Re: [PATCH 1/4] cxl/pci: Introduce cxl_gpf_get_dvsec()

[Dave Jiang <dave.jiang@intel.com>]

On 2/18/25 11:28 PM, Davidlohr Bueso wrote:
> Add a helper to fetch the port/device GPF dvsecs. This is
> currently only used for ports, but a later patch to export
> dirty count to users will make use of the device one.
> 
> Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
> ---
>  drivers/cxl/core/pci.c | 38 ++++++++++++++++++++++++++++----------
>  drivers/cxl/cxl.h      |  2 ++
>  2 files changed, 30 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> index a5c65f79db18..2226cca3382d 100644
> --- a/drivers/cxl/core/pci.c
> +++ b/drivers/cxl/core/pci.c
> @@ -1072,6 +1072,27 @@ int cxl_pci_get_bandwidth(struct pci_dev *pdev, struct access_coordinate *c)
>  #define GPF_TIMEOUT_BASE_MAX 2
>  #define GPF_TIMEOUT_SCALE_MAX 7 /* 10 seconds */
>  
> +int cxl_gpf_get_dvsec(struct device *dev, bool port)

Maybe consider enum instead of bool. That would make it more readable. if not, maybe rename the bool to is_port

> +{
> +	struct pci_dev *pdev;
> +	int dvsec;
> +
> +	if (!dev_is_pci(dev))
> +		return -EINVAL;

Since this function is mostly a wrapper for pci_find_dvsec_capability(), why not have it return type to be u16 and just return 0 here? That way when you check you only need to verify if it's 0 (failed). 

> +
> +	pdev = to_pci_dev(dev);
> +	if (!pdev)
> +		return -EINVAL;

No need to check here. to_pci_dev() does not return a NULL. 

> +
> +	dvsec = pci_find_dvsec_capability(pdev, PCI_VENDOR_ID_CXL,
> +			port ? CXL_DVSEC_PORT_GPF : CXL_DVSEC_DEVICE_GPF);
> +	if (!dvsec)
> +		pci_warn(pdev, "%s GPF DVSEC not present\n",

why not just dev_warn() since this is cxl code and not PCI core

> +			 port ? "Port" : "Device");
> +	return dvsec;
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_gpf_get_dvsec, "CXL");
> +
>  static int update_gpf_port_dvsec(struct pci_dev *pdev, int dvsec, int phase)
>  {
>  	u64 base, scale;
> @@ -1116,26 +1137,23 @@ int cxl_gpf_port_setup(struct device *dport_dev, struct cxl_port *port)
>  {
>  	struct pci_dev *pdev;
>  
> -	if (!dev_is_pci(dport_dev))
> -		return 0;
> -
> -	pdev = to_pci_dev(dport_dev);
> -	if (!pdev || !port)
> +	if (!port)
>  		return -EINVAL;
>  
>  	if (!port->gpf_dvsec) {
>  		int dvsec;
>  
> -		dvsec = pci_find_dvsec_capability(pdev, PCI_VENDOR_ID_CXL,
> -						  CXL_DVSEC_PORT_GPF);
> -		if (!dvsec) {
> -			pci_warn(pdev, "Port GPF DVSEC not present\n");
> +		dvsec = cxl_gpf_get_dvsec(dport_dev, true);
> +		if (dvsec <= 0)
>  			return -EINVAL;
> -		}
>  
>  		port->gpf_dvsec = dvsec;
>  	}
>  
> +	pdev = to_pci_dev(dport_dev);
> +	if (!pdev)
> +		return -EINVAL;

No need to check here. macro does not return NULL.

> +
>  	update_gpf_port_dvsec(pdev, port->gpf_dvsec, 1);
>  	update_gpf_port_dvsec(pdev, port->gpf_dvsec, 2);
>  
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 6baec4ba9141..acbbba41356d 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -901,4 +901,6 @@ bool cxl_endpoint_decoder_reset_detected(struct cxl_port *port);
>  #define __mock static
>  #endif
>  
> +int cxl_gpf_get_dvsec(struct device *dev, bool port);
> +
>  #endif /* __CXL_H__ */