5. LCD使用¶
5.1. Config配置¶
ITX-3568Q的SDK下kernel/arch/arm64/configs/firefly_defconfig已经把LCD相关的配置设置好了，如果自己做了修改，请注意把以下配置加上：
CONFIG_DRM_ROCKCHIP=y
CONFIG_ROCKCHIP_DW_MIPI_DSI=y
CONFIG_DRM_PANEL_SIMPLE=y
5.2. MIPI DTS配置¶
ITX-3568Q的SDK有MIPI DSI的DTS文件：
rk3568-firefly-itx-3568q-mipi101_M101014_BE45_A1.dts，此 DTS 文件为 MIPI_DSI1+HDMI 屏配置，MIPI_DSI0 默认关闭，接下来以此 DTS 中的 DSI1 配置作为范例来进行相关的 LCD 驱动介绍。
5.2.1. VP 分配¶
从DTS文件中我们可以看到以下语句：
&route_dsi0 {
status = "disabled";
connect = <&vp1_out_dsi0>;
};
&video_phy0 {
status = "disabled";
};
&dsi0_in_vp0 {
status = "disabled";
};
&dsi0_in_vp1 {
status = "disabled";
};
&dsi0 {
status = "disabled";
};
&route_dsi1 {
status = "okay";
connect = <&vp1_out_dsi1>;
};
&video_phy1 {
status = "okay";
};
&dsi1_in_vp0 {
status = "disabled";
};
&dsi1_in_vp1 {
status = "okay";
};
&route_hdmi {
status = "okay";
connect = <&vp0_out_hdmi>;
};
&hdmi {
status = "okay";
};
&hdmi_in_vp0 {
status = "okay";
};
&hdmi_in_vp1 {
status = "disabled";
};
vp 是视频接口的意思，这一段表示 DSI0 关闭，DSI1 开启并使用 vp1，HDMI 开启并使用 vp0
DSI1 和 HDMI 交换 vp 也是可以的，要保证不同的屏幕需要使用不同的 vp
5.2.2. 引脚配置¶
/*
* mipi_dphy1 needs to be enabled
* when dsi1 is enabled
*/
&dsi1 {
status = "okay";
//rockchip,lane-rate = <1000>;
dsi1_panel: panel@0 {
status = "okay";
compatible = "simple-panel-dsi";
reg = <0>;
backlight = <&backlight>;
enable-gpios = <&pca9555 PCA_IO1_2 GPIO_ACTIVE_HIGH>;
reset-gpios = <&gpio0 RK_PB0 GPIO_ACTIVE_LOW>;
pinctrl-names = "default";
pinctrl-0 = <&lcd_panel_reset>;
//power-supply = <&vcc1v8_lcd0_power>;
......
&pinctrl {
lcd {
lcd_panel_reset: lcd-panel-reset {
rockchip,pins = <0 RK_PB0 RK_FUNC_GPIO &pcfg_pull_none>;
};
};
};
这里定义了LCD的控制引脚：
| NAME | GPIO | GPIO_ACTIVE |
|---|---|---|
| enable-gpios(LCD_EN) | PCA_IO1_2 | GPIO_ACTIVE_HIGH |
| reset-gpios(LCD_RST) | GPIO0_B0 | 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，具体的引脚配置请参考《GPIO 使用》一节。需要注意的是ITX-3568Q的dsi1中，LCD_EN:(PCA_IO1_2)使用的是PCA9555扩展芯片引出来的gpio，需要PCA9555 驱动起来以后才能控制该gpio。
5.2.3. 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 = <&pca9555 PCA_IO0_6 GPIO_ACTIVE_HIGH>;
pwms = <&pwm4 0 50000 1>;
brightness-levels = <
60 60 60 61 61 61 62 62
62 63 63 63 64 64 64 65
65 65 66 66 66 67 67 67
......
......
>;
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。
具体请参考kernel中的说明文档：kernel/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
5.2.4. 显示时序配置¶
5.2.4.1. 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:
&dsi1 {
status = "okay";
//rockchip,lane-rate = <1000>;
dsi1_panel: panel@1 {
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，列表如下：
&dsi1 {
status = "okay";
//rockchip,lane-rate = <1000>;
dsi1_panel: panel@1 {
...
panel-init-sequence = [
//39 00 04 B9 83 10 2E
// 15 00 02 CF FF
05 78 01 11
05 32 01 29
//15 00 02 35 00
];
panel-exit-sequence = [
05 00 01 28
05 00 01 10
];
...
};
};
范例 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。接下来我们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);
}
...
}
uboot实现在u-boot/drivers/video/drm/rockchip_panel.c中的panel_simple_unprepare、panel_simple_prepare、panel_simple_enable
、panel_simple_disable 4个函数中，具体实现可以自己查看。
5.2.4.2. Display-Timings¶
display_timings在dts中定义：
disp_timings1: display-timings {
native-mode = <&dsi1_timing0>;
dsi1_timing0: timing0 {
clock-frequency = <72600000>;//<80000000>;
hactive = <800>;//<768>;
vactive = <1280>;
hsync-len = <14>; //20, 50,10
hback-porch = <26>; //50, 56,10
hfront-porch = <32>;//50, 30,180
vsync-len = <8>;//4
vback-porch = <20>;//4
vfront-porch = <80>;//8
hsync-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，如下在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;
}
详细说明可参考以下附件： Rockchip DRM Panel Porting Guide.pdf