[ROC-RK3568-PC] [Firefly-Android] 10min带你了解LCD的使用

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• 🍇 专栏目录： 【Firefly-RK356x板卡】
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一、内核Config配置

ROC-RK3568-PC的SDK下kernel/arch/arm64/configs/firefly_defconfig已经把LCD相关的配置好：

CONFIG_DRM_ROCKCHIP=y
CONFIG_ROCKCHIP_DW_MIPI_DSI=y
CONFIG_DRM_PANEL_SIMPLE=y

二、MIPI配置

ROC-RK3568-PC的SDK有MIPI DSI的DTS文件： kernel/arch/arm64/boot/dts/rockchip/rk3568-firefly-roc-pc-mipi101_M101014_BE45_A1.dts，此DTS文件为MIPI_DSI0+HDMI屏配置，MIPI_DSI1 默认关闭。

2.1 引脚配置

从DTS文件中可以看到以下语句：

#include "rk3568-firefly-roc-pc.dtsi"/ {model = "ROC-RK3568-PC MIPI M101014_BE45_A1 + HDMI(Android)";compatible = "rockchip,rk3568-firefly-roc-pc-mipi", "rockchip,rk3568";...
}&route_dsi0 {status = "okay";logo,rotation = "logo_rotation_270"; //support rotation 90,180,270connect = <&vp1_out_dsi0>;
};&video_phy0 {status = "okay";
};&dsi0_in_vp0 {status = "disabled";
};&dsi0_in_vp1 {status = "okay";
};/** mipi_dphy0 needs to be enabled* when dsi0 is enabled*/
&dsi0 {status = "okay";//rockchip,lane-rate = <1000>;dsi0_panel: panel@0 {status = "okay";compatible = "simple-panel-dsi";reg = <0>;backlight = <&backlight>;enable-gpios = <&gpio0 RK_PC7 GPIO_ACTIVE_HIGH>;reset-gpios = <&gpio3 RK_PB5 GPIO_ACTIVE_LOW>;enable-delay-ms = <35>;prepare-delay-ms = <6>;reset-delay-ms = <25>;init-delay-ms = <55>;unprepare-delay-ms = <0>;disable-delay-ms = <20>;mipi-data-delay-ms = <200>;...panel-init-sequence = [//39 00 04 B9 83 10 2E// 15 00 02 CF FF05 78 01 1105 32 01 29//15 00 02 35 00];panel-exit-sequence = [05 00 01 2805 00 01 10];...};
};
...
&route_hdmi {status = "okay";connect = <&vp0_out_hdmi>;
};&hdmi {status = "okay";
};&hdmi_in_vp0 {status = "okay";
};&hdmi_in_vp1 {status = "disabled";
};
...

这里定义了LCD的控制引脚：

NAME	GPIO	GPIO ACTIVE
LCD_EN	GPIO0_C7	GPIO_ACTIVE_HIGH
LCD_RST	GPIO3_B5	GPIO_ACTIVE_LOW

在硬件信号上 LCD_EN 引脚高电平有效，而 LCD_RST 引脚是低电平有效。

2.2 背光配置

在DTS文件中配置了背光信息，如下：

    backlight: backlight {status = "okay";compatible = "pwm-backlight";enable-gpios = <&gpio3 RK_PB0 GPIO_ACTIVE_HIGH>;pwms = <&pwm4 0 50000 1>;brightness-levels = <60  60  60  61  61  61  62  6262  63  63  63  64  64  64  6565  65  66  66  66  67  67  6768  68  68  69  69  69  70  7070  71  71  71  72  72  72  7373  73  74  74  74  75  75  7576  76  76  77  77  77  78  7878  79  79  79  80  80  80  8181  81  82  82  82  83  83  8384  84  84  85  85  85  86  8686  87  87  87  88  88  88  8989  89  90  91  92  93  94  9596  97  98  99 100 101 102 103104 105 106 107 108 109 110 111112 113 114 115 116 117 118 119120 121 122 123 124 125 126 127128 129 130 131 132 133 134 135136 137 138 139 140 141 142 143144 145 146 147 148 149 150 151152 153 154 155 156 157 158 159160 161 162 163 164 165 166 167168 169 170 171 172 173 174 175176 177 178 179 180 181 182 183184 185 186 187 188 189 190 191192 193 194 195 196 197 198 199200 201 202 203 204 205 206 207208 209 210 211 212 213 214 215216 217 218 219 220 221 222 223224 225 226 227 228 229 230 231232 233 234 235 236 237 238 239240 241 242 243 244 245 246 247248 249 250 251 252 253 254 255>;default-brightness-level = <200>;};

• enable-gpios：背光使能脚，高电平有效。

• pwms属性：配置PWM，范例里面默认使用pwm4，50000ns是周期(20 KHz)，pwm为负极性。

• brightness-levels属性：配置背光亮度数组，一般以值 255 为一个 scale，当 PWM 设置为正极性时，从 0~255 表示背光为正极，占空比从 0%~100% 变化，255~0 为负极性，占空比从 100%~0% 变化；当 PWM 设置为负极性时，反之。

• default-brightness-level属性：开机时默认背光亮度，范围为0-255。

具体可参考kernel中的说明文档：kernel/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt

2.3 显示时序配置

2.3.1 Power on/off sequence

MIPI屏的上下电时序通常都在规格书的Power on/off sequence章节中，可根据规格书的上下电时序修改dts，panel节点中有如下属性:

&dsi0 {status = "okay";//rockchip,lane-rate = <1000>;dsi0_panel: panel@0 {status = "okay";compatible = "simple-panel-dsi";...enable-delay-ms = <35>;prepare-delay-ms = <6>;reset-delay-ms = <25>;init-delay-ms = <55>;unprepare-delay-ms = <0>;disable-delay-ms = <20>;mipi-data-delay-ms = <200>;...};
};

mipi-data-delay-ms为Firefly 10.1寸 M101014-BE45-A1 MIPI屏所需时序，调试屏幕时可根据本身上下电时序是否需要再配置此属性。MIPI上下电后需要发送初始化或退出指令才能使之正常工作，初始化和退出指令列表可以参考kernel/arch/arm64/boot/dts/rockchip/rk3568-firefly-roc-pc-mipi101_CZNB101862T.dts，列表如下：

&dsi0 {status = "okay";//rockchip,lane-rate = <1000>;dsi0_panel: panel@0 {...panel-init-sequence = [15 00 02 E0 0015 00 02 E1 9315 00 02 E2 6515 00 02 E3 F815 00 02 E0 0415 00 02 2D 03		15 00 02 E0 0015 00 02 80 03		//15 00 02 4A 35		15 00 02 E0 0115 00 02 00 00		15 00 02 E0 0115 00 02 4B 04//15 00 02 4A 35		15 00 02 00 0015 00 02 01 66//15 00 02 03 00		//15 00 02 04 6D15 00 02 17 00		15 00 02 18 AF15 00 02 19 01...];panel-exit-sequence = [05 05 01 2805 78 01 10];};
};

dts中的init-sequence和panel-exit-sequence，只是配置了上电和下电指令, 其他的初始化指令已经烧录在M101014-BE45-A1这款MIPI屏的IC里，dts无需配置。接下来来看看上下电时序在驱动中的实现， 具体实现在kernel/drivers/gpu/drm/panel/panel-simple.c中：

static int panel_simple_disable(struct drm_panel *panel)
{...if (p->backlight) {p->backlight->props.power = FB_BLANK_POWERDOWN;p->backlight->props.state |= BL_CORE_FBBLANK;backlight_update_status(p->backlight);}if (p->desc->delay.disable)panel_simple_sleep(p->desc->delay.disable);if (p->cmd_type == CMD_TYPE_MCU) {err = panel_simple_xfer_mcu_cmd_seq(p, p->desc->exit_seq);if (err)dev_err(panel->dev, "failed to send exit cmds seq\n");}...
}static int panel_simple_unprepare(struct drm_panel *panel)
{...if (p->desc->exit_seq) {if (p->dsi)panel_simple_xfer_dsi_cmd_seq(p, p->desc->exit_seq);else if (p->cmd_type == CMD_TYPE_SPI)err = panel_simple_xfer_spi_cmd_seq(p, p->desc->exit_seq);if (err)dev_err(panel->dev, "failed to send exit cmds seq\n");}gpiod_direction_output(p->reset_gpio, 1);if(!p->enable_on_always){gpiod_direction_output(p->enable_gpio, 0);}...
}static int panel_simple_prepare(struct drm_panel *panel)
{...gpiod_direction_output(p->enable_gpio, 1);if (p->desc->delay.prepare)panel_simple_sleep(p->desc->delay.prepare);...gpiod_direction_output(p->reset_gpio, 1);if (p->desc->delay.reset)panel_simple_sleep(p->desc->delay.reset);gpiod_direction_output(p->reset_gpio, 0);  //由于驱动在控制reset脚时序的时候使用了`gpiod`这类的API//如果在DTS配置了低电平有效，那么这里就会将reset引脚拉高，即取反。if (p->desc->delay.init)panel_simple_sleep(p->desc->delay.init);if (p->desc->init_seq) {if (p->dsi)panel_simple_xfer_dsi_cmd_seq(p, p->desc->init_seq);else if (p->cmd_type == CMD_TYPE_SPI)err = panel_simple_xfer_spi_cmd_seq(p, p->desc->init_seq);if (err)dev_err(panel->dev, "failed to send init cmds seq\n");}if(p->desc->delay.mipi_data){panel_simple_sleep(p->desc->delay.mipi_data);}...
}static int panel_simple_enable(struct drm_panel *panel)
{...if (p->cmd_type == CMD_TYPE_MCU) {err = panel_simple_xfer_mcu_cmd_seq(p, p->desc->init_seq);if (err)dev_err(panel->dev, "failed to send init cmds seq\n");}if (p->desc->delay.enable)panel_simple_sleep(p->desc->delay.enable);if (p->backlight) {p->backlight->props.state &= ~BL_CORE_FBBLANK;p->backlight->props.power = FB_BLANK_UNBLANK;backlight_update_status(p->backlight);}...
}

2.3.2 Display-Timings

display_timings在dts中定义：

    disp_timings0: display-timings {native-mode = <&dsi0_timing0>;dsi0_timing0: timing0 {clock-frequency = <72600000>;//<80000000>;hactive = <800>;//<768>;vactive = <1280>;hsync-len = <14>;   //20, 50,10hback-porch = <26>; //50, 56,10hfront-porch = <32>;//50, 30,180vsync-len = <8>;//4vback-porch = <20>;//4vfront-porch = <80>;//8hsync-active = <0>;vsync-active = <0>;de-active = <0>;pixelclk-active = <0>;};};

相关的参数一般可以在屏的规格书中找到，然后在kernel/drivers/gpu/drm/panel/panel-simple.c的panel_simple_probe中初始化了获取时序的函数。

static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
{...panel->base.funcs = &panel_simple_funcs;...
}
...
static const struct drm_panel_funcs panel_simple_funcs = {.loader_protect = panel_simple_loader_protect,.disable = panel_simple_disable,.unprepare = panel_simple_unprepare,.prepare = panel_simple_prepare,.enable = panel_simple_enable,.get_modes = panel_simple_get_modes,.get_timings = panel_simple_get_timings,
};
...

该函数在kernel/drivers/gpu/drm/panel/panel-simple.c中定义：

static int panel_simple_get_timings(struct drm_panel *panel, unsigned int num_timings, struct display_timing *timings)
{struct panel_simple *p = to_panel_simple(panel);unsigned int i;if (p->desc->num_timings < num_timings)num_timings = p->desc->num_timings;if (timings)for (i = 0; i < num_timings; i++)timings[i] = p->desc->timings[i];return p->desc->num_timings;
}

三、EDP配置

3.1 引脚配置

ROC-RK3568-PC的SDK有EDP的DTS文件：kernel/arch/arm64/boot/dts/rockchip/rk3568-firefly-roc-pc-edp_M156X40.dts，从该文件中我们可以看到以下语句：

    edp_panel: edp-panel {compatible = "simple-panel";status = "okay";power-supply = <&vcc3v3_lcd_edp>;enable-gpios = <&gpio3 RK_PC3 GPIO_ACTIVE_HIGH>;//bus-format = <MEDIA_BUS_FMT_RBG888_1X24>;		backlight = <&backlight>;...ports {panel_in_edp: endpoint {remote-endpoint = <&edp_out_panel>;};};};...
};&edp {status = "okay";hpd-gpios = <&gpio0 RK_PC2 GPIO_ACTIVE_HIGH>;force-hpd;ports {edp_out: port@1 {reg = <1>;#address-cells = <1>;#size-cells = <0>;edp_out_panel: endpoint@0 {reg = <0>;remote-endpoint = <&panel_in_edp>;};};};
};

这里定义了LCD的电源控制引脚：

NAME	GPIO	GPIO_ACTIVE
BL_EN	GPIO3_C3	GPIO_ACTIVE_HIGH
EDP_HPD	GPIO0_C2	GPIO_ACTIVE_HIGH

3.2 EDP背光配置

因为背光接口是公用的，所以可以参考上述MIPI的配置方法。

4.3.3. EDP显示时序配置
不同于MIPI屏，EDP屏对上下电时序没有那么高的要求，当然还是要看调试屏幕的上下电时序图来配置：

    edp_panel: edp-panel {compatible = "simple-panel";status = "okay";...display-timings {native-mode = <&timing0>;		timing0: timing0 {clock-frequency = <140000000>;hactive = <1920>;vactive = <1080>;hfront-porch = <40>;hsync-len = <40>;hback-porch = <80>;vfront-porch = <16>;vsync-len = <8>;vback-porch = <16>;hsync-active = <0>;vsync-active = <0>;de-active = <0>;pixelclk-active = <0>;};};...};

display-timings同样在kernel/drivers/gpu/drm/panel/panel-simple.c中使用到：

static int panel_simple_get_timings(struct drm_panel *panel, unsigned int num_timings, struct display_timing *timings)
{struct panel_simple *p = to_panel_simple(panel);unsigned int i;if (p->desc->num_timings < num_timings)num_timings = p->desc->num_timings;if (timings)for (i = 0; i < num_timings; i++)timings[i] = p->desc->timings[i];return p->desc->num_timings;
}