Re: [Patch v2 2/2] thunderbolt: Teardown tunnels and reset downstream ports created by boot firmware

[Sanath S <sanaths2@amd.com>]

On 12/18/2023 5:53 PM, Mika Westerberg wrote:
> On Mon, Dec 18, 2023 at 01:31:51PM +0200, Mika Westerberg wrote:
>> On Mon, Dec 18, 2023 at 04:49:13PM +0530, Sanath S wrote:
>>>> The discover part should not do anything (like write the hardware) so
>>>> perhaps it is just some timing thing (but that's weird too).
>>>>
>>>> I think we should do something like this:
>>>>
>>>> 1. Disable all enabled protocol adapters (reset them to defaults).
>>>> 2. Clear all protocol adapter paths.
>>>> 3. Issue DPR over all enabled USB4 ports.
>>>>
>>>> BTW, what you mean "didn't work"?
>>> Path activation would go fine after DPR like below:
>>>
>>> [   15.090905] thunderbolt 0000:c4:00.5: 0:5 <-> 2:9 (PCI): activating
>>> [   15.090932] thunderbolt 0000:c4:00.5: activating PCIe Down path from 0:5
>>> to 2:9
>>> [   15.091602] thunderbolt 0000:c4:00.5: activating PCIe Up path from 2:9 to
>>> 0:5
>>>
>>> But, PCIE enumeration doesn't happen (pcie link up will not happen, will not
>>> see below logs)
>>> [   15.134223] pcieport 0000:00:03.1: pciehp: Slot(0-1): Card present
>>> [   15.134243] pcieport 0000:00:03.1: pciehp: Slot(0-1): Link Up
>> Okay, what if you like reset the PCIe adapter config spaces back to the
>> defaults? Just as an experiment.
> If this turns out to be really complex then I guess it is better to do
> it like you did originally using discovery but at least it would be nice
> to see what the end result of this experiment looks like :)

Yes, I'll give a try.
As an experiment, I tried to compare the path deactivation that occurs 
at two place.
1. In tb_switch_reset where we are calling tb_path_deactivate_hop(port, i).
2. While we get a unplug event after doing DPR.

I observed both have different hop_index and port numbers.
So, are we calling tb_path_deactivate_hop with wrong hop ids ?

 From deactivate tunnel (called while unplug) :
[    3.408268] thunderbolt 0000:c4:00.5: deactivating PCIe Down path 
from 2:9 to 0:5
[    3.408282] deactivate hop port = 9 hop_index=8
[    3.408328] deactivate hop port = 2 hop_index=10

Deactivate from tb_switch_reset() :
deactivate hop port = 5 hop_index=8