Re: [PATCH 1/2] drm/xe/pf: Create a link between PF and VF devices

["Piotr Piórkowski" <piotr.piorkowski@intel.com>]

Satyanarayana K V P <satyanarayana.k.v.p@intel.com> wrote on czw [2025-lut-20 12:11:18 +0530]:
> When both PF and VF devices are enabled on the host, they
> resume simultaneously during system resume.
> 
> However, the PF must finish provisioning the VF before any
> VFs can successfully resume.
> 
> Establish a parent-child device link between the PF and VF
> devices to ensure the correct order of resumption.
> 
> Signed-off-by: Satyanarayana K V P <satyanarayana.k.v.p@intel.com>
> Cc: Michał Wajdeczko <michal.wajdeczko@intel.com>
> Cc: Michał Winiarski <michal.winiarski@intel.com>
> Cc: Piotr Piórkowski <piotr.piorkowski@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_pci_sriov.c | 37 +++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_pci_sriov.c b/drivers/gpu/drm/xe/xe_pci_sriov.c
> index aaceee748287..429e1c7909a1 100644
> --- a/drivers/gpu/drm/xe/xe_pci_sriov.c
> +++ b/drivers/gpu/drm/xe/xe_pci_sriov.c
> @@ -62,6 +62,41 @@ static void pf_reset_vfs(struct xe_device *xe, unsigned int num_vfs)
>  			xe_gt_sriov_pf_control_trigger_flr(gt, n);
>  }
>  
> +static void pf_link_vfs(struct xe_device *xe, int num_vfs)
> +{
> +	struct pci_dev *pdev_pf = to_pci_dev(xe->drm.dev);
> +	int domain = pci_domain_nr(pdev_pf->bus);
> +	unsigned int bus = pdev_pf->bus->number;
> +	struct device_link *link;
> +	struct pci_dev *pdev_vf;
> +	unsigned int n;
> +
> +	for (n = 1; n <= num_vfs; n++) {
> +		pdev_vf = pci_get_domain_bus_and_slot(domain, bus,
> +						      pci_iov_virtfn_devfn(pdev_pf, n - 1));
I think this function requires a call pci_dev_put when you have finished using pdev_vf
> +
> +		if (!pdev_vf) {
> +			xe_sriov_notice(xe, "Can't link PF and VF%d due to missing pci dev..\n", n);
> 
 I wonder if the log about the missing VF pci device is not a serious enough problem to deserve at least a warn 
Thanks,
Piotr
> +			continue;
> +		}
> +
> +		/*
> +		 * When both PF and VF devices are enabled on the host, during system
> +		 * resume they are resuming in parallel.
> +		 *
> +		 * But PF has to complete the provision of VF first to allow any VFs to
> +		 * successfully resume.
> +		 *
> +		 * Create a parent-child device link between PF and VF devices that will
> +		 * enforce correct resume order.
> +		 */
> +		link = device_link_add(&pdev_vf->dev, &pdev_pf->dev,
> +				       DL_FLAG_AUTOREMOVE_CONSUMER);
> +		if (!link)
> +			xe_sriov_notice(xe, "Failed linking PF and VF%u\n", n);
> +	}
> +}
> +
>  static int pf_enable_vfs(struct xe_device *xe, int num_vfs)
>  {
>  	struct pci_dev *pdev = to_pci_dev(xe->drm.dev);
> @@ -92,6 +127,8 @@ static int pf_enable_vfs(struct xe_device *xe, int num_vfs)
>  	if (err < 0)
>  		goto failed;
>  
> +	pf_link_vfs(xe, num_vfs);
> +
>  	xe_sriov_info(xe, "Enabled %u of %u VF%s\n",
>  		      num_vfs, total_vfs, str_plural(total_vfs));
>  	return num_vfs;
> -- 
> 2.35.3
> 

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