pm8909的adc內部架構如圖所示（參考《80-nn174-58_b_pmic_adc_software_user_guide.pdf》）：
mpp configuration就是在裝置樹里配置：
pm8909_mpps: mpps ;
};&pm8909_mpps ;
};採用通道0x13（就是19：p_mux4_1_1通道）註冊，這裡是必須要加的，否則讀這個通道出錯：
//stone added for mpp4 as adc
chan@13 ;
測試時，需要讀取p_mux4_1_1通道：
static int get_battery_voltage(struct qpnp_bms_chip *chip, int *result_uv)
//end: stone added for test
……如果需要測試0-5v的範圍，可以使用35通道，修改的地方只是通道註冊改為0x23，呼叫時用p_mux4_1_3即可。
參考補丁：
diff --git a/kernel/msm-3.18/arch/arm/boot/dts/msm-pm8909.dtsi b/kernel/msm-3.18/arch/arm/boot/dts/msm-pm8909.dtsi
index c3e402802a..12dc08e6fa 100755
--- a/kernel/msm-3.18/arch/arm/boot/dts/msm-pm8909.dtsi
+++ b/kernel/msm-3.18/arch/arm/boot/dts/msm-pm8909.dtsi
@@ -196,13 +196,14 @@
interrupts = <0x0 0x61 0x1>;
};};
-+ //stone added for mpp4 as adc
+ /*
qcom,leds@a300 ;
-+ */
pm8909_chg: qcom,charger ;
++ //stone added for mpp4 as adc
+ chan@23 ;
+ };
&pm8909_adc_tm ;
}; +//stone added for mpp4 as adc
+/* &spmi_bus ;
};};+*/
&sdc2_cd_on ;
- mpp@a300 ;
+*/+ mpp@a300 ;
+ };
&mdss_mdp
+ //end: stone added for debug
+ rc = qpnp_vadc_read(chip->vadc_dev, vbat_sns, &adc_result);
if (rc) {
pr_err("error reading adc channel = %d, rc = %d\n",