[PATCH] PCI/ASPM: Fix L1 sub-state handling in aspm_attr_store_common

From: Heiner Kallweit <hkallweit1@gmail.com>
To: Bjorn Helgaas <bhelgaas@google.com>
Cc: "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>
Subject: [PATCH] PCI/ASPM: Fix L1 sub-state handling in aspm_attr_store_common
Date: Wed, 11 Oct 2023 09:46:45 +0200	[thread overview]
Message-ID: <6ba7dd79-9cfe-4ed0-a002-d99cb842f361@gmail.com> (raw)

So far we may see an unexpected behavior regard L1 sub-states.
Following scenario:

Write 0 to "l1_aspm" to disable L1
Write 1 to "l1_1_aspm" to enable L1.1

Intention of step 1 is to implicitly disable also L1.1 and L1.2.
However after step 2 L1.2 is unexpectedly enabled.

Fix this by explicitly disabling L1 sub-states when disabling L1.

Fixes: 72ea91afbfb0 ("PCI/ASPM: Add sysfs attributes for controlling ASPM link states")
Link: https://lore.kernel.org/linux-pci/20231002151452.GA560499@bhelgaas/
Cc: stable@vger.kernel.org
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
Splitted-out part of original patch according to linked discussion.
---
 drivers/pci/pcie/aspm.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 530c3bb5708c..fc18e42f0a6e 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -1248,6 +1248,8 @@ static ssize_t aspm_attr_store_common(struct device *dev,
 			link->aspm_disable &= ~ASPM_STATE_L1;
 	} else {
 		link->aspm_disable |= state;
+		if (state & ASPM_STATE_L1)
+			link->aspm_disable |= ASPM_STATE_L1SS;
 	}
 
 	pcie_config_aspm_link(link, policy_to_aspm_state(link));
-- 
2.42.0

