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

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Date: Mon, 18 Dec 2023 15:18:40 +0200
From: Mika Westerberg <mika.westerberg@...ux.intel.com>
To: Sanath S <sanaths2@....com>
Cc: Sanath S <Sanath.S@....com>, mario.limonciello@....com,
	andreas.noever@...il.com, michael.jamet@...el.com,
	YehezkelShB@...il.com, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [Patch v2 2/2] thunderbolt: Teardown tunnels and reset
 downstream ports created by boot firmware

On Mon, Dec 18, 2023 at 06:35:13PM +0530, Sanath S wrote:
> 
> 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 ?

Wrong adapters possibly.

> 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

Definitely should be port = 5 (that's PCIe down in your log) and
hop_index = 8 (that's the one used with PCIe).

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

Can you add some more logging and provide me the dmesg or
alternativively investigate it yourself. You can use tb_port_dbg() to
get the port numbers to the log.