LCD使用¶
LVDS屏¶
DTS配置¶
引脚配置¶
AIO-3399J的SDK有LVDS DSI的DTS文件：kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-aio-lvds.dts，从该文件中我们可以看到以下语句：
/ {
model = "AIO Board lvds (Android)";
compatible = "rockchip,android", "rockchip,rk3399-firefly-lvds", "rockchip,rk3399";
test-power {
status = "okay";
};
...
&dsi {
status = "okay";
dsi_panel: panel {
compatible ="simple-panel-dsi";
reg = <0>;
//ddc-i2c-bu
//power-supply = <&vcc_lcd>;
//pinctrl-0 = <&lcd_panel_reset &lcd_panel_enable>;
backlight = <&backlight>;
/*
enable-gpios = <&gpio1 1 GPIO_ACTIVE_LOW>;
reset-gpios = <&gpio4 29 GPIO_ACTIVE_LOW>;
*/
dsi,flags = <(MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_BURST | MIPI_DSI_MODE_LPM | MIPI_DSI_MODE_EOT_PACKET)>;
dsi,format = <MIPI_DSI_FMT_RGB888>;
//bus-format = <MEDIA_BUS_FMT_RGB666_1X18>;
dsi,lanes = <4>;
dsi,channel = <0>;
enable-delay-ms = <35>;
prepare-delay-ms = <6>;
unprepare-delay-ms = <0>;
disable-delay-ms = <20>;
size,width = <120>;
size,height = <170>;
status = "okay";
...
power_ctr: power_ctr {
rockchip,debug = <0>;
lcd_pwr_en: lcd-pwr-en {
gpios = <&gpio3 16 GPIO_ACTIVE_HIGH>;
pinctrl-names = "default";
pinctrl-0 = <&lcd_panel_pwr_en>;
rockchip,delay = <10>;
};
lcd_rst: lcd-rst {
gpios = <&gpio2 27 GPIO_ACTIVE_HIGH>;
pinctrl-names = "default";
pinctrl-0 = <&lcd_panel_reset>;
rockchip,delay = <6>;
};
};
...
&pinctrl {
lcd-panel {
lcd_panel_reset: lcd-panel-reset {
rockchip,pins = <2 27 RK_FUNC_GPIO &pcfg_pull_down>;
};
lcd_panel_pwr_en: lcd-panel-pwr-en {
rockchip,pins = <3 16 RK_FUNC_GPIO &pcfg_pull_down>;
};
};
};
这里定义了LCD的电源控制引脚：
lcd_pwr_en:(GPIO3_C0)GPIO_ACTIVE_HIGH
lcd_rst:(GPIO2_D3)GPIO_ACTIVE_HIGH
都是高电平有效，具体的引脚配置请参考《GPIO》一节。
配置背光¶
AIO-3399J开发板外置了一个背光接口用来控制屏幕背光，如下图所示：
在DTS文件：kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-core.dtsi中配置了背光信息，如下：
/ {
compatible = "rockchip,rk3399-firefly-core", "rockchip,rk3399";
backlight: backlight {
status = "disabled";
compatible = "pwm-backlight";
pwms = <&pwm0 0 25000 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 99 100 101 102 103
104 105 106 107 108 109 110 111
112 113 114 115 116 117 118 119
120 121 122 123 124 125 126 127
128 129 130 131 132 133 134 135
136 137 138 139 140 141 142 143
144 145 146 147 148 149 150 151
152 153 154 155 156 157 158 159
160 161 162 163 164 165 166 167
168 169 170 171 172 173 174 175
176 177 178 179 180 181 182 183
184 185 186 187 188 189 190 191
192 193 194 195 196 197 198 199
200 201 202 203 204 205 206 207
208 209 210 211 212 213 214 215
216 217 218 219 220 221 222 223
224 225 226 227 228 229 230 231
232 233 234 235 236 237 238 239
240 241 242 243 244 245 246 247
248 249 250 251 252 253 254 255>;
default-brightness-level = <200>;
};
pwms属性：配置PWM，范例里面默认使用pwm0，25000ns是周期(40 KHz)。LVDS需要加背光电源控制脚，在kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-aio-lvds.dts中可以看到以下语句：
&backlight {
status = "okay";
enable-gpios = <&gpio1 1 GPIO_ACTIVE_HIGH>;
brightness-levels = < 150 151
152 153 154 155 156 157 158 159
160 161 162 163 164 165 166 167
168 169 170 171 172 173 174 175
176 177 178 179 180 181 182 183
184 185 186 187 188 189 190 191
192 193 194 195 196 197 198 199
200 201 202 203 204 205 206 207
208 209 210 211 212 213 214 215
216 217 218 219 220 221 222 223
224 225 226 227 228 229 230 231
232 233 234 235 236 237 238 239
240 241 242 243 244 245 246 247
248 249 250 251 252 253 254 255>;
};
因此使用时需修改DTS文件。
brightness-levels属性：配置背光亮度数组，最大值为255，配置暗区和亮区，并把亮区数组做255的比例调节。比如范例中暗区是255-221，亮区是220-0。 default-brightness-level属性：开机时默认背光亮度，范围为0-255。 具体请参考kernel中的说明文档：kernel/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
配置显示时序¶
与EDP屏不同，LVDS屏的 Timing 写在DTS文件中，在kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-aio-lvds.dts中可以看到以下语句：
disp_timings: display-timings {
native-mode = <&timing0>;
timing0: timing0 {
clock-frequency = <80000000>;
hactive = <768>;
vactive = <1024>;
hsync-len = <20>; //20, 50
hback-porch = <130>; //50, 56
hfront-porch = <150>;//50, 30
vsync-len = <40>;
vback-porch = <130>;
vfront-porch = <136>;
hsync-active = <0>;
vsync-active = <0>;
de-active = <0>;
pixelclk-active = <0>;
};
}
}
时序属性参考下图：
Init Code¶
lvds屏上完电后需要发送初始化指令才能使之工作。初始化指令需要以下工具文档生成，下载TC358764_5_774_5XBG_DSI-LVDS_Tv11p_nm_1280x800.xls
如何配置LVDS panel-init-sequence¶
以1280x800单lvds为例:
首先打开TC358764_5_774_5XBG_DSI-LVDS_Tv11p_nm_1280x800.xls
选择页面”Timing Parameters_SYNC_EVENT”，按照LVDS屏的时序填入LVDS timing黄色单元,一般只需填入以下单元即可。
HPW / HBPR / HDISPR / HFPR 分别对应 hsync-len / hback-porch / hactive / hfront-porch
VPW / VBPR / VDISPR / VFPR 分别对应 vhsync-len / vback-porch / vactive / vfront-porch
LVDS timing填入完成后还需配置常规参数
1.根据LVDS屏规格书确认LVDS Link和LVDS output format并选择屏的参数。
2.计算LVDS clock(蓝色单元无法写入，需要黄色单元自动计算得出)，需要填入DSI Clock(HOST), Pixel Clock Source, Pixel Clock Divider。计算公式如下:DSI Clock/Pixel Clock Source/Pixel Clock Divider=LVDS Clock
填入上述黄色单元基本上完成配置，接下来选择页面”Source”即可看到转换后的Comment
以上面为例”013C 00030005”，mipi command就应该是”29 02 06 3C 01 05 00 03 00”
29 : packet ID
02 : 2ms delay
06 : 6 bytes
3C 01 : address = 0x013C
00 03 00 05 : data=0x05000300
将页面source所有地址写入数据，即可完成初始化指令panel-init-sequence。
dts在kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-aio-lvds.dts中可以看到lvds的初始化指令列表：
&dsi {
status = "okay";
...
panel-init-sequence = [
29 00 06 3C 01 09 00 07 00
29 00 06 14 01 06 00 00 00
29 00 06 64 01 0B 00 00 00
29 00 06 68 01 0B 00 00 00
29 00 06 6C 01 0B 00 00 00
29 00 06 70 01 0B 00 00 00
29 00 06 34 01 1F 00 00 00
29 00 06 10 02 1F 00 00 00
29 00 06 04 01 01 00 00 00
29 00 06 04 02 01 00 00 00
29 00 06 50 04 20 01 F0 03
29 00 06 54 04 32 00 B4 00
29 00 06 58 04 80 07 48 00
29 00 06 5C 04 0A 00 19 00
29 00 06 60 04 38 04 0A 00
29 00 06 64 04 01 00 00 00
29 01 06 A0 04 06 80 44 00
29 00 06 A0 04 06 80 04 00
29 00 06 04 05 04 00 00 00
29 00 06 80 04 00 01 02 03
29 00 06 84 04 04 07 05 08
29 00 06 88 04 09 0A 0E 0F
29 00 06 8C 04 0B 0C 0D 10
29 00 06 90 04 16 17 11 12
29 00 06 94 04 13 14 15 1B
29 00 06 98 04 18 19 1A 06
29 02 06 9C 04 33 04 00 00
];
panel-exit-sequence = [
05 05 01 28
05 78 01 10
];
...
};
命令格式以及说明可参考以下附件： Rockchip DRM Panel Porting Guide.pdf
kernel 发送指令可以看到在kernel/drivers/gpu/drm/panel/panel-simple.c文件中的操作：
static int panel_simple_enable(struct drm_panel *panel)
{
struct panel_simple *p = to_panel_simple(panel);
int err;
if (p->enabled)
return 0;
DBG("enter\n");
if (p->on_cmds) {
err = panel_simple_dsi_send_cmds(p, p->on_cmds);
if (err)
dev_err(p->dev, "failed to send on cmds\n");
}
if (p->desc && p->desc->delay.enable) {
DBG("p->desc->delay.enable=%d\n", p->desc->delay.enable);
msleep(p->desc->delay.enable);
}
if (p->backlight) {
DBG("open backlight\n");
p->backlight->props.power = FB_BLANK_UNBLANK;
backlight_update_status(p->backlight);
}
p->enabled = true;
return 0;
}
u-boot
发送指令可以看到在u-boot/drivers/video/rockchip-dw-mipi-dsi.c文件中的操作：
static int rockchip_dw_mipi_dsi_enable(struct display_state *state)
{
struct connector_state *conn_state = &state->conn_state;
struct crtc_state *crtc_state = &state->crtc_state;
const struct rockchip_connector *connector = conn_state->connector;
const struct dw_mipi_dsi_plat_data *pdata = connector->data;
struct dw_mipi_dsi *dsi = conn_state->private;
u32 val;
DBG("enter\n");
dw_mipi_dsi_set_mode(dsi, DW_MIPI_DSI_VID_MODE);
dsi_write(dsi, DSI_MODE_CFG, ENABLE_CMD_MODE);
dw_mipi_dsi_set_mode(dsi, DW_MIPI_DSI_VID_MODE);
if (!pdata->has_vop_sel)
return 0;
if (pdata->grf_switch_reg) {
if (crtc_state->crtc_id)
val = pdata->dsi0_en_bit | (pdata->dsi0_en_bit << 16);
else
val = pdata->dsi0_en_bit << 16;
writel(val, RKIO_GRF_PHYS + pdata->grf_switch_reg);
}
debug("vop %s output to dsi0\n", (crtc_state->crtc_id) ? "LIT" : "BIG");
//rockchip_dw_mipi_dsi_read_allregs(dsi);
return 0;
}