[PATCH v20 net-next 1/9] octeontx2-af: enforce single RVU AF probe

[Ratheesh Kannoth <rkannoth@marvell.com>]

On Octeon series SoCs, the AF is an integrated device within the SoC, and
hardware resources such as NPC, NIX and related blocks are global and
coordinated by the AF driver.  Physical and virtual functions request those
resources via AF mailbox messages, so two AF driver instances cannot both
own that global state; firmware exposes only one AF PCI function at boot
and any further octeontx2-af PCI probe returns -EBUSY so software matches
the single-AF model.

Signed-off-by: Ratheesh Kannoth <rkannoth@marvell.com>
---
 drivers/net/ethernet/marvell/octeontx2/af/rvu.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/marvell/octeontx2/af/rvu.c b/drivers/net/ethernet/marvell/octeontx2/af/rvu.c
index 3cf131508ecf..12db4c7a11f8 100644
--- a/drivers/net/ethernet/marvell/octeontx2/af/rvu.c
+++ b/drivers/net/ethernet/marvell/octeontx2/af/rvu.c
@@ -3542,19 +3542,29 @@ static void rvu_update_module_params(struct rvu *rvu)
 		kpu_profile ? kpu_profile : default_pfl_name, KPU_NAME_LEN);
 }
 
+static atomic_t device_bound = ATOMIC_INIT(0);
+
 static int rvu_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 {
 	struct device *dev = &pdev->dev;
 	struct rvu *rvu;
 	int    err;
 
+	if (atomic_cmpxchg(&device_bound, 0, 1) != 0) {
+		dev_warn(dev, "Only one af device is supported.\n");
+		return -EBUSY;
+	}
+
 	rvu = devm_kzalloc(dev, sizeof(*rvu), GFP_KERNEL);
-	if (!rvu)
+	if (!rvu) {
+		atomic_set(&device_bound, 0);
 		return -ENOMEM;
+	}
 
 	rvu->hw = devm_kzalloc(dev, sizeof(struct rvu_hwinfo), GFP_KERNEL);
 	if (!rvu->hw) {
 		devm_kfree(dev, rvu);
+		atomic_set(&device_bound, 0);
 		return -ENOMEM;
 	}
 
@@ -3687,6 +3697,7 @@ static int rvu_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	pci_set_drvdata(pdev, NULL);
 	devm_kfree(&pdev->dev, rvu->hw);
 	devm_kfree(dev, rvu);
+	atomic_set(&device_bound, 0);
 	return err;
 }
 
@@ -3716,6 +3727,7 @@ static void rvu_remove(struct pci_dev *pdev)
 		cn20k_free_mbox_memory(rvu);
 	kfree(rvu->ng_rvu);
 	devm_kfree(&pdev->dev, rvu);
+	atomic_set(&device_bound, 0);
 }
 
 static void rvu_shutdown(struct pci_dev *pdev)
-- 
2.43.0