linux-kernel - Re: [PATCH v8 01/16] PCI/CXL: Introduce PCIe helper function pcie_is

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Message-ID: <67e56a9933d43_160b72946a@iweiny-mobl.notmuch>
Date: Thu, 27 Mar 2025 10:11:21 -0500
From: Ira Weiny <ira.weiny@...el.com>
To: Terry Bowman <terry.bowman@....com>, <linux-cxl@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>,
	<nifan.cxl@...il.com>, <dave@...olabs.net>, <jonathan.cameron@...wei.com>,
	<dave.jiang@...el.com>, <alison.schofield@...el.com>,
	<vishal.l.verma@...el.com>, <dan.j.williams@...el.com>,
	<bhelgaas@...gle.com>, <mahesh@...ux.ibm.com>, <ira.weiny@...el.com>,
	<oohall@...il.com>, <Benjamin.Cheatham@....com>, <rrichter@....com>,
	<nathan.fontenot@....com>, <Smita.KoralahalliChannabasappa@....com>,
	<lukas@...ner.de>, <ming.li@...omail.com>,
	<PradeepVineshReddy.Kodamati@....com>
Subject: Re: [PATCH v8 01/16] PCI/CXL: Introduce PCIe helper function
 pcie_is_cxl()

Terry Bowman wrote:
> CXL and AER drivers need the ability to identify CXL devices.
> 
> Add set_pcie_cxl() with logic checking for CXL Flexbus DVSEC presence. The
> CXL Flexbus DVSEC presence is used because it is required for all the CXL
> PCIe devices.[1]
> 
> Add boolean 'struct pci_dev::is_cxl' with the purpose to cache the CXL
> Flexbus presence.
> 
> Add function pcie_is_cxl() to return 'struct pci_dev::is_cxl'.
> 
> [1] CXL 3.1 Spec, 8.1.1 PCIe Designated Vendor-Specific Extended
>     Capability (DVSEC) ID Assignment, Table 8-2
> 
> Signed-off-by: Terry Bowman <terry.bowman@....com>
> ---
>  drivers/pci/pci.c             |  5 +++++
>  drivers/pci/probe.c           | 10 ++++++++++
>  include/linux/pci.h           |  3 +++
>  include/uapi/linux/pci_regs.h |  8 +++++++-
>  4 files changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 869d204a70a3..a1d75f40017e 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -5032,6 +5032,11 @@ static u16 cxl_port_dvsec(struct pci_dev *dev)
>  					 PCI_DVSEC_CXL_PORT);
>  }
>  
> +inline bool pcie_is_cxl(struct pci_dev *pci_dev)
> +{
> +	return pci_dev->is_cxl;
> +}

Shouldn't this just be a static inline in include/linux/pci.h?

> +
>  static bool cxl_sbr_masked(struct pci_dev *dev)
>  {
>  	u16 dvsec, reg;

[snip]

> @@ -741,6 +742,8 @@ static inline bool pci_is_vga(struct pci_dev *pdev)
>  	return false;
>  }
>  
> +bool pcie_is_cxl(struct pci_dev *pci_dev);
> +
>  #define for_each_pci_bridge(dev, bus)				\
>  	list_for_each_entry(dev, &bus->devices, bus_list)	\
>  		if (!pci_is_bridge(dev)) {} else
> diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> index 3445c4970e4d..7ccb3b2fcc38 100644
> --- a/include/uapi/linux/pci_regs.h
> +++ b/include/uapi/linux/pci_regs.h
> @@ -1208,9 +1208,15 @@
>  #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_PROTOCOL		0x00ff0000
>  #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_NEXT_INDEX	0xff000000
>  
> -/* Compute Express Link (CXL r3.1, sec 8.1.5) */
> +/* Compute Express Link (CXL r3.1, sec 8.1)
				r3.2

> + *
> + * Note that CXL DVSEC id 3 and 7 to be ignored when the CXL link state
> + * is "disconnected" (CXL r3.1, sec 9.12.3). Re-enumerate these
                             r3.2
Same sections.  :-D

With changes:

Reviewed-by: Ira Weiny <ira.weiny@...el.com>

Ira

[snip]