Subject: [Very RFC 40/46] powernv/npu: Don't drop refcount when looking up GPU pci_devs

From: Oliver O'Halloran <[email-masked]>
Date: Wed, 20 Nov 2019 12:28:53 +1100

The comment here implies that we don't need to take a ref to the pci_dev
because the ioda_pe will always have one. This implies that the current
expection is that the pci_dev for an NPU device will *never* be torn
down since the ioda_pe having a ref to the device will prevent the
release function from being called.

In other words, the desired behaviour here appears to be leaking a ref.

Nice!

Signed-off-by: Oliver O'Halloran <[email-masked]>
---
 arch/powerpc/platforms/powernv/npu-dma.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/npu-dma.c b/arch/powerpc/platforms/powernv/npu-dma.c
index 72d3749da02c..2eb6e6d45a98 100644
--- a/arch/powerpc/platforms/powernv/npu-dma.c
+++ b/arch/powerpc/platforms/powernv/npu-dma.c
@@ -28,15 +28,10 @@ static struct pci_dev *get_pci_dev(struct device_node *dn)
 			break;
 
 	/*
-	 * pci_get_domain_bus_and_slot() increased the reference count of
-	 * the PCI device, but callers don't need that actually as the PE
-	 * already holds a reference to the device. Since callers aren't
-	 * aware of the reference count change, call pci_dev_put() now to
-	 * avoid leaks.
+	 * NB: for_each_pci_dev() elevates the pci_dev refcount.
+	 * Caller is responsible for dropping the ref when it's
+	 * finished with it.
 	 */
-	if (pdev)
-		pci_dev_put(pdev);
-
 	return pdev;
 }
 
-- 
2.21.0