linux-kernel - Re: [PATCH v4] PCI: Relabel JHL6540 on Lenovo X1 Carbon 7,8

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Message-ID: <20240729080441.GG1532424@black.fi.intel.com>
Date: Mon, 29 Jul 2024 11:04:41 +0300
From: Mika Westerberg <mika.westerberg@...ux.intel.com>
To: Lukas Wunner <lukas@...ner.de>
Cc: Esther Shimanovich <eshimanovich@...omium.org>,
	Mario Limonciello <mario.limonciello@....com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, Rajat Jain <rajatja@...gle.com>
Subject: Re: [PATCH v4] PCI: Relabel JHL6540 on Lenovo X1 Carbon 7,8

On Sun, Jul 28, 2024 at 05:41:09PM +0200, Lukas Wunner wrote:
> On Wed, Jun 26, 2024 at 11:59:45AM +0300, Mika Westerberg wrote:
> > On Wed, Jun 26, 2024 at 10:50:22AM +0200, Lukas Wunner wrote:
> > > On Mon, Jun 24, 2024 at 11:58:46AM -0400, Esther Shimanovich wrote:
> > > > On Wed, May 15, 2024 at 4:45???PM Lukas Wunner <lukas@...ner.de> wrote:
> > > > > Could you add this to the command line:
> > > > >   thunderbolt.dyndbg ignore_loglevel log_buf_len=10M
> > > > >
> > > > > and this to your kernel config:
> > > > >   CONFIG_DYNAMIC_DEBUG=y
> > > > >
> > > > > You should see "... is associated with ..." messages in dmesg.
> > > > 
> > > > I tried Lukas's patches again, after enabling the Thunderbolt driver
> > > > in the config and also verbose messages, so that I can see
> > > > "thunderbolt:" messages, but it still never reaches the
> > > > tb_pci_notifier_call function. I don't see "associated with" in any of
> > > > the logs. The config on the image I am testing does not have the
> > > > thunderbolt driver enabled by default, so this patch wouldn't help my
> > > > use case even if I did manage to get it to work.
> > > 
> > > Mika, what do you make of this?  Are the ChromeBooks in question
> > > using ICM-based tunneling instead of native tunneling?  I thought
> > > this is all native nowadays and ICM is only used on older (pre-USB4)
> > > products.
> > 
> > I think these are not Chromebooks. They are "regular" PCs with
> > Thunderbolt 3 host controller which is ICM as you suggest.
> > 
> > There is still Maple Ridge and Tiger Lake (non-Chrome) that are ICM
> > (firmware based connection manager) that are USB4 but everything after
> > that is software based connection manager.
> 
> Even with ICM, the DROM of the root switch seems to be retrieved:
> 
>   icm_start()
>     tb_switch_add()
>       tb_drom_read()
> 
> Assuming the DROM contains proper PCIe Upstream and Downstream Adapter
> Entries, all the data needed to at least associate the PCIe Adapters
> on the root switch should be there.  So I'm surprised Esther is not
> seeing *any* messages.
> 
> Do the DROMs on ICM root switches generally lack PCIe Upstream and
> Downstream Adapter Entries?
> What am I missing?

My guess is that they are not populated for ICM host router DROM
entries. These are pretty much Apple stuff and USB4 dropped them
completely in favour of the router operations.