linux-kernel - [PATCH v2 2/4] PCI/ASPM: Add pcie_aspm_remove_cap() to override advertised link states

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Message-ID: <20251110222929.2140564-3-helgaas@kernel.org>
Date: Mon, 10 Nov 2025 16:22:26 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: linux-pci@...r.kernel.org
Cc: Christian Zigotzky <chzigotzky@...osoft.de>,
	Manivannan Sadhasivam <mani@...nel.org>,
	mad skateman <madskateman@...il.com>,
	"R . T . Dickinson" <rtd2@...a.co.nz>,
	Darren Stevens <darren@...vens-zone.net>,
	John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
	Lukas Wunner <lukas@...ner.de>,
	luigi burdo <intermediadc@...mail.com>,
	Al <al@...azap.net>,
	Roland <rol7and@....com>,
	Hongxing Zhu <hongxing.zhu@....com>,
	hypexed@...oo.com.au,
	linuxppc-dev@...ts.ozlabs.org,
	debian-powerpc@...ts.debian.org,
	linux-kernel@...r.kernel.org,
	Bjorn Helgaas <bhelgaas@...gle.com>
Subject: [PATCH v2 2/4] PCI/ASPM: Add pcie_aspm_remove_cap() to override advertised link states

From: Bjorn Helgaas <bhelgaas@...gle.com>

Add pcie_aspm_remove_cap().  A quirk can use this to prevent use of ASPM
L0s or L1 link states, even if the device advertised support for them.

Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
---
 drivers/pci/pci.h       |  2 ++
 drivers/pci/pcie/aspm.c | 13 +++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 4492b809094b..36f8c0985430 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -958,6 +958,7 @@ void pci_save_aspm_l1ss_state(struct pci_dev *dev);
 void pci_restore_aspm_l1ss_state(struct pci_dev *dev);
 
 #ifdef CONFIG_PCIEASPM
+void pcie_aspm_remove_cap(struct pci_dev *pdev, u32 lnkcap);
 void pcie_aspm_init_link_state(struct pci_dev *pdev);
 void pcie_aspm_exit_link_state(struct pci_dev *pdev);
 void pcie_aspm_pm_state_change(struct pci_dev *pdev, bool locked);
@@ -965,6 +966,7 @@ void pcie_aspm_powersave_config_link(struct pci_dev *pdev);
 void pci_configure_ltr(struct pci_dev *pdev);
 void pci_bridge_reconfigure_ltr(struct pci_dev *pdev);
 #else
+static inline void pcie_aspm_remove_cap(struct pci_dev *pdev, u32 lnkcap) { }
 static inline void pcie_aspm_init_link_state(struct pci_dev *pdev) { }
 static inline void pcie_aspm_exit_link_state(struct pci_dev *pdev) { }
 static inline void pcie_aspm_pm_state_change(struct pci_dev *pdev, bool locked) { }
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 15d50c089070..bc3cb8bc7018 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -1542,6 +1542,19 @@ int pci_enable_link_state_locked(struct pci_dev *pdev, int state)
 }
 EXPORT_SYMBOL(pci_enable_link_state_locked);
 
+void pcie_aspm_remove_cap(struct pci_dev *pdev, u32 lnkcap)
+{
+	if (lnkcap & PCI_EXP_LNKCAP_ASPM_L0S)
+		pdev->aspm_l0s_support = 0;
+	if (lnkcap & PCI_EXP_LNKCAP_ASPM_L1)
+		pdev->aspm_l1_support = 0;
+
+	pci_info(pdev, "ASPM:%s%s removed from Link Capabilities to avoid device defect\n",
+		 lnkcap & PCI_EXP_LNKCAP_ASPM_L0S ? " L0s" : "",
+		 lnkcap & PCI_EXP_LNKCAP_ASPM_L1 ? " L1" : "");
+
+}
+
 static int pcie_aspm_set_policy(const char *val,
 				const struct kernel_param *kp)
 {
-- 
2.43.0