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开发板 ：NanoPC-T4开发板
eMMC ：16GB
LPDDR3 ：4GB
显示屏 ：15.6英寸HDMI接口显示屏
u-boot ：2023.04
linux ：6.3
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在《Rockchip RK3399 - DRM驱动程序》》我们已经介绍过了，RK3399有两个VOP，均可以支持HDMI、eDP、DP、MIPI DSI0、MIPI DSI1显示接口，由于此时我手里正好有一块友善7寸高清电容触摸显示屏（型号为HD702E，edp接口），因此本节我们选择edp作为分析的对象。
一、设备树配置
1.1 edp设备节点
设备节点vopb下的子节点vopb_out_edp通过edp_in_vopb（由remote-endpoint属性指定）和edp显示接口组成一个连接通路；
设备节点vopl下的子节点vopl_out_edp通过edp_in_vopl（由remote-endpoint属性指定）和edp显示接口组成一个连接通路；
edp: edp@ff970000 {
compatible = "rockchip,rk3399-edp";
reg = <0x0 0xff970000 0x0 0x8000>;
interrupts = <GIC_SPI 10 IRQ_TYPE_LEVEL_HIGH 0>;
clocks = <&cru PCLK_EDP>, <&cru PCLK_EDP_CTRL>, <&cru PCLK_VIO_GRF>;
clock-names = "dp", "pclk", "grf";
pinctrl-names = "default";
pinctrl-0 = <&edp_hpd>;
power-domains = <&power RK3399_PD_EDP>;
resets = <&cru SRST_P_EDP_CTRL>;
reset-names = "dp";
rockchip,grf = <&grf>;
status = "disabled";
ports {
#address-cells = <1>;
#size-cells = <0>;
edp_in: port@0 {
reg = <0>;
#address-cells = <1>;
#size-cells = <0>;
edp_in_vopb: endpoint@0 {
reg = <0>;
remote-endpoint = <&vopb_out_edp>;
};
edp_in_vopl: endpoint@1 {
reg = <1>;
remote-endpoint = <&vopl_out_edp>;
};
};
};
};
其中：
- 子节点
ports;- 2个
input endpoint，分别连接到VOPL和VOPB；也就是在rk3399上，eDP可以和VOPL、VOPB连接； - 1个
output endpoint连接到了epd panel上（这个下面介绍）;
- 2个
因此可以得到有2条同理：
vopb_out_edp--->edp_in_vopb；vopl_out_edp--->edp_in_vopl；edp_out_panel--->panel_in_edp；
需要注意的是，⼀个显⽰接口在同⼀个时刻只能和⼀个VOP连接，所以在具体的板级配置中，需要设备树中把要使⽤的通路打开，把不使⽤的通路设置为disabled状态。
1.2 启用edp
如果希望edp连接在vopl上，则需要在arch/arm64/boot/dts/rockchip/rk3399-evb.dts中为以下节点新增属性：
&display_subsystem {
status = "okay";
};
&vopl {
status = "okay";
};
&vopl_mmu {
status = "okay";
};
&edp {
status = "okay";
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>;
};
};
};
};
&edp_in_vopl{
status = "okay";
};
&edp_in_vopb{
status = "disabled";
};
同时配置设备节点panel_in_edp、backlight：
backlight: backlight {
compatible = "pwm-backlight";
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 = <&pwm0 0 25000 0>;
};
edp_panel: edp-panel {
compatible = "lg,lp079qx1-sp0v";
backlight = <&backlight>;
enable-gpios = <&gpio1 RK_PB5 GPIO_ACTIVE_HIGH>;
power-supply = <&vcc3v3_s0>;
port {
panel_in_edp: endpoint {
remote-endpoint = <&edp_out_panel>;
};
};
};
二、platfrom driver
在rockchip_drm_init函数中调用：
ADD_ROCKCHIP_SUB_DRIVER(rockchip_dp_driver,
CONFIG_ROCKCHIP_ANALOGIX_DP);
会将rockchip_dp_driver保存到rockchip_sub_drivers数组中。
并调用platform_register_drivers遍历rockchip_sub_drivers数组，多次调用platform_driver_register注册platform driver。
2.1 rockchip_dp_driver
rockchip_dp_driver定义在drivers/gpu/drm/rockchip/analogix_dp-rockchip.c；
struct platform_driver rockchip_dp_driver = {
.probe = rockchip_dp_probe,
.remove = rockchip_dp_remove,
.driver = {
.name = "rockchip-dp",
.pm = &rockchip_dp_pm_ops,
.of_match_table = rockchip_dp_dt_ids, // 用于设备树匹配
},
};
2.1.1 of_match_table
其中of_match_table用于设备树匹配，匹配设备树中compatible = "rockchip,rk3399-edp"的设备节点；
static const struct of_device_id rockchip_dp_dt_ids[] = {
{.compatible = "rockchip,rk3288-dp", .data = &rk3288_dp },
{.compatible = "rockchip,rk3399-edp", .data = &rk3399_edp },
{}
};
2.1.2 probe
在plaftrom总线设备驱动模型中，我们知道当内核中有platform设备和platform驱动匹配，会调用到platform_driver里的成员.probe，在这里就是rockchip_dp_probe函数；
static const struct component_ops rockchip_dp_component_ops = {
.bind = rockchip_dp_bind,
.unbind = rockchip_dp_unbind,
};
static int rockchip_dp_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
const struct rockchip_dp_chip_data *dp_data;
struct drm_panel *panel = NULL;
struct rockchip_dp_device *dp;
int ret;
dp_data = of_device_get_match_data(dev);
if (!dp_data)
return -ENODEV;
ret = drm_of_find_panel_or_bridge(dev->of_node, 1, 0, &panel, NULL);
if (ret < 0)
return ret;
dp = devm_kzalloc(dev, sizeof(*dp), GFP_KERNEL);
if (!dp)
return -ENOMEM;
dp->dev = dev;
dp->adp = ERR_PTR(-ENODEV);
dp->data = dp_data;
dp->plat_data.panel = panel;
dp->plat_data.dev_type = dp->data->chip_type;
dp->plat_data.power_on_start = rockchip_dp_poweron_start;
dp->plat_data.power_off = rockchip_dp_powerdown;
dp->plat_data.get_modes = rockchip_dp_get_modes;
ret = rockchip_dp_of_probe(dp);
if (ret < 0)
return ret;
platform_set_drvdata(pdev, dp);
dp->adp = analogix_dp_probe(dev, &dp->plat_data);
if (IS_ERR(dp->adp))
return PTR_ERR(dp->adp);
ret = component_add(dev, &rockchip_dp_component_ops);
if (ret)
goto err_dp_remove;
return 0;
err_dp_remove:
analogix_dp_remove(dp->adp);
return ret;
}
这里代码很简单，就是为设备pdev->dev向系统注册一个component，其中组件可执行的初始化操作被设置为了rockchip_dp_component_ops，我们需要重点关注bind函数的实现，这个我们单独小节介绍。
2.2 rockchip_dp_bind
rockchip_dp_bind函数定义在drivers/gpu/drm/rockchip/analogix_dp-rockchip.c，涉及到对edp设备节点的解析；
static int rockchip_dp_bind(struct device *dev, struct device *master,
void *data)
{
struct rockchip_dp_device *dp = dev_get_drvdata(dev);
struct drm_device *drm_dev = data;
int ret;
dp->drm_dev = drm_dev;
ret = rockchip_dp_drm_create_encoder(dp);
if (ret) {
DRM_ERROR("failed to create drm encoder\n");
return ret;
}
dp->plat_data.encoder = &dp->encoder.encoder;
ret = analogix_dp_bind(dp->adp, drm_dev);
if (ret)
goto err_cleanup_encoder;
return 0;
err_cleanup_encoder:
dp->encoder.encoder.funcs->destroy(&dp->encoder.encoder);
return ret;
}
2.2.1 rockchip_dp_drm_create_encoder
rockchip_dp_drm_create_encoder函数定义在drivers/gpu/drm/rockchip/analogix_dp-rockchip.c；
static int rockchip_dp_drm_create_encoder(struct rockchip_dp_device *dp)
{
struct drm_encoder *encoder = &dp->encoder.encoder;
struct drm_device *drm_dev = dp->drm_dev;
struct device *dev = dp->dev;
int ret;
encoder->possible_crtcs = drm_of_find_possible_crtcs(drm_dev,
dev->of_node);
DRM_DEBUG_KMS("possible_crtcs = 0x%x\n", encoder->possible_crtcs);
ret = drm_simple_encoder_init(drm_dev, encoder,
DRM_MODE_ENCODER_TMDS);
if (ret) {
DRM_ERROR("failed to initialize encoder with drm\n");
return ret;
}
drm_encoder_helper_add(encoder, &rockchip_dp_encoder_helper_funcs);
return 0;
}
2.2.2 analogix_dp_bind
analogix_dp_bind函数定义在drivers/gpu/drm/bridge/analogix/analogix_dp_core.c；
int analogix_dp_bind(struct analogix_dp_device *dp, struct drm_device *drm_dev)
{
int ret;
dp->drm_dev = drm_dev;
dp->encoder = dp->plat_data->encoder;
dp->aux.name = "DP-AUX";
dp->aux.transfer = analogix_dpaux_transfer;
dp->aux.dev = dp->dev;
dp->aux.drm_dev = drm_dev;
ret = drm_dp_aux_register(&dp->aux);
if (ret)
return ret;
pm_runtime_use_autosuspend(dp->dev);
pm_runtime_set_autosuspend_delay(dp->dev, 100);
pm_runtime_enable(dp->dev);
ret = analogix_dp_create_bridge(drm_dev, dp);
if (ret) {
DRM_ERROR("failed to create bridge (%d)\n", ret);
goto err_disable_pm_runtime;
}
return 0;
err_disable_pm_runtime:
pm_runtime_dont_use_autosuspend(dp->dev);
pm_runtime_disable(dp->dev);
drm_dp_aux_unregister(&dp->aux);
return ret;
}