linux-kernel - Re: [PATCH v4 1/4] PCI: Add debugfs support for exposing PTM context

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Message-ID: <fehrphcqvg5nyusktj7qdxnvve2pt3rj7r7sz6p6r5qenpfq4x@r6a6fqmx5zqg>
Date: Sat, 10 May 2025 11:50:58 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>, 
	Krzysztof Wilczyński <kw@...ux.com>, Rob Herring <robh@...nel.org>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Jingoo Han <jingoohan1@...il.com>, linux-pci@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v4 1/4] PCI: Add debugfs support for exposing PTM context

On Mon, May 05, 2025 at 01:37:14PM -0500, Bjorn Helgaas wrote:
> On Mon, May 05, 2025 at 07:54:39PM +0530, Manivannan Sadhasivam wrote:
> > Precision Time Management (PTM) mechanism defined in PCIe spec r6.0,
> > sec 6.21 allows precise coordination of timing information across multiple
> > components in a PCIe hierarchy with independent local time clocks.
> > 
> > PCI core already supports enabling PTM in the root port and endpoint
> > devices through PTM Extended Capability registers. But the PTM context
> > supported by the PTM capable components such as Root Complex (RC) and
> > Endpoint (EP) controllers were not exposed as of now.
> 
> IIUC, the PCIe spec defines the PTM link protocol in terms of these
> timestamps, but it does not provide any visibility of them to
> software, so any visibility is device-specific.  I think it's worth
> mentioning something to this effect.
> 

Added this info while applying the series, thanks!

- Mani

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