lcd的驱动也不需要自己写，而是在设备树中配置好即可。
设备树
panel {
compatible = "ti,tilcdc,panel";
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&lcd_pins_s0>;
panel-info {
ac-bias = <255>;
ac-bias-intrpt = <0>;
dma-burst-sz = <16>;
bpp = <16>;
fdd = <255>;
sync-edge = <0>;
sync-ctrl = <1>;
raster-order = <0>;
fifo-th = <6>;
};
display-timings {
800x480p62 {
clock-frequency = <30000000>;
hactive = <640>;
vactive = <480>;
hfront-porch = <16>;
hback-porch = <144>;
hsync-len = <10>;
vback-porch = <13>;
vfront-porch = <32>;
vsync-len = <2>;
hsync-active = <1>;
vsync-active = <1>;
};
};
};
lcd_pins_s0: lcd_pins_s0 {
pinctrl-single,pins = <
0x20 0x01 /* gpmc_ad8.lcd_data16, OUTPUT | MODE1 */
0x24 0x01 /* gpmc_ad9.lcd_data17, OUTPUT | MODE1 */
0x28 0x01 /* gpmc_ad10.lcd_data18, OUTPUT | MODE1 */
0x2c 0x01 /* gpmc_ad11.lcd_data19, OUTPUT | MODE1 */
0x30 0x01 /* gpmc_ad12.lcd_data20, OUTPUT | MODE1 */
0x34 0x01 /* gpmc_ad13.lcd_data21, OUTPUT | MODE1 */
0x38 0x01 /* gpmc_ad14.lcd_data22, OUTPUT | MODE1 */
0x3c 0x01 /* gpmc_ad15.lcd_data23, OUTPUT | MODE1 */
0xa0 0x00 /* lcd_data0.lcd_data0, OUTPUT | MODE0 */
0xa4 0x00 /* lcd_data1.lcd_data1, OUTPUT | MODE0 */
0xa8 0x00 /* lcd_data2.lcd_data2, OUTPUT | MODE0 */
0xac 0x00 /* lcd_data3.lcd_data3, OUTPUT | MODE0 */
0xb0 0x00 /* lcd_data4.lcd_data4, OUTPUT | MODE0 */
0xb4 0x00 /* lcd_data5.lcd_data5, OUTPUT | MODE0 */
0xb8 0x00 /* lcd_data6.lcd_data6, OUTPUT | MODE0 */
0xbc 0x00 /* lcd_data7.lcd_data7, OUTPUT | MODE0 */
0xc0 0x00 /* lcd_data8.lcd_data8, OUTPUT | MODE0 */
0xc4 0x00 /* lcd_data9.lcd_data9, OUTPUT | MODE0 */
0xc8 0x00 /* lcd_data10.lcd_data10, OUTPUT | MODE0 */
0xcc 0x00 /* lcd_data11.lcd_data11, OUTPUT | MODE0 */
0xd0 0x00 /* lcd_data12.lcd_data12, OUTPUT | MODE0 */
0xd4 0x00 /* lcd_data13.lcd_data13, OUTPUT | MODE0 */
0xd8 0x00 /* lcd_data14.lcd_data14, OUTPUT | MODE0 */
0xdc 0x00 /* lcd_data15.lcd_data15, OUTPUT | MODE0 */
0xe0 0x00 /* lcd_vsync.lcd_vsync, OUTPUT | MODE0 */
0xe4 0x00 /* lcd_hsync.lcd_hsync, OUTPUT | MODE0 */
0xe8 0x00 /* lcd_pclk.lcd_pclk, OUTPUT | MODE0 */
0xec 0x00 /* lcd_ac_bias_en.lcd_ac_bias_en, OUTPUT | MODE0 */
>;
};配置参数
配置lcd对应的管脚，方法前面已说过。
配置lcd的参数，这个需要根据自己的lcd设备spec来设置。
display-timings
在Documentation/devicetree/bindings/video/display-timing.txt有详细描述。
display-timings node
--------------------
required properties:
- none
optional properties:
- native-mode: The native mode for the display, in case multiple modes are
provided. When omitted, assume the first node is the native.
timing subnode
--------------
required properties:
- hactive, vactive: display resolution
- hfront-porch, hback-porch, hsync-len: horizontal display timing parameters
in pixels
vfront-porch, vback-porch, vsync-len: vertical display timing parameters in
lines
- clock-frequency: display clock in Hz
optional properties:
- hsync-active: hsync pulse is active low/high/ignored
- vsync-active: vsync pulse is active low/high/ignored
- de-active: data-enable pulse is active low/high/ignored
- pixelclk-active: with
- active high = drive pixel data on rising edge/
sample data on falling edge
- active low = drive pixel data on falling edge/
sample data on rising edge
- ignored = ignored
- interlaced (bool): boolean to enable interlaced mode
- doublescan (bool): boolean to enable doublescan mode
- doubleclk (bool): boolean to enable doubleclock mode
All the optional properties that are not bool follow the following logic:
<1>: high active
<0>: low active
omitted: not used on hardware
There are different ways of describing the capabilities of a display. The
devicetree representation corresponds to the one commonly found in datasheets
for displays. If a display supports multiple signal timings, the native-mode
can be specified.
The parameters are defined as:
+----------+-------------------------------------+----------+-------+
| | ↑ | | |
| | |vback_porch | | |
| | ↓ | | |
+----------#######################################----------+-------+
| # ↑ # | |
| # | # | |
| hback # | # hfront | hsync |
| porch # | hactive # porch | len |
|<-------->#<-------+--------------------------->#<-------->|<----->|
| # | # | |
| # |vactive # | |
| # | # | |
| # ↓ # | |
+----------#######################################----------+-------+
| | ↑ | | |
| | |vfront_porch | | |
| | ↓ | | |
+----------+-------------------------------------+----------+-------+
| | ↑ | | |
| | |vsync_len | | |
| | ↓ | | |
+----------+-------------------------------------+----------+-------+
Example:
display-timings {
native-mode = <&timing0>;
timing0: 1080p24 {
/* 1920x1080p24 */
clock-frequency = <52000000>;
hactive = <1920>;
vactive = <1080>;
hfront-porch = <25>;
hback-porch = <25>;
hsync-len = <25>;
vback-porch = <2>;
vfront-porch = <2>;
vsync-len = <2>;
hsync-active = <1>;
};
};
Every required property also supports the use of ranges, so the commonly used
datasheet description with minimum, typical and maximum values can be used.
Example:
timing1: timing {
/* 1920x1080p24 */
clock-frequency = <148500000>;
hactive = <1920>;
vactive = <1080>;
hsync-len = <0 44 60>;
hfront-porch = <80 88 95>;
hback-porch = <100 148 160>;
vfront-porch = <0 4 6>;
vback-porch = <0 36 50>;
vsync-len = <0 5 6>;
};panel-info
在Documentation/devicetree/bindings/drm/tilcdc/panel.txt有详细描述。
Device-Tree bindings for tilcdc DRM generic panel output driver
Required properties:
- compatible: value should be "ti,tilcdc,panel".
- panel-info: configuration info to configure LCDC correctly for the panel
- ac-bias: AC Bias Pin Frequency
- ac-bias-intrpt: AC Bias Pin Transitions per Interrupt
- dma-burst-sz: DMA burst size
- bpp: Bits per pixel
- fdd: FIFO DMA Request Delay
- sync-edge: Horizontal and Vertical Sync Edge: 0=rising 1=falling
- sync-ctrl: Horizontal and Vertical Sync: Control: 0=ignore
- raster-order: Raster Data Order Select: 1=Most-to-least 0=Least-to-most
- fifo-th: DMA FIFO threshold
- display-timings: typical videomode of lcd panel. Multiple video modes
can be listed if the panel supports multiple timings, but the 'native-mode'
should be the preferred/default resolution. Refer to
Documentation/devicetree/bindings/video/display-timing.txt for display
timing binding details.
Recommended properties:
- pinctrl-names, pinctrl-0: the pincontrol settings to configure
muxing properly for pins that connect to TFP410 device
Example:
/* Settings for CDTech_S035Q01 / LCD3 cape: */
lcd3 {
compatible = "ti,tilcdc,panel";
pinctrl-names = "default";
pinctrl-0 = <&bone_lcd3_cape_lcd_pins>;
panel-info {
ac-bias = <255>;
ac-bias-intrpt = <0>;
dma-burst-sz = <16>;
bpp = <16>;
fdd = <0x80>;
sync-edge = <0>;
sync-ctrl = <1>;
raster-order = <0>;
fifo-th = <0>;
};
display-timings {
native-mode = <&timing0>;
timing0: 320x240 {
hactive = <320>;
vactive = <240>;
hback-porch = <21>;
hfront-porch = <58>;
hsync-len = <47>;
vback-porch = <11>;
vfront-porch = <23>;
vsync-len = <2>;
clock-frequency = <8000000>;
hsync-active = <0>;
vsync-active = <0>;
};
};
};另外，需要确保tilcdc驱动使能。