USB Type-C Power Delivery issues with i.MX 8M Mini EVK

[maxipenna]

Hello, I'm experiencing some serious issues with following configuration:

- imx8mm-evk
- Cypress CY4500 EZ-PD
- Apple Hub A2119
- Raspberry Pi USBC power supply 5V/3A or Dell Laptop USBC power supply (5V-1A 20V-6.5A)

What I'm trying to do is provide supply through USBC hub to the evk board on USB2 primary supply port J302

The problem I see is that the board never boots into kernel and remains in u-boot in loop forever. It seems to me that PTN5110NHQZ or its u-boot driver is not working properly since is not responding to GET_SINK_CAP pd message from the hub with real values but only with GOODCRC. Other messages before perform fine so it seems some software support is already present in u-boot see image below:

what I see on cmdline is the following

U-Boot SPL 2020.04-5.10.9-1.0.0+gad7b74b415 (Mar 05 2021 - 07:05:56 +0000)
Can't find PMIC:PCA9450
DDRINFO: start DRAM init
DDRINFO: DRAM rate 3000MTS
DDRINFO:ddrphy calibration done
DDRINFO: ddrmix config done
Normal Boot
Trying to boot from MMC1
NOTICE:  BL31: v2.4(release):lf-5.10.y-1.0.0-0-gba76d337e
NOTICE:  BL31: Built : 08:27:48, Mar  1 2021


U-Boot 2020.04-5.10.9-1.0.0+gad7b74b415 (Mar 05 2021 - 07:05:56 +0000)

CPU:   i.MX8MMQ rev1.0 1800 MHz (running at 1200 MHz)
CPU:   Commercial temperature grade (0C to 95C) at 36C
Reset cause: POR
Model: NXP i.MX8MM EVK board
DRAM:  2 GiB

Software image is
yocto core-image-minimal builded as following

repo init -u https://source.codeaurora.org/external/imx/imx-manifest -b imx-linux-gatesgarth -m imx-5.10.9-1.0.0.xml
repo sync

MACHINE=imx8mmevk DISTRO=fsl-imx-xwayland source ./imx-setup-release.sh -b bld-xwayland

bitbake core-image-minimal

 
Regards,

[maxipenna · Accepted solution]

So the problem is that Apple hub is failing in detecting the current capabilities of the Raspberry Pi PSU on the hub own supply port. So that what's happening:

apple hub: Source_caps PDO Fixed 5V Max 100mA
evk: Request PDO 1 (5V) operating current 100mA and 1800mA Max with Cap Mismatch bit = 1 (means negotiation failure)
apple hub: accept & ps_rdy
apple hub: sink_caps ?
evk: answer crc okay but never respond with own sink caps

Explanation: I think tcpm driver inside u-boot on evk is going in a particular state that is marking the negotiation as invalid. The Apple hub is
not capable of sourcing the required current and the driver goes in a cycle where is answering only with crc okay messages. During the whole negotiation the evk never exceed 500mA current as required by PD specification.

Pending issues: I don't know if entering such a loop is good/bad neither if is specification compliant. Any clue?