What will occur when setting i.mx6ull VDD_SOC_CAP at 900MHz 1.175V (Old datasheet value)?

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What will occur when setting i.mx6ull VDD_SOC_CAP at 900MHz 1.175V (Old datasheet value)?

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935 Views
shaot
Contributor II

Hi, I use i.mx6ull and Yocto Morty.

Actually I noticed that fsl,soc-operating-points (VDD_SOC_CAP) is 1.175V at 900MHz in my device tree.

(refer to https://github.com/varigit/linux-imx/commit/c27010d99a3d91703ea2d1a3f9630a9dedc3f86f)

 

my device tree

cpu0: cpu@0 {
			compatible = "arm,cortex-a7";
			device_type = "cpu";
			reg = <0>;
			clock-latency = <61036>; /* two CLK32 periods */
			operating-points = <
				/* kHz	uV */
				900000	1275000
				792000	1225000
				528000	1175000
				396000	1025000
				198000	950000
			>;
			fsl,soc-operating-points = <
				/* KHz	uV */
				900000	1175000
				792000	1175000
				528000	1175000
				396000	1175000
				198000	1175000
			>;

datasheet (old)

(See attached i.mx6ull_datasheet_old.png)

 

However I found that fsl,soc-operating-points (VDD_SOC_CAP) should be 1.25V because 1.175V is old datasheet value and was updated in the latest kernel. (refer to https://github.com/varigit/linux-imx/commit/c3e4be705852c6d973d3b1f2b8b024fdea7303af)

dts (should be updated to this)

fsl,soc-operating-points = <
				/* KHz	uV */
				900000	1250000
				792000	1175000
				528000	1175000
				396000	1175000
				198000	1175000
			>;

 

new datasheet

(See attached i.mx6ull_datasheet_new.png)

 https://www.nxp.com/docs/en/data-sheet/IMX6ULLCEC.pdf

history

(See attached history.png)

 

It seems that VDD_SOC_CAP is for L1/L2 caches voltage.

(See attached vdd_soc_cap.png)

 

In my understanding, read/write from ROM/RAM will sometimes fail depending on a board.

However the circuit is not open and I am not sure what will occur.

 

What will occur if I set VDD_SOC_CAP 1.175V at 900MHz and why?

Why did you update the voltage at 900MHz?

 

Best regards,

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1 Solution
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igorpadykov
NXP Employee
NXP Employee

Hi shaot

 

>What will occur when setting i.mx6ull VDD_SOC_CAP at 900MHz 1.175V (Old datasheet value)?

 

this may lead to upredictable processor behaviour, exceptions or hanging. Datasheet was updated after

more factory testing and new datasheet parameters should be followed.

 

Best regards
igor

 

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2 Replies
924 Views
igorpadykov
NXP Employee
NXP Employee

Hi shaot

 

>What will occur when setting i.mx6ull VDD_SOC_CAP at 900MHz 1.175V (Old datasheet value)?

 

this may lead to upredictable processor behaviour, exceptions or hanging. Datasheet was updated after

more factory testing and new datasheet parameters should be followed.

 

Best regards
igor

 

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880 Views
shaot
Contributor II

Thank you! I am sorry for late reply.

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