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

[Satyanarayana K V P]

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 at intel.com>
Cc: Michał Wajdeczko <michal.wajdeczko at intel.com>
Cc: Michał Winiarski <michal.winiarski at intel.com>
Cc: Piotr Piórkowski <piotr.piorkowski at 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));
+
+		if (!pdev_vf) {
+			xe_sriov_notice(xe, "Can't link PF and VF%d due to missing pci dev..\n", n);
+			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