SC60 Android开发板
SC60的背光使用PM_MPP4输出PWM信号来控制背光芯片：
但是PMU的MPP4脚默认并不是PWM功能，需要修改配置。PWM的设备树节点为：
pm8953_pwm: qcom,pwms@bc00 {
status = "Okay";
compatible = "qcom,qpnp-pwm";
reg = <0xbc00 0x100>;
reg-names = "qpnp-lpg-channel-base";
qcom,channel-id = <0>;
qcom,supported-sizes = <6>, <9>;
#pwm-cells = <2>;
qcom,dtest-line = <2>; // notice: pwm need config DTETS2
qcom,dtest-output = <2>;
};
如下修改把MPP4配置为数字输出功能：
&pm8953_mpps {
/delete-node/ case_therm;
//begin: stone mofify mpp4 for lcd-backlight
mpp@a300 {
reg = <0xa300 0x100>;
com,pin-num = <4>; /*管脚号*/
qcom,mode = <1>; /* Digital output */
qcom,invert = <0>; /* Disable invert */
qcom,src-sel = <5>; /* DTEST2 ？？ */
qcom,pull = <1>;
qcom,vin-sel = <3>; /* VPH_PWR */
qcom,master-en = <1>; /* Enable MPP */
status = "okay";
};
//end: stone mofify mpp4 for lcd-backlight
};
这样，在对应的LCD驱动中指定PWM的管脚即可：
&dsi_lead_ili9885a_1080p_video{
qcom,mdss-dsi-panel-timings-phy-v2 = [23 1e 08 09 05 03 04 a0
23 1e 08 09 05 03 04 a0
23 1e 08 09 05 03 04 a0
23 1e 08 09 05 03 04 a0
23 1e 08 09 05 03 04 a0];
//qcom,esd-check-enabled;
qcom,mdss-dsi-panel-status-check-mode = "reg_read";
qcom,mdss-dsi-panel-status-command = [06 01 00 01 00 00 02 0a];
qcom,mdss-dsi-panel-status-command-state = "dsi_hs_mode";
qcom,mdss-dsi-panel-status-value = <0x08>;
qcom,mdss-dsi-panel-on-check-value = <0x08>;
qcom,mdss-dsi-panel-status-read-length = <2>;
qcom,mdss-dsi-panel-max-error-count = <3>;
qcom,display-id = "secondary";
qcom,panel-supply-entries = <&dsi_panel_pwr_supply>;
qcom,mdss-dsi-bl-pmic-control-type = "bl_ctrl_pwm";
qcom,mdss-dsi-bl-pmic-pwm-frequency = <25>;
qcom,mdss-dsi-bl-pmic-bank-select = <0>;
qcom,mdss-dsi-pwm-gpio = <&pm8953_mpps 4 0>; //这里指定PWM管脚MPP4
qcom,5v-boost-gpio = <&tlmm 0 0>;
};
在驱动kernel\msm-4.9\drivers\video\fbdev\msm\mdss_dsi_panel.c中会去获取这个节点的。
tmp = of_get_named_gpio(np,
"qcom,mdss-dsi-pwm-gpio", 0);
ctrl_pdata->pwm_pmic_gpio = tmp;
要注意，8953上默认是把MPP4脚作为温度采样功能配置了，需要修改掉：
case_therm {
cas_therm_default: cas_therm_default {
pins = "mpp4";
function = "analog";
input-enable;
qcom,amux-route = <3>;
};
};
chan@13 {
label = "case_therm";
reg = <0x13>;
qcom,decimation = <0>;
qcom,pre-div-channel-scaling = <0>;
qcom,calibration-type = "ratiometric";
qcom,scale-function = <2>;
qcom,hw-settle-time = <2>;
qcom,fast-avg-setup = <0>;
qcom,vadc-thermal-node;
};
如果要在LK阶段打开PWM，参考如下代码修改LK中的背光函数即可：
lk/project/msm8953.mk
-#ENABLE_PWM_SUPPORT := true
+ENABLE_PWM_SUPPORT := true
lk/target/msm89xx/target_display.c
static int pwm_backlight_ctrl(uint8_t enable)
{
+//begin: stone added for pm8953-mpp4 as lcd-backlight
+#ifdef FEATURE_SC60
+ struct pm8x41_mpp mpp;
+ int rc;
+
+ mpp.base = PM8x41_MMP4_BASE;
+ mpp.vin = MPP_VIN3;
+
+ if(enable) {
+ pm_pwm_enable(false);
+ rc = pm_pwm_config(PWM_DUTY_US, PWM_PERIOD_US);
+ if (rc < 0)
+ mpp.mode = MPP_HIGH;
+ else {
+ mpp.mode = MPP_DTEST2;
+ pm_pwm_enable(true);
+ }
+ pm8x41_config_output_mpp(&mpp);
+ pm8x41_enable_mpp(&mpp, MPP_ENABLE);
+ //pm8x41_reg_write(0x1BCD0, 0xA5);
+ //pm8x41_reg_write(0x1BCE3, 0x02);//notic: config pwm choose dtest2
+ } else {
+ pm_pwm_enable(false);
+ pm8x41_enable_mpp(&mpp, MPP_DISABLE);
+ }
+ mdelay(20);
+#else
……
#endif
｝