IMX8MP LVDS_CTRL register documentation

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IMX8MP LVDS_CTRL register documentation

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PaulGerber
Contributor II

Hello,

on our i.MX8MP-based custom board I want to increase the driver strength for LVDS signals. I've found this function in the PHY driver: https://source.codeaurora.org/external/imx/linux-imx/tree/drivers/phy/freescale/phy-fsl-imx8mp-lvds....

In this function the LVDS_CTRL register is written, which contains some promisingly looking fields, e.g. CC_ADJ. The value of this field is hard-coded to 0x2 in the driver. Unfortunately, I cannot find any documentation for this register fields in the reference manual. I know that there is some documentation in the IMX8QM reference manual for a similar register (Section 15.4.3.2.1.3). Can anyone provide some detail on the LVDS_CTRL register on IMX8MP?

Many thanks,

Paul.

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PaulGerber
Contributor II

Hello Zhiming,

I already have this document. But in section 13.2.3.1.41, where the LVDS_CTRL register is described, there is no explanation for the values and meanings for the multi-bit fields, e.g. CC_ADJ. I assume, the higher the value in the register (0x0 ... 0x7) the higher the output current. But it's only an assumption and I'd like to have some acknowledgment.

Searching for "CC_ADJ" or "LVDS_CTRL" throughout the document doesn't help either, because there are no helpful references. Am I missing some section of the RM?

Thank you,

Paul.

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Zhiming_Liu
NXP TechSupport
NXP TechSupport

LVDS_CTRL is in MEDIA BLK_CTL registers map

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PaulGerber
Contributor II

I know that LVDS_CTRL is in MEDIA BLK_CTL. What I don't know is what different values in the CC_ADJ field (bits 13-11) in the LVDS_CTRL register mean. For example, in the IMX8QM reference manual you can see in section 15.4.3.2.1.3.3, page 5270, that a value of 100b in the CA field of the LVDS_PHY_CTRL register means an output current of 3.51mA. I'd like to have a similar information for the i.MX8MP.

Thank you,

Paul.

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Zhiming_Liu
NXP TechSupport
NXP TechSupport

I searched all released files about i.MX8MPlus, there is no such information even in lvds spec description file.

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PaulGerber
Contributor II

Hello again,

is there any chance to get some information about the LVDS_CTRL register? Somewhere in NXP I hope this is documented.

Regards,

Paul.

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michaelwalton
Contributor II

Hi Paul - yes we are facing the same issue.

Wanting to design around some parameters related to the LVDS signals and there is a lack of proper documentation as to what the default and adjustable parameters are.

So I second your request!

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Zhiming_Liu
NXP TechSupport
NXP TechSupport

Hi @PaulGerber 

Please download this document:

Qmiller_0-1652318571759.png

Regards

Zhiming

 

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