linux-kernel - [PATCH 1/1] PCI/bwctrl: Fix link speed return type

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Message-Id: <20250321163103.5145-1-ilpo.jarvinen@linux.intel.com>
Date: Fri, 21 Mar 2025 18:31:03 +0200
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/1] PCI/bwctrl: Fix link speed return type

pcie_bwctrl_select_speed() should take __fls() of the speed bit, not
return it as a raw value. Instead of directly returning 2.5GT/s speed
bit, simply assign the fallback speed (2.5GT/s) into supported_speeds
variable to share the normal return path that calls
pcie_supported_speeds2target_speed() to calculate __fls().

This code path is not very likely to execute because
pcie_get_supported_speeds() should provide valid ->supported_speeds but
a spec violating device could fail to synthetize any speed in
pcie_get_supported_speeds(). It could also happen in case the
supported_speeds intersection is empty (also a violation of the current
PCIe specs).

Fixes: de9a6c8d5dbf ("PCI/bwctrl: Add pcie_set_target_speed() to set PCIe Link Speed")
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
---
 drivers/pci/pcie/bwctrl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/pcie/bwctrl.c b/drivers/pci/pcie/bwctrl.c
index 0a5e7efbce2c..58ba8142c9a3 100644
--- a/drivers/pci/pcie/bwctrl.c
+++ b/drivers/pci/pcie/bwctrl.c
@@ -113,7 +113,7 @@ static u16 pcie_bwctrl_select_speed(struct pci_dev *port, enum pci_bus_speed spe
 		up_read(&pci_bus_sem);
 	}
 	if (!supported_speeds)
-		return PCI_EXP_LNKCAP2_SLS_2_5GB;
+		supported_speeds = PCI_EXP_LNKCAP2_SLS_2_5GB;

 	return pcie_supported_speeds2target_speed(supported_speeds & desired_speeds);
 }

base-commit: 2014c95afecee3e76ca4a56956a936e23283f05b
-- 
2.39.5