linux-kernel - [PATCH V2 2/2] PCI: vmd: Use pci_host_set_default_pcie_link

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Message-ID: <20250822031159.4005529-2-david.e.box@linux.intel.com>
Date: Thu, 21 Aug 2025 20:11:58 -0700
From: "David E. Box" <david.e.box@...ux.intel.com>
To: rafael@...nel.org,
	bhelgaas@...gle.com,
	vicamo.yang@...onical.com,
	kenny@...ix.com,
	ilpo.jarvinen@...ux.intel.com,
	nirmal.patel@...ux.intel.com,
	mani@...nel.org
Cc: "David E. Box" <david.e.box@...ux.intel.com>,
	linux-pm@...r.kernel.org,
	linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH V2 2/2] PCI: vmd: Use pci_host_set_default_pcie_link_state() to set ASPM defaults

Now that pci_host_set_default_pcie_link_state() exists, set the VMD child
domain with PCIE_LINK_STATE_ALL at bridge creation so core ASPM uses those
defaults during ASPM and CLKPM capability init.

Also remove the unneeded pci_set_power_state_locked(pdev, PCI_D0) and
pci_enable_link_state_locked() calls now that the links are configured
during enumeration.

This aligns VMD behavior with platform expectations without per-controller
ASPM tweaks at runtime.

Signed-off-by: David E. Box <david.e.box@...ux.intel.com>
---
Changes in V2:

  -- Separated VMD changes into new patch.
  -- Changed comment for VMD_FEAT_BIOS_PM_QUIRK to remove ASPM
  -- Removed pci_set_power_state() and pci_enable_link_state_locked()
     calls in vmd_pm_enable_quirk()
  -- Use pci_host_set_default_pcie_link_state()

 drivers/pci/controller/vmd.c | 22 ++++++++--------------
 1 file changed, 8 insertions(+), 14 deletions(-)

diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
index b679c7f28f51..b99e01a57ddb 100644
--- a/drivers/pci/controller/vmd.c
+++ b/drivers/pci/controller/vmd.c
@@ -71,10 +71,9 @@ enum vmd_features {
 	VMD_FEAT_CAN_BYPASS_MSI_REMAP		= (1 << 4),
 
 	/*
-	 * Enable ASPM on the PCIE root ports and set the default LTR of the
-	 * storage devices on platforms where these values are not configured by
-	 * BIOS. This is needed for laptops, which require these settings for
-	 * proper power management of the SoC.
+	 * Program default LTR values for storage devices on platforms where
+	 * firmware did not. Required on many laptops for proper SoC power
+	 * management.
 	 */
 	VMD_FEAT_BIOS_PM_QUIRK		= (1 << 5),
 };
@@ -733,7 +732,7 @@ static void vmd_copy_host_bridge_flags(struct pci_host_bridge *root_bridge,
 }
 
 /*
- * Enable ASPM and LTR settings on devices that aren't configured by BIOS.
+ * Enable LTR settings on devices that aren't configured by BIOS.
  */
 static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
 {
@@ -747,7 +746,7 @@ static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
 
 	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_LTR);
 	if (!pos)
-		goto out_state_change;
+		return 0;
 
 	/*
 	 * Skip if the max snoop LTR is non-zero, indicating BIOS has set it
@@ -755,7 +754,7 @@ static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
 	 */
 	pci_read_config_dword(pdev, pos + PCI_LTR_MAX_SNOOP_LAT, &ltr_reg);
 	if (!!(ltr_reg & (PCI_LTR_VALUE_MASK | PCI_LTR_SCALE_MASK)))
-		goto out_state_change;
+		return 0;
 
 	/*
 	 * Set the default values to the maximum required by the platform to
@@ -767,13 +766,6 @@ static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
 	pci_write_config_dword(pdev, pos + PCI_LTR_MAX_SNOOP_LAT, ltr_reg);
 	pci_info(pdev, "VMD: Default LTR value set by driver\n");
 
-out_state_change:
-	/*
-	 * Ensure devices are in D0 before enabling PCI-PM L1 PM Substates, per
-	 * PCIe r6.0, sec 5.5.4.
-	 */
-	pci_set_power_state_locked(pdev, PCI_D0);
-	pci_enable_link_state_locked(pdev, PCIE_LINK_STATE_ALL);
 	return 0;
 }
 
@@ -921,6 +913,8 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
 	WARN(sysfs_create_link(&vmd->dev->dev.kobj, &vmd->bus->dev.kobj,
 			       "domain"), "Can't create symlink to domain\n");
 
+	pci_host_set_default_pcie_link_state(to_pci_host_bridge(vmd->bus->bridge),
+					     PCIE_LINK_STATE_ALL);
 	vmd_acpi_begin();
 
 	pci_scan_child_bus(vmd->bus);
-- 
2.43.0