通常情况下lcm的avdd默认5.4v，某些屏幕对avdd要求不同，需要进行修改

驱动程序路径：

kernel-4.14/drivers/misc/mediatek/lcm/lcm_pmic.c

int display_bias_enable(void)
{int ret = 0;int retval = 0;display_bias_regulator_init();/* set voltage with min & max*/ret = regulator_set_voltage(disp_bias_pos, 5800000, 5800000);//修改avdd峰值if (ret < 0)pr_info("set voltage disp_bias_pos fail, ret = %d\n", ret);retval |= ret;ret = regulator_set_voltage(disp_bias_neg, 5800000, 5800000);//修改avee峰值if (ret < 0)pr_info("set voltage disp_bias_neg fail, ret = %d\n", ret);retval |= ret;
.........

修改后效果如下：

         我们可以明显的看到，AVDD拉高后有一个阶梯，分别为5.4v和5.8v，那是因为在启动时lk里的电压设置没有修改，导致在lk中AVDD峰值为5.4v，启动后峰值为5.8v；

lk程序路径：

vendor/mediatek/proprietary/bootable/bootloader/lk/dev/lcm/lcm_pmic.c

int display_bias_enable(void)
{int ret = 0;/*config rt5081 register 0xB2[7:6]=0x3, that is set db_delay=4ms.*/ret = PMU_REG_MASK(0xB2, (0x3 << 6), (0x3 << 6));/* set AVDD 5.4v, (4v+28*0.05v) *//*ret = RT5081_write_byte(0xB3, (1 << 6) | 28);*/
//修改avdd 5.8v,(4v+36*0.05v)ret = PMU_REG_MASK(0xB3, 36, (0x3F << 0));if (ret < 0)LCM_LOGI("nt35695----tps6132----cmd=%0x--i2c write error----\n", 0xB3);elseLCM_LOGI("nt35695----tps6132----cmd=%0x--i2c write success----\n", 0xB3);/* set AVEE *//*ret = RT5081_write_byte(0xB4, (1 << 6) | 28);*/ret = PMU_REG_MASK(0xB4, 36, (0x3F << 0));if (ret < 0)LCM_LOGI("nt35695----tps6132----cmd=%0x--i2c write error----\n", 0xB4);elseLCM_LOGI("nt35695----tps6132----cmd=%0x--i2c write success----\n", 0xB4);
.............

修改后效果如下：