linux-kernel - [PATCH AUTOSEL 4.4 01/16] PCI/ASPM: Do not initialize link state when aspm

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Date:   Fri, 25 Oct 2019 09:58:25 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Patrick Talbert <ptalbert@...hat.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Sasha Levin <sashal@...nel.org>, linux-pci@...r.kernel.org
Subject: [PATCH AUTOSEL 4.4 01/16] PCI/ASPM: Do not initialize link state when aspm_disabled is set

From: Patrick Talbert <ptalbert@...hat.com>

[ Upstream commit 17c91487364fb33797ed84022564ee7544ac4945 ]

Now that ASPM is configured for *all* PCIe devices at boot, a problem is
seen with systems that set the FADT NO_ASPM bit.  This bit indicates that
the OS should not alter the ASPM state, but when
pcie_aspm_init_link_state() runs it only checks for !aspm_support_enabled.
This misses the ACPI_FADT_NO_ASPM case because that is setting
aspm_disabled.

The result is systems may hang at boot after 1302fcf; avoidable if they
boot with pcie_aspm=off (sets !aspm_support_enabled).

Fix this by having aspm_init_link_state() check for either
!aspm_support_enabled or acpm_disabled.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=201001
Fixes: 1302fcf0d03e ("PCI: Configure *all* devices, not just hot-added ones")
Signed-off-by: Patrick Talbert <ptalbert@...hat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/pci/pcie/aspm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index c6a012b5ba390..6cc073f1d2d15 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -560,7 +560,7 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev)
 	struct pcie_link_state *link;
 	int blacklist = !!pcie_aspm_sanity_check(pdev);

-	if (!aspm_support_enabled)
+	if (!aspm_support_enabled || aspm_disabled)
 		return;

 	if (pdev->link_state)
-- 
2.20.1