Re: So, I had to revert d6d458d42e1 ("Handle DisplayPort tunnel activation asynchronously") too, to stop my resume crashes

Kenneth Crudup
2025-03-03T14:17:09Z

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Oh, and to be complete I should point out I have the following attached
commit against Linus' master, else I don't get full power savings during
s0ix sleep.

(I've been trying to get the PM people to get a version of this in for
nearly a year now.)

I don't think it's relevant here, but just-in-case ....

-Kenny

--
Kenneth R. Crudup / Sr. SW Engineer, Scott County Consulting, Orange
County CA

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From 849e27052d5a1e279cce7b6ab14e40a39c3b2b24 Mon Sep 17 00:00:00 2001
From: "Kenneth R. Crudup" <kenny@panix.com>
Date: Fri, 13 Dec 2024 15:28:42 -0800
Subject: [PATCH] PCI/ASPM: Fixup ASPM for VMD bridges

Effectively a squashed commit of:
UBUNTU: SAUCE: PCI/ASPM: Enable ASPM for links under VMD domain
UBUNTU: SAUCE: PCI/ASPM: Enable LTR for endpoints behind VMD
UBUNTU: SAUCE: vmd: fixup bridge ASPM by driver name instead
---
drivers/pci/pcie/aspm.c | 28 +++++++++++++++++++++++++++-
1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 28567d457613..a5df6230cf3c 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -768,6 +768,31 @@ static void aspm_l1ss_init(struct pcie_link_state *link)
aspm_calc_l12_info(link, parent_l1ss_cap, child_l1ss_cap);
}

+/*
+ * BIOS may not be able to access config space of devices under VMD domain, so
+ * it relies on software to enable ASPM for links under VMD.
+ */
+static bool pci_fixup_vmd_bridge_enable_aspm(struct pci_dev *pdev)
+{
+ struct pci_bus *bus = pdev->bus;
+ struct device *dev;
+ struct pci_driver *pdrv;
+
+ if (!pci_is_root_bus(bus))
+ return false;
+
+ dev = bus->bridge->parent;
+ if (dev == NULL)
+ return false;
+
+ pdrv = pci_dev_driver(to_pci_dev(dev));
+ if (pdrv == NULL || strcmp("vmd", pdrv->name))
+ return false;
+
+ pci_info(pdev, "enable ASPM for pci bridge behind vmd");
+ return true;
+}
+
static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
{
struct pci_dev *child = link->downstream, *parent = link->pdev;
@@ -846,7 +871,8 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
}

/* Save default state */
- link->aspm_default = link->aspm_enabled;
+ link->aspm_default = pci_fixup_vmd_bridge_enable_aspm(parent) ?
+ PCIE_LINK_STATE_ASPM_ALL : link->aspm_enabled;

/* Setup initial capable state. Will be updated later */
link->aspm_capable = link->aspm_support;
--
2.45.2