LCD使用

簡介

AIO-3399J開發板外置了兩個LCD屏接口，一個是EDP，一個是LVDS，接口對應板子上的位置如下圖：

Config配置

以Android7.1為例，由于使用的是mipi轉lvds，AIO-3399J默認的配置文件kernel/arch/arm64/configs/firefly_defconfig已經把LCD相關的配置設置好了，如果自己做了修改，請注意把以下配置加上：

CONFIG_LCD_MIPI=y CONFIG_MIPI_DSI=y CONFIG_RK32_MIPI_DSI=y

DTS配置

引腳配置

LVDS屏

AIO-3399J的SDK有LVDS DSI的DTS文件：kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-aio-lvds.dts，從該文件中我們可以看到以下語句：

/ { 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 = ; //bus-format = ; 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>; }; }; };

這里定義了LCD的電源控制引腳：

lcd_pwr_en:(GPIO3_C0)GPIO_ACTIVE_HIGH lcd_rst:(GPIO2_D3)GPIO_ACTIVE_HIGH

都是高電平有效，具體的引腳配置請參考《GPIO》一節。

配置背光

AIO-3399J開發板外置了一個背光接口用來控制屏幕背光，如下圖所示：

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屬性：配置PWM，范例里面默認使用pwm0，25000ns是周期(40 KHz)。LVDS需要加背光電源控制腳，在kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-aio-lvds.dts中可以看到以下語句：

&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>; };

因此使用時需修改DTS文件。

brightness-levels屬性：配置背光亮度數組，最大值為255，配置暗區和亮區，并把亮區數組做255的比例調節。比如范例中暗區是255-221，亮區是220-0。 default-brightness-level屬性：開機時默認背光亮度，范圍為0-255。 具體請參考kernel中的說明文檔：kernel/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt

配置顯示時序

LVDS屏

與EDP屏不同，LVDS屏的 Timing 寫在DTS文件中，在kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-aio-lvds.dts中可以看到以下語句：

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>; }; } }

時序屬性參考下圖：

Init Code

LVDS屏

lvds屏上完電后需要發送初始化指令才能使之工作。

dts 可以在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 ]; ... };

命令格式以及說明可參考以下附件： Rockchip DRM Panel Porting Guide.pdf

kernel 發送指令可以看到在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 發送指令可以看到在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; }