linux-kernel - Re: [RESEND v13 01/25] CXL/PCI: Move CXL DVSEC definitions into uapi/linux/pci

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Message-ID: <20251104175030.00002268@huawei.com>
Date: Tue, 4 Nov 2025 17:50:30 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Terry Bowman <terry.bowman@....com>
CC: <dave@...olabs.net>, <dave.jiang@...el.com>, <alison.schofield@...el.com>,
	<dan.j.williams@...el.com>, <bhelgaas@...gle.com>, <shiju.jose@...wei.com>,
	<ming.li@...omail.com>, <Smita.KoralahalliChannabasappa@....com>,
	<rrichter@....com>, <dan.carpenter@...aro.org>,
	<PradeepVineshReddy.Kodamati@....com>, <lukas@...ner.de>,
	<Benjamin.Cheatham@....com>, <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	<linux-cxl@...r.kernel.org>, <alucerop@....com>, <ira.weiny@...el.com>,
	<linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>
Subject: Re: [RESEND v13 01/25] CXL/PCI: Move CXL DVSEC definitions into
 uapi/linux/pci_regs.h

On Tue, 4 Nov 2025 11:02:41 -0600
Terry Bowman <terry.bowman@....com> wrote:

> The CXL DVSECs are currently defined in cxl/core/cxlpci.h. These are not
> accessible to other subsystems. Move these to uapi/linux/pci_regs.h.
> 
> Change DVSEC name formatting to follow the existing PCI format in
> pci_regs.h. The current format uses CXL_DVSEC_XYZ and the CXL defines must
> be changed to be PCI_DVSEC_CXL_XYZ to match existing pci_regs.h. Leave
> PCI_DVSEC_CXL_PORT* defines as-is because they are already defined and may
> be in use by userspace application(s).
> 
> Update existing usage to match the name change.
> 
> Update the inline documentation to refer to latest CXL spec version.
> 
> Signed-off-by: Terry Bowman <terry.bowman@....com>
> Reviewed-by: Dave Jiang <dave.jiang@...el.com>
> 
Hi Terry,

A few minor things inline.

I'll assume you'll resolve those for next version and as they are
really minor
Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.com>


> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index b14dd064006c..53a49bb32514 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -5002,7 +5002,9 @@ static bool cxl_sbr_masked(struct pci_dev *dev)
>  	if (!dvsec)
>  		return false;
>  
> -	rc = pci_read_config_word(dev, dvsec + PCI_DVSEC_CXL_PORT_CTL, &reg);
> +	rc = pci_read_config_word(dev,
> +				  dvsec + PCI_DVSEC_CXL_PORT_CTL,
> +				  &reg);
Looks like left over from before where that define got longer?
Shouldn't still be here given the two lines are (I think?) identical other
than some premature line wrapping.
>  	if (rc || PCI_POSSIBLE_ERROR(reg))
>  		return false;
>  
> diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> index 07e06aafec50..279b92f01d08 100644
> --- a/include/uapi/linux/pci_regs.h
> +++ b/include/uapi/linux/pci_regs.h
> @@ -1244,9 +1244,64 @@
>  /* Deprecated old name, replaced with PCI_DOE_DATA_OBJECT_DISC_RSP_3_TYPE */
>  #define PCI_DOE_DATA_OBJECT_DISC_RSP_3_PROTOCOL		PCI_DOE_DATA_OBJECT_DISC_RSP_3_TYPE
>  
> -/* Compute Express Link (CXL r3.1, sec 8.1.5) */
> -#define PCI_DVSEC_CXL_PORT				3
> -#define PCI_DVSEC_CXL_PORT_CTL				0x0c
> -#define PCI_DVSEC_CXL_PORT_CTL_UNMASK_SBR		0x00000001
> +/* Compute Express Link (CXL r3.2, sec 8.1)
Follow local comment style.
/*
 * Compute Express Link (CXL r3.2, sec 8.1)
 *...

> + *
> + * Note that CXL DVSEC id 3 and 7 to be ignored when the CXL link state
> + * is "disconnected" (CXL r3.2, sec 9.12.3). Re-enumerate these
> + * registers on downstream link-up events.
> + */


> +/* CXL 3.2 8.1.8: PCIe DVSEC for Flex Bus Port */
> +#define PCI_DVSEC_CXL_FLEXBUS_PORT				7
> +#define  PCI_DVSEC_CXL_FLEXBUS_STATUS_OFFSET			0xE

I wonder if you should keep the _PORT in the naming for consistency.
These are also new defines rather than moves / renames.  I wonder if it
makes sense to bury them in this patch. Instead bring them in where they
are used?  That will also make it more obvious why only a fairly random
looking subset of this structure is used.


> +#define   PCI_DVSEC_CXL_FLEXBUS_STATUS_CACHE_MASK		_BITUL(0)
> +#define   PCI_DVSEC_CXL_FLEXBUS_STATUS_MEM_MASK			_BITUL(2)
> +
> +/* CXL 3.2 8.1.9: Register Locator DVSEC */
> +#define PCI_DVSEC_CXL_REG_LOCATOR				8
> +#define  PCI_DVSEC_CXL_REG_LOCATOR_BLOCK1_OFFSET		0xC
> +#define   PCI_DVSEC_CXL_REG_LOCATOR_BIR_MASK			__GENMASK(2, 0)
> +#define   PCI_DVSEC_CXL_REG_LOCATOR_BLOCK_ID_MASK		__GENMASK(15, 8)
> +#define   PCI_DVSEC_CXL_REG_LOCATOR_BLOCK_OFF_LOW_MASK		__GENMASK(31, 16)
>  
>  #endif /* LINUX_PCI_REGS_H */