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

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Date: Fri, 5 Jan 2024 09:06:11 +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 Thu, Jan 04, 2024 at 10:19:20PM +0530, Sanath S wrote:
> 
> On 12/19/2023 5:56 PM, Mika Westerberg wrote:
> > On Tue, Dec 19, 2023 at 02:41:08PM +0530, Sanath S wrote:
> > > On 12/18/2023 6:48 PM, Mika Westerberg wrote:
> > > > 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 :)
> > > I feel it's better to go with discover and then reset for now (as v3).
> > > I'll keep this experiment as "to do" and will send out when I crack it down.
> I got what we were missing. It's not required to do a discover_tunnel before
> we tear down.
> 
> We were resetting the downstream port and do a "continue;"
> So, we were not cleaning up its path. Actually we have to cleanup its path
> after DPR.
> 
> After changing it, It works without any tunnel_discover() api's.

Makes sense, good finding.