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

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Message-ID: <20250607025506.GA16607@sol>
Date: Fri, 6 Jun 2025 19:55:06 -0700
From: Eric Biggers <ebiggers@...nel.org>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.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 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.
> 
> Hence, add the debugfs support to expose the PTM context to userspace from
> both PCIe RC and EP controllers. Controller drivers are expected to call
> pcie_ptm_create_debugfs() to create the debugfs attributes for the PTM
> context and call pcie_ptm_destroy_debugfs() to destroy them. The drivers
> should also populate the relevant callbacks in the 'struct pcie_ptm_ops'
> structure based on the controller implementation.
> 
> Below PTM context are exposed through debugfs:
> 
> PCIe RC
> =======
> 
> 1. PTM Local clock
> 2. PTM T2 timestamp
> 3. PTM T3 timestamp
> 4. PTM Context valid
> 
> PCIe EP
> =======
> 
> 1. PTM Local clock
> 2. PTM T1 timestamp
> 3. PTM T4 timestamp
> 4. PTM Master clock
> 5. PTM Context update
> 
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> ---
>  Documentation/ABI/testing/debugfs-pcie-ptm |  70 +++++++
>  MAINTAINERS                                |   1 +
>  drivers/pci/pcie/ptm.c                     | 300 +++++++++++++++++++++++++++++
>  include/linux/pci.h                        |  45 +++++
>  4 files changed, 416 insertions(+)

There's a build error on mainline from this commit:

    drivers/pci/pcie/ptm.c:498:25: error: redefinition of 'pcie_ptm_create_debugfs'
      498 | struct pci_ptm_debugfs *pcie_ptm_create_debugfs(struct device *dev, void *pdata,
          |                         ^
    ./include/linux/pci.h:1915:2: note: previous definition is here
     1915 | *pcie_ptm_create_debugfs(struct device *dev, void *pdata,
          |  ^
    drivers/pci/pcie/ptm.c:546:6: error: redefinition of 'pcie_ptm_destroy_debugfs'
      546 | void pcie_ptm_destroy_debugfs(struct pci_ptm_debugfs *ptm_debugfs)
          |      ^
    ./include/linux/pci.h:1918:1: note: previous definition is here
     1918 | pcie_ptm_destroy_debugfs(struct pci_ptm_debugfs *ptm_debugfs) { }
          | ^

This is with CONFIG_DEBUG_FS=n && CONFIG_PCIE_PTM=y.

- Eric