linux-kernel - [PATCH v9 1/3] PCI: vmd: Set PCI devices to D0 before enable PCI PM's L1 substates

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Message-ID: <20240924071419.15350-2-jhp@endlessos.org>
Date: Tue, 24 Sep 2024 15:14:20 +0800
From: Jian-Hong Pan <jhp@...lessos.org>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Johan Hovold <johan@...nel.org>,
	David Box <david.e.box@...ux.intel.com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	Nirmal Patel <nirmal.patel@...ux.intel.com>,
	Jonathan Derrick <jonathan.derrick@...ux.dev>,
	linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux@...lessos.org,
	Jian-Hong Pan <jhp@...lessos.org>
Subject: [PATCH v9 1/3] PCI: vmd: Set PCI devices to D0 before enable PCI PM's L1 substates

The remapped PCIe Root Port and the child device have PCI PM L1 substates
capability, but they are disabled originally.

Here is a failed example on ASUS B1400CEAE:

Capabilities: [900 v1] L1 PM Substates
	L1SubCap: PCI-PM_L1.2+ PCI-PM_L1.1- ASPM_L1.2+ ASPM_L1.1- L1_PM_Substates+
		  PortCommonModeRestoreTime=32us PortTPowerOnTime=10us
	L1SubCtl1: PCI-PM_L1.2- PCI-PM_L1.1- ASPM_L1.2+ ASPM_L1.1-
		   T_CommonMode=0us LTR1.2_Threshold=101376ns
	L1SubCtl2: T_PwrOn=50us

Power on all of the VMD remapped PCI devices to D0 before enable PCI-PM L1
PM Substates by following "PCIe r6.0, sec 5.5.4".

Link: https://bugzilla.kernel.org/show_bug.cgi?id=218394
Signed-off-by: Jian-Hong Pan <jhp@...lessos.org>
---
v2:
- Power on the VMD remapped devices with pci_set_power_state_locked()
- Prepare the PCIe LTR parameters before enable L1 Substates
- Add note into the comments of both pci_enable_link_state() and
  pci_enable_link_state_locked() for kernel-doc.
- The original patch set can be split as individual patches.

v3:
- Re-send for the missed version information.
- Split drivers/pci/pcie/aspm.c modification into following patches.
- Fix the comment for enasuring the PCI devices in D0.

v4:
- The same

v5:
- Tweak the commit title and message
- Change the goto label from out_enable_link_state to out_state_change

v6~8:
- The same

v9:
- Update L1 PM Substates information against kernel v6.11 in commit message

 drivers/pci/controller/vmd.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
index 264a180403a0..11870d1fc818 100644
--- a/drivers/pci/controller/vmd.c
+++ b/drivers/pci/controller/vmd.c
@@ -740,11 +740,9 @@ static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
 	if (!(features & VMD_FEAT_BIOS_PM_QUIRK))
 		return 0;
 
-	pci_enable_link_state_locked(pdev, PCIE_LINK_STATE_ALL);
-
 	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_LTR);
 	if (!pos)
-		return 0;
+		goto out_state_change;
 
 	/*
 	 * Skip if the max snoop LTR is non-zero, indicating BIOS has set it
@@ -752,7 +750,7 @@ 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)))
-		return 0;
+		goto out_state_change;
 
 	/*
 	 * Set the default values to the maximum required by the platform to
@@ -764,6 +762,13 @@ 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;
 }
 
-- 
2.46.1