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

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Date: Tue, 23 Apr 2024 11:40:23 +0300
From: Mika Westerberg <mika.westerberg@...ux.intel.com>
To: Lukas Wunner <lukas@...ner.de>
Cc: Mario Limonciello <mario.limonciello@....com>,
	Esther Shimanovich <eshimanovich@...omium.org>,
	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 Tue, Apr 23, 2024 at 10:31:30AM +0200, Lukas Wunner wrote:
> On Tue, Apr 23, 2024 at 08:33:12AM +0300, Mika Westerberg wrote:
> > I think what you are looking for is that anything behind a PCIe tunnel
> > should not have this applied. IIRC the AMD GPU or some code there were
> > going to add identification of "virtual" links to the bandwidth
> > calculation functionality.
> 
> I guess I could resurrect my correlation patch:
> 
> https://lore.kernel.org/all/f53ea40a7487e145aa1a62c347cef1814072e140.1536517047.git.lukas@wunner.de/
> 
> The last time I forward-ported it was for v5.13.  I still have that code
> running on my development machine.
> 
> The problem is that it only allows lookup from tb_port to pci_dev.
> I'd have to add a pointer to struct pci_dev to allow lookups in the
> inverse direction.  Though I think we have such PCI companion devices
> for CXL as well, so such a pointer could be useful in general.
> 
> I'm knee-deep in PCI device authentication code but could probably
> dedicate a weekend to the correlation patch if there's interest?
> 
> Once we have correlation, we can expose more precise bandwidth
> for virtual PCI links in sysfs.

Sounds good to me :) There are also some additions in USB4 spec that
allows discovery of mapping between PCIe adapters and the corresponding
PCIe downstream/root port. Perhaps these can be added there too?