LCD使用

简介

AIO-3399J开发板外置了两个LCD屏接口,一个是EDP,一个是LVDS,接口对应板子上的位置如下图:

_images/lcd_interface.jpg

LVDS屏

Config配置

以Android7.1为例,由于使用的是mipi转lvds,AIO-3399J默认的配置文件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_LCD_MIPI=y
CONFIG_MIPI_DSI=y
CONFIG_RK32_MIPI_DSI=y

DTS配置

引脚配置

AIO-3399J的SDK有LVDS DSI的DTS文件:kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-aio-lvds.dts,从该文件中我们可以看到以下语句:

/ {
    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 = <MIPI_DSI_FMT_RGB888>;
        //bus-format = <MEDIA_BUS_FMT_RGB666_1X18>;
        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>;
        };

    };
};

这里定义了LCD的电源控制引脚:

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

都是高电平有效,具体的引脚配置请参考《GPIO》一节。

配置背光

AIO-3399J开发板外置了一个背光接口用来控制屏幕背光,如下图所示:

_images/lcd_back_light.jpg

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属性:配置PWM,范例里面默认使用pwm0,25000ns是周期(40 KHz)。LVDS需要加背光电源控制脚,在kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-aio-lvds.dts中可以看到以下语句:

&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>;
};

因此使用时需修改DTS文件。

brightness-levels属性:配置背光亮度数组,最大值为255,配置暗区和亮区,并把亮区数组做255的比例调节。比如范例中暗区是255-221,亮区是220-0。 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

配置显示时序

与EDP屏不同,LVDS屏的 Timing 写在DTS文件中,在kernel/arch/arm64/boot/dts/rockchip/rk3399-firefly-aio-lvds.dts中可以看到以下语句:

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>;
           };
    }
}

时序属性参考下图:

_images/lcd_sequence.jpg

Init Code

lvds屏上完电后需要发送初始化指令才能使之工作。初始化指令需要以下工具文档生成,下载TC358764_5_774_5XBG_DSI-LVDS_Tv11p_nm_1280x800.xls

如何配置LVDS panel-init-sequence

以1280x800单lvds为例: 首先打开TC358764_5_774_5XBG_DSI-LVDS_Tv11p_nm_1280x800.xls _images/page.png 选择页面”Timing Parameters_SYNC_EVENT”,按照LVDS屏的时序填入LVDS timing黄色单元,一般只需填入以下单元即可。

  • HPW / HBPR / HDISPR / HFPR 分别对应 hsync-len / hback-porch / hactive / hfront-porch

  • VPW / VBPR / VDISPR / VFPR 分别对应 vhsync-len / vback-porch / vactive / vfront-porch

LVDS timing填入完成后还需配置常规参数 _images/parameter.png

  • 1.根据LVDS屏规格书确认LVDS Link和LVDS output format并选择屏的参数。

  • 2.计算LVDS clock(蓝色单元无法写入,需要黄色单元自动计算得出),需要填入DSI Clock(HOST), Pixel Clock Source, Pixel Clock Divider。计算公式如下:DSI Clock/Pixel Clock Source/Pixel Clock Divider=LVDS Clock

填入上述黄色单元基本上完成配置,接下来选择页面”Source”即可看到转换后的Comment _images/source.png 以上面为例”013C 00030005”,mipi command就应该是”29 02 06 3C 01 05 00 03 00”

  • 29 : packet ID

  • 02 : 2ms delay

  • 06 : 6 bytes

  • 3C 01 : address = 0x013C

  • 00 03 00 05 : data=0x05000300

将页面source所有地址写入数据,即可完成初始化指令panel-init-sequence。

dts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
            ];
        ...
};

命令格式以及说明可参考以下附件: Rockchip DRM Panel Porting Guide.pdf

  • kernel 发送指令可以看到在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

发送指令可以看到在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;
}

常见问题

1. 画面抖动闪屏

排查屏参数是否超出屏规格书限定周期,排查屏时钟大小。”Timing Parameters_SYNC_EVENT”所有参数变动必须和comment同步调整。

2. 颜色显示异常

尝试同步调整color mapping或者lvds timing。

NOTE: 页面”How to use”有详细步骤,其他参数说明可以参考文档”页面”菜单。