RK3399 Android7.1调试LT9211

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最新推荐文章于 2025-03-07 10:52:10 发布

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分类专栏： # RK3399 Android7.1问题和解决方案文章标签： LT9211 MIPI转LVDS 显示

本文链接：https://blog.youkuaiyun.com/u011774634/article/details/131459889

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文章详细介绍了如何使用LT9211芯片在RK3399平台上实现MIPI到LVDS的转换，包括DTS配置、内核驱动代码和uboot驱动的添加。在调试过程中，解决了屏幕唤醒慢、图像抖动和开机不显示等问题，主要通过优化LT9211的寄存器配置和确保驱动在启动流程中的正确加载顺序。

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LT9211是龙讯的一款MIPI转LVDS的芯片，因RK3399没有LVDS接口，所以使用这颗芯片用来接LVDS的显示屏。连接关系简化如下：

对RK3399主控来讲，LT9211就相当于是一款MIPI显示屏，所以我们设置屏参的时候就是按照MIPI屏的配置修改DTS的。如下：

&dsi {
   status = "okay";
   rockchip,lane-rate = <500>;
   panel@0 {
       compatible ="simple-panel-dsi";
       reg = <0>;
       backlight = <&backlight>;
   enable-gpios = <&gpio3 2 GPIO_ACTIVE_HIGH>;
       reset-gpios = <&gpio3 0 GPIO_ACTIVE_HIGH>;
dsi,flags = <(MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_BURST |
                  MIPI_DSI_MODE_LPM | MIPI_DSI_MODE_EOT_PACKET)>;//NG
       dsi,format = <MIPI_DSI_FMT_RGB888>;
       dsi,lanes = <4>;
       status = "okay";
       prepare-delay-ms = <20>;
       reset-delay-ms = <20>;
       init-delay-ms = <20>;
       enable-delay-ms = <20>;
       disable-delay-ms = <20>;
       unprepare-delay-ms = <120>;
        display-timings {
           native-mode = <&timing1>;

           timing1: timing1 {
               clock-frequency = <69000000>;
               hactive = <1280>;
               vactive = <800>;
               hback-porch = <20>;
               hfront-porch = <40>;
               vback-porch = <12>;
               vfront-porch = <24>;
               hsync-len = <8>;
               vsync-len = <10>;
               de-active = <0>;
                hsync-active = <0>;
                vsync-active = <0>;
               pixelclk-active = <0>;
           };
       };
   };
};

另外，内核中需要添加LT9211的驱动代码，LT9211通过i2c与RK3399主控进行通信，驱动中的主要内容就是对LT9211的寄存器进行配置，对它初始化，让它可以将输入的MIPI信号转为LVDS信号点亮屏幕。驱动中的主要内容如下：

void lt9211_init(struct i2c_client *client)

{

LT9211_ChipID(client);

LT9211_SystemInt(client);

LT9211_MipiRxPhy(client);

LT9211_MipiRxDigital(client);

LT9211_TimingSet(client);

LT9211_MipiRxPll(client);

LT9211_MipiPcr(client);

LT9211_TxDigital(client);

LT9211_TxPhy(client);

#if LT9211_OUTPUT_PATTERN

LT9211_Pattern(&video_1280x800_60Hz,client);

#endif

mdelay(10);

LT9211_Txpll(client);

LT9211_RXCSC(client);

LT9211_ClockCheckDebug(client);

LT9211_VideoCheckDebug(client);

LT9211_BT_Set(client);

}

在每次点屏的时候都会跑这个初始化函数，具体位置如下：

static void dw_mipi_dsi_encoder_enable(struct drm_encoder *encoder)

{

struct dw_mipi_dsi *dsi = encoder_to_dsi(encoder);

unsigned long lane_rate = dw_mipi_dsi_get_lane_rate(dsi);

if (dsi->dphy.phy)

dw_mipi_dsi_set_hs_clk(dsi, lane_rate);

else

dw_mipi_dsi_set_pll(dsi, lane_rate);

dev_info(dsi->dev, "final DSI-Link bandwidth: %u x %d Mbps\n",

dsi->lane_mbps, dsi->slave ? dsi->lanes * 2 : dsi->lanes);

dw_mipi_dsi_vop_routing(dsi);

dw_mipi_dsi_pre_enable(dsi);

if (dsi->panel)

drm_panel_prepare(dsi->panel);

dw_mipi_dsi_enable(dsi);

if (dsi->panel)

drm_panel_enable(dsi->panel);

printk("dw_mipi_dsi lt9211_init\n");

msleep(100);

lt9211_init(g_client_lt9211);

}

除内核中添加LT9211驱动代码外，uboot中也需要添加LT9211的代码，驱动代码内容是一样的，只需要按照uboot驱动的编写格式移植到uboot中就行了。uboot中lt9211_init函数的具体位置如下：

static int display_enable(struct display_state *state)

{

const struct rockchip_connector *conn = state->conn_state.connector;

const struct rockchip_crtc *crtc = state->crtc_state.crtc;

const struct rockchip_connector_funcs *conn_funcs = conn->funcs;

const struct rockchip_crtc_funcs *crtc_funcs = crtc->funcs;

int ret = 0;

display_init(state);

if (!state->is_init)

return -EINVAL;

if (state->is_enable)

return 0;

if (crtc_funcs->prepare) {

ret = crtc_funcs->prepare(state);

if (ret)

return ret;

}

if (conn_funcs->prepare) {

ret = conn_funcs->prepare(state);

if (ret)

goto unprepare_crtc;

}

rockchip_panel_prepare(state);

if (crtc_funcs->enable) {

ret = crtc_funcs->enable(state);

if (ret)

goto unprepare_conn;

}

if (conn_funcs->enable) {

ret = conn_funcs->enable(state);

if (ret)

goto disable_crtc;

}

lt9211_init();

rockchip_panel_enable(state);

state->is_enable = true;

return 0;

unprepare_crtc:

if (crtc_funcs->unprepare)

crtc_funcs->unprepare(state);

unprepare_conn:

if (conn_funcs->unprepare)

conn_funcs->unprepare(state);

disable_crtc:

if (crtc_funcs->disable)

crtc_funcs->disable(state);

return ret;

}

调试中遇到的问题：

1，熄屏后按电源键唤醒屏幕显示很慢（约2秒钟），且在唤醒瞬间有时会有条纹状闪现。

解决：修改LT9211_MipiPcr的寄存器配置，改为如下配置：

void LT9211_MipiPcr(struct i2c_client *client)

{

u8 loopx;

u8 pcr_m;

LT9211_mipi_write(client,0xff,0xd0);

LT9211_mipi_write(client,0x0c,0x60);

LT9211_mipi_write(client,0x1c,0x60);

LT9211_mipi_write(client,0x24,0x70);

LT9211_mipi_write(client,0x2d,0x30);

LT9211_mipi_write(client,0x31,0x01);

/*stage1 hs mode*/

LT9211_mipi_write(client,0x25,0xd0);

LT9211_mipi_write(client,0x2a,0x30);

LT9211_mipi_write(client,0x21,0x4f);

LT9211_mipi_write(client,0x22,0x00);

/*stage2 hs mode*/

LT9211_mipi_write(client,0x1e,0x01);

LT9211_mipi_write(client,0x23,0x80);

/*stage2 de mode*/

LT9211_mipi_write(client,0x0a,0x02);

LT9211_mipi_write(client,0x38,0x02);

LT9211_mipi_write(client,0x39,0x04);

LT9211_mipi_write(client,0x3a,0x08);

LT9211_mipi_write(client,0x3b,0x10);

LT9211_mipi_write(client,0x3f,0x04);

LT9211_mipi_write(client,0x40,0x08);

LT9211_mipi_write(client,0x41,0x10);

LT9211_mipi_write(client,0x42,0x20);

LT9211_mipi_write(client,0x2b,0xa0);

LT9211_mipi_write(client,0xff,0xd0);

pcr_m = LT9211_read(client,0x26);

pcr_m &= 0x7f;

LT9211_mipi_write(client,0x26,pcr_m);

LT9211_mipi_write(client,0x27,0x0f);

LT9211_mipi_write(client,0xff,0x81);

LT9211_mipi_write(client,0x20,0xbf);

LT9211_mipi_write(client,0x20,0xff);

msleep(5);

LT9211_mipi_write(client,0x0B,0x6F);

LT9211_mipi_write(client,0x0B,0xFF);

msleep(100);//800->120

{

for(loopx = 0; loopx < 20; loopx++)

{

msleep(100);

LT9211_mipi_write(client,0xff,0xd0);

if(LT9211_read(client,0x87)&0x08)

{

printk("\r\nLT9211 pcr stable\n");

break;

}

else

{

printk("\r\nLT9211 pcr unstable!!!!");

}

LT9211_mipi_write(client,0xff,0xd0);

printk("LT9211 pcr_stable_M=%x\n",(LT9211_read(client,0x94)&0x7F));//打印M值

}

2，点亮屏幕后概率性图像剧烈抖动

原因：实际使用的为单LVDS屏，LT9211寄存器配置为双LVDS屏

解决：修改寄存器配置，如下：

LT9211_TxDigital函数中修改如下：

if( LT9211_OutPutModde == OUTPUT_LVDS_2_PORT )

{

LT9211_mipi_write( client,0x5c,0x01);

}

else

{

LT9211_mipi_write( client,0x5c,0x00);

}

和LT9211_TxPhy函数中修改如下：

if(LT9211_OutPutModde == OUTPUT_LVDS_2_PORT)

{

LT9211_mipi_write( client,0x3b,0xb8);

}

else

{

LT9211_mipi_write( client,0x3b,0x38);

}

3，开机概率性不显示，日志打印可看出有如下打印：

[ 1.589547] LT9211 pcr unstable!!!!
[ 1.589547] LT9211 pcr unstable!!!!
[ 1.589547] LT9211 pcr unstable!!!!
[ 1.589547] LT9211 pcr unstable!!!!
[ 1.589547] LT9211 pcr unstable!!!!
[ 1.589547] LT9211 pcr unstable!!!!
[ 1.589547] LT9211 pcr unstable!!!!
[ 1.589547] LT9211 pcr unstable!!!!
[ 2.637270] LT9211 pcr unstable!!!!
[ 2.637270] LT9211 pcr unstable!!!!LT9211 pcr_stable_M=24

原因：MIPI信号时序不对

解决：之前只在内核中加载了LT9211驱动，也就是lt9211_init执行的较晚。解决方法就是在uboot中也添加lt9211驱动。