linux-kernel - [PATCH v1] PCI: Increase maximum PCIe physical function number to 7 for non-ARI devices

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Date: Fri, 16 Feb 2024 18:24:49 +0100
From: Bean Huo <beanhuo@...pp.de>
To: bhelgaas@...gle.com,
	schnelle@...ux.ibm.com
Cc: linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Bean Huo <beanhuo@...ron.com>
Subject: [PATCH v1] PCI: Increase maximum PCIe physical function number to 7 for non-ARI devices

From: Bean Huo <beanhuo@...ron.com>

The PCIe specification allows up to 8 Physical Functions (PFs) per endpoint
when ARI (Alternative Routing-ID Interpretation) is not supported. Previously,
our implementation erroneously limited the maximum number of PFs to 7 for
endpoints without ARI support.

This patch corrects the maximum PF count to adhere to the PCIe specification
by allowing up to 8 PFs on non-ARI endpoints. This change ensures better
compliance with the standard and improves compatibility with devices relying
on this specification.

This adjustment was verified against the PCIe spec (reference specific
sections if applicable) and tested with a range of PCIe devices not supporting
ARI to ensure no regressions in functionality.

Signed-off-by: Bean Huo <beanhuo@...ron.com>
---
 drivers/pci/probe.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index ed6b7f48736a..8c3d0f63bc13 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2630,7 +2630,8 @@ static int next_fn(struct pci_bus *bus, struct pci_dev *dev, int fn)
 	if (pci_ari_enabled(bus))
 		return next_ari_fn(bus, dev, fn);

-	if (fn >= 7)
+	/* If EP does not support ARI, the maximum number of functions should be 7 */
+	if (fn > 7)
 		return -ENODEV;
 	/* only multifunction devices may have more functions */
 	if (dev && !dev->multifunction)
-- 
2.34.1