linux-kernel - [PATCH 1/2] PCI: ASPM: Allow OS to configure ASPM where BIOS is incapable of

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Message-ID: <20240530085227.91168-1-kai.heng.feng@canonical.com>
Date: Thu, 30 May 2024 16:52:26 +0800
From: Kai-Heng Feng <kai.heng.feng@...onical.com>
To: bhelgaas@...gle.com
Cc: linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	nirmal.patel@...ux.intel.com,
	jonathan.derrick@...ux.dev,
	ilpo.jarvinen@...ux.intel.com,
	david.e.box@...ux.intel.com,
	Kai-Heng Feng <kai.heng.feng@...onical.com>
Subject: [PATCH 1/2] PCI: ASPM: Allow OS to configure ASPM where BIOS is incapable of

Since commit f492edb40b54 ("PCI: vmd: Add quirk to configure PCIe ASPM
and LTR"), ASPM is configured for NVMe devices enabled in VMD domain.

However, that doesn't cover the case when FADT has ACPI_FADT_NO_ASPM
set.

So add a new attribute to bypass aspm_disabled so OS can configure ASPM.

Fixes: f492edb40b54 ("PCI: vmd: Add quirk to configure PCIe ASPM and LTR")
Link: https://lore.kernel.org/linux-pm/218aa81f-9c6-5929-578d-8dc15f83dd48@panix.com/
Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
---
 drivers/pci/pcie/aspm.c | 8 ++++++--
 include/linux/pci.h     | 1 +
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index cee2365e54b8..e719605857b1 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -1416,8 +1416,12 @@ static int __pci_enable_link_state(struct pci_dev *pdev, int state, bool locked)
 	 * the _OSC method), we can't honor that request.
 	 */
 	if (aspm_disabled) {
-		pci_warn(pdev, "can't override BIOS ASPM; OS doesn't have ASPM control\n");
-		return -EPERM;
+		if (aspm_support_enabled && pdev->aspm_os_control)
+			pci_info(pdev, "BIOS can't program ASPM, let OS control it\n");
+		else {
+			pci_warn(pdev, "can't override BIOS ASPM; OS doesn't have ASPM control\n");
+			return -EPERM;
+		}
 	}
 
 	if (!locked)
diff --git a/include/linux/pci.h b/include/linux/pci.h
index fb004fd4e889..58cbd4bea320 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -467,6 +467,7 @@ struct pci_dev {
 	unsigned int	no_command_memory:1;	/* No PCI_COMMAND_MEMORY */
 	unsigned int	rom_bar_overlap:1;	/* ROM BAR disable broken */
 	unsigned int	rom_attr_enabled:1;	/* Display of ROM attribute enabled? */
+	unsigned int	aspm_os_control:1;	/* Display of ROM attribute enabled? */
 	pci_dev_flags_t dev_flags;
 	atomic_t	enable_cnt;	/* pci_enable_device has been called */
 
-- 
2.43.0