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

[gaun]

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.

[gaun]

Hi Igor,

That is exactly what I did. I just commented out the 3300000 and added 2800000. The problem is that these regulator outputs are used by the CSI and DSI components which are clearly marked in the schematic as 2.8V but the output is 3.3V.

Thanks,

Gautam.

[igorpadykov]

Hi Gautam

this can be posted on uboot mail list

U-Boot Info Page 

for dts changes one can consider regulator-fixed as in  "vref-1v8" in imx7d-sdb.dts

linux-imx.git - i.MX Linux Kernel 

Best regards
igor
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