Problem with old Lenovo laptops and PR_SWAP

[OlEr_1999891]

Hi

We have a problem with the PD-negotiation on some old Lenovo laptops. The problem seems to be that after the dock have made a PR_SWAP and all is good the dock is sending a source-cap request to the laptop and the laptop doesn't ack this with GOODCRC. After som attempt the dock forces a HARDWARE reset.

So root problem is that of course that the laptop doesn't respond to the source-cap request at all, but it is a bit unclear why the dock sends a source-cap request at all after the power swap. There is no need for that at this point.

Maybe there is a setting in the CYPD4226 FW where that behaviour can be disabled?

Attached this PD-log. First instance of the problem is on line 94-100.

Cheers

Olof

[Pranava_YN]

Hi,

Can you please share the Firmware project you are using for the dock? I will go through it and get back to you regarding this issue.

[OlEr_1999891 · Accepted solution]

Hi Pranava!

Thanks for getting back. Will send source-code separately. 

Noticed another similar issue one the same type of laptops, this time the laptop misses to send GOODCRC on VDM-messages, more or less at the same point in the state-machine I believe. The VDMs in question originate from the HPD-events from the TV.

Cheers

Olof

[Pranava_YN]

Hi,

There was an issue with the laptops wherein it stopped responding to PD messages after PR_SWAP is issued. Switching to power role Source helped resolve this.