Re: [PATCH v14 02/16] cxl: Share CXL port upstream PCI device lookup

[Richard Cheng <icheng@nvidia.com>]

On Thu, Oct 01, 2026 at 09:22:13AM +0800, Srirangan Madhavan wrote:
> read_cdat_data() resolves a CXL port's upstream device to its backing PCI
> device. HDM cache updates need the same mapping.
> 
> Factor the lookup into cxl_port_get_uport_pci_dev() and return a referenced
> PCI device to make caller ownership explicit.
> 
> Signed-off-by: Srirangan Madhavan <smadhavan@nvidia.com>
> Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>

Reviewed-by: Richard Cheng <icheng@nvidia.com>


> ---
>  drivers/cxl/core/core.h |  1 +
>  drivers/cxl/core/pci.c  | 19 +++++--------------
>  drivers/cxl/core/port.c | 26 ++++++++++++++++++++++++++
>  3 files changed, 32 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
> index 35eaf636adc9..983d7690c3a5 100644
> --- a/drivers/cxl/core/core.h
> +++ b/drivers/cxl/core/core.h
> @@ -157,6 +157,7 @@ long cxl_pci_get_latency(struct pci_dev *pdev);
>  int cxl_pci_get_bandwidth(struct pci_dev *pdev, struct access_coordinate *c);
>  int cxl_port_get_switch_dport_bandwidth(struct cxl_port *port,
>  					struct access_coordinate *c);
> +struct pci_dev *cxl_port_get_uport_pci_dev(struct cxl_port *port);
>  
>  static inline struct device *port_to_host(struct cxl_port *port)
>  {
> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> index 9d807c1a002c..99c8b02d42e5 100644
> --- a/drivers/cxl/core/pci.c
> +++ b/drivers/cxl/core/pci.c
> @@ -564,26 +564,13 @@ static unsigned char cdat_checksum(void *buf, size_t size)
>   */
>  void read_cdat_data(struct cxl_port *port)
>  {
> -	struct device *uport = port->uport_dev;
> +	struct pci_dev *pdev = cxl_port_get_uport_pci_dev(port);
>  	struct device *dev = &port->dev;
>  	struct pci_doe_mb *doe_mb;
> -	struct pci_dev *pdev = NULL;
> -	struct cxl_memdev *cxlmd;
>  	struct cdat_doe_rsp *buf;
>  	size_t table_length, length;
>  	int rc;
>  
> -	if (is_cxl_memdev(uport)) {
> -		struct device *host;
> -
> -		cxlmd = to_cxl_memdev(uport);
> -		host = cxlmd->dev.parent;
> -		if (dev_is_pci(host))
> -			pdev = to_pci_dev(host);
> -	} else if (dev_is_pci(uport)) {
> -		pdev = to_pci_dev(uport);
> -	}
> -
>  	if (!pdev)
>  		return;
>  
> @@ -591,6 +578,7 @@ void read_cdat_data(struct cxl_port *port)
>  				      CXL_DOE_PROTOCOL_TABLE_ACCESS);
>  	if (!doe_mb) {
>  		dev_dbg(dev, "No CDAT mailbox\n");
> +		pci_dev_put(pdev);
>  		return;
>  	}
>  
> @@ -598,6 +586,7 @@ void read_cdat_data(struct cxl_port *port)
>  
>  	if (cxl_cdat_get_length(dev, doe_mb, &length)) {
>  		dev_dbg(dev, "No CDAT length\n");
> +		pci_dev_put(pdev);
>  		return;
>  	}
>  
> @@ -625,11 +614,13 @@ void read_cdat_data(struct cxl_port *port)
>  	port->cdat.table = buf->data;
>  	port->cdat.length = length;
>  
> +	pci_dev_put(pdev);
>  	return;
>  err:
>  	/* Don't leave table data allocated on error */
>  	devm_kfree(dev, buf);
>  	dev_err(dev, "Failed to read/validate CDAT.\n");
> +	pci_dev_put(pdev);
>  }
>  EXPORT_SYMBOL_NS_GPL(read_cdat_data, "CXL");
>  
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index 625e4aa427db..5dc2815d82d8 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -34,6 +34,32 @@
>  static DEFINE_IDA(cxl_port_ida);
>  static DEFINE_XARRAY(cxl_root_buses);
>  
> +/**
> + * cxl_port_get_uport_pci_dev - get the PCI device for a port's upstream device
> + * @port: CXL port to map to a PCI device
> + *
> + * Return: A referenced PCI device, or NULL if the upstream device is not PCI.
> + * The caller must release the returned reference with pci_dev_put().
> + */
> +struct pci_dev *cxl_port_get_uport_pci_dev(struct cxl_port *port)
> +{
> +	struct device *uport = port->uport_dev;
> +	struct device *host;
> +
> +	if (is_cxl_memdev(uport)) {
> +		struct cxl_memdev *cxlmd = to_cxl_memdev(uport);
> +
> +		host = cxlmd->dev.parent;
> +	} else {
> +		host = uport;
> +	}
> +
> +	if (!host || !dev_is_pci(host))
> +		return NULL;
> +
> +	return pci_dev_get(to_pci_dev(host));
> +}
> +
>  /*
>   * The terminal device in PCI is NULL and @platform_bus
>   * for platform devices (for cxl_test)
> -- 
> 2.43.0
>