i.MX8MQ USB3 PHY: about tuning parameters

jnagat — Thu, 19 Jun 2025 08:57:51 GMT

Hi,

I need to adjust signal waveform on USB.
The below URL is the device tree of i.MX8MQ on the GitHub, and I can find USB-related parameters.
linux-imx/Documentation/devicetree/bindings/phy/fsl,imx8mq-usb-phy.yaml at lf-6.6.y_6.6.52-2.2.0_var01 · varigit/linux-imx · GitHub

I would like to know is that how to use following seven parameters. There is short descriptions on each parameter, but I do not understand the effect on signal waveform when parameters are changed.
Could you tell me descriptions in detail to adjust USB waveform, or share any documents with me.

//-------------------------------
fsl,phy-tx-vref-tune-percent:
description:
Tunes the HS DC level relative to the nominal level
minimum: 94
maximum: 124

fsl,phy-tx-rise-tune-percent:
description:
Adjusts the rise/fall time duration of the HS waveform relative to
its nominal value
minimum: 97
maximum: 103

fsl,phy-tx-preemp-amp-tune-microamp:
description:
Adjust amount of current sourced to DPn and DMn after a J-to-K
or K-to-J transition. Default is 0 (disabled).
minimum: 0
maximum: 1800

fsl,phy-tx-vboost-level-microvolt:
description:
Adjust the boosted transmit launch pk-pk differential amplitude
minimum: 880
maximum: 1120

fsl,phy-comp-dis-tune-percent:
description:
Adjust the voltage level used to detect a disconnect event at the host
relative to the nominal value
minimum: 91
maximum: 115

fsl,phy-pcs-tx-deemph-3p5db-attenuation-db:
description:
Adjust TX de-emphasis attenuation in dB at nominal
3.5dB point as per USB specification
$ref: /schemas/types.yaml#/definitions/uint32
minimum: 0
maximum: 36

fsl,phy-pcs-tx-swing-full-percent:
description:
Scaling of the voltage defined by fsl,phy-tx-vboost-level-microvolt
minimum: 0
maximum: 100
----------------------------------//

Best regards,

jnagat

Embedded Software and Tools Clinicのトピックi.MX8MQ USB3 PHY: about tuning parameters

i.MX8MQ USB3 PHY: about tuning parameters