r: jd_t18003_t01_pipe_enable(): begin
[   22.213332] tinydrm/st7735r: jd_t18003_t01_pipe_enable(): call mipi_dbi_hw_reset()
[   22.372926] tinydrm/st7735r: jd_t18003_t01_pipe_enable(): call mipi_dbi_command(mipi, MIPI_DCS_SOFT_RESET)
[   22.532130] tinydrm/st7735r: jd_t18003_t01_pipe_enable(): call mipi_dbi_command(mipi, MIPI_DCS_EXIT_SLEEP_MODE)
[   22.552490] random: crng init done
[   23.184205] tinydrm/st7735r: jd_t18003_t01_pipe_enable(): call mipi_dbi_pipe_enable(pipe, crtc_state)
[   23.209772] Console: switching to colour frame buffer device 20x16
[   24.147316] st7735r spi1.0: fb0:  frame buffer device

debian@beaglebone:~/libdrm/tests/modetest$ ./modetest -M st7735r |head
Encoders:
id	crtc	type	possible crtcs	possible clones	
31	30	none	0x00000001	0x00000000

Connectors:
id	encoder	status		name		size (mm)	modes	encoders
28	31	connected	Virtual-1      	35x28		1	31
  modes:
	name refresh (Hz) hdisp hss hse htot vdisp vss vse vtot)
  160x128 0 160 160 160 160 128 128 128 128 1 flags: ; type: preferred, driver

debian@beaglebone:~/libdrm/tests/modetest$ sudo ./modetest -M st7735r -s 28:160x128 
setting mode 160x128-0Hz@XR24 on connectors 28, crtc 30

debian@beaglebone:~/libdrm/tests/modetest$ find |grep modetest^C
debian@beaglebone:~/libdrm/tests/modetest$ sudo ./modetest -M st7735r -s 28:160x128 -v
setting mode 160x128-0Hz@XR24 on connectors 28, crtc 30
freq: 37.50Hz
freq: 37.43Hz

For anyone interested, here is a discussion thread about using this Adafruit 1.8" TFT LCD with tinydrm on BeagleBone.

PWM backlight example in BB-BONE-4D4C-01-00A1.dts:

        fragment@1 {
                target = <&am33xx_pinmux>;
                __overlay__ {

                        bb_lcd_pwm_backlight_pins: pinmux_bb_lcd_pwm_backlight_pins {
                                pinctrl-single,pins = <
                                        BONE_P9_14 0x06 /* gpmc_a2.ehrpwm1a, OMAP_MUX_MODE6 | AM33XX_PIN_OUTPUT */
                                >;
                        };

        fragment@6 {
                target-path="/";
                __overlay__ {

                        /* avoid stupid warning */
                        #address-cells = <1>;
                        #size-cells = <1>;

                        backlight {
                                status = "okay";
                                compatible = "pwm-backlight";
                                pwms = <&ehrpwm1 0 500000 0>;
                                brightness-levels = <
                                        0  1  2  3  4  5  6  7  8  9
                                        10 11 12 13 14 15 16 17 18 19
                                        20 21 22 23 24 25 26 27 28 29
                                        30 31 32 33 34 35 36 37 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
                                >;
                                default-brightness-level = <100>;
                        };