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Problems with the VLDO4 having 3.3V instead of 2.8V output in the i.mx7D sabre board.

Question asked by Gautam Bhat on Jan 31, 2017
Latest reply on Feb 1, 2017 by Gautam Bhat

Hi,

 

When I was measuring the voltage input of the MIPI CSI and MIPI DSI Vcc input from the VLDO4 of the PMIC I found that the voltage is around 3.3V instead of 2.8V as shown in the schematic. After further analysis I found that there is no setting provided in the code i.e. u-boot and the kernel. The board I am using is the i.MX7D sabre development board.

 

Hence I modified the u-boot code and the kernel code:

 

u-boot:

 

In the power_init_board function add this at the end before return 0.

/* 
   Set the voltage for MIPI DSI
          input to 2.8V
*/

pmic_reg_read(p, PFUZE300_VLDO4CTL, &reg);
reg &= ~(0xF);
reg |= 0xA; /* Set to 2.8V */
pmic_reg_write(p, PFUZE300_VLDO4CTL, reg);

 

In the kernel modify the dtsi in the "vgen6_reg: vldo4" as follows:

vgen6_reg: vldo4 {
    regulator-min-microvolt = <1800000>;
    regulator-max-microvolt = <2800000>;
    /*regulator-max-microvolt = <3300000>;*/
    regulator-always-on;
};

Please correct me if I am wrong. Also please somebody update the code before it does damages to the peripheral.

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