linux-kernel - [PATCH v2] PCI: Check PCIe upstream port for PME support

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Date:   Thu, 12 Aug 2021 23:39:44 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     bhelgaas@...gle.com
Cc:     Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Lukas Wunner <lukas@...ner.de>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        linux-pci@...r.kernel.org (open list:PCI SUBSYSTEM),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v2] PCI: Check PCIe upstream port for PME support

Some platforms cannot detect ethernet hotplug once its upstream port is
runtime suspended because PME isn't granted by BIOS _OSC. The issue can
be workarounded by "pcie_ports=native".

The vendor confirmed that the PME in _OSC is disabled intentionally for
system stability issues on the other OS, so we should also honor the PME
setting here.

So before marking PME support status for the device, check
PCI_EXP_RTCTL_PMEIE bit to ensure PME interrupt is either enabled by
firmware or OS.

Cc: Lukas Wunner <lukas@...ner.de>
Cc: Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=213873
Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
---
v2:
 - Instead of prevent root port from runtime suspending, skip
   initializing PME status for the downstream device.

 drivers/pci/pci.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index aacf575c15cf..4344dc302edd 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2294,6 +2294,32 @@ void pci_pme_wakeup_bus(struct pci_bus *bus)
 		pci_walk_bus(bus, pci_pme_wakeup, (void *)true);
 }
 
+#ifdef CONFIG_PCIE_PME
+static bool pci_pcie_port_pme_enabled(struct pci_dev *dev)
+{
+	struct pci_dev *bridge = pci_upstream_bridge(dev);
+	u16 val;
+	int ret;
+
+	if (!bridge)
+		return true;
+
+	if (pci_pcie_type(bridge) != PCI_EXP_TYPE_ROOT_PORT &&
+	    pci_pcie_type(bridge) != PCI_EXP_TYPE_RC_EC)
+		return true;
+
+	ret = pcie_capability_read_word(bridge, PCI_EXP_RTCTL, &val);
+	if (ret)
+		return false;
+
+	return val & PCI_EXP_RTCTL_PMEIE;
+}
+#else
+static bool pci_pcie_port_pme_enabled(struct pci_dev *dev)
+{
+	return true;
+}
+#endif
 
 /**
  * pci_pme_capable - check the capability of PCI device to generate PME#
@@ -3095,7 +3121,7 @@ void pci_pm_init(struct pci_dev *dev)
 	}
 
 	pmc &= PCI_PM_CAP_PME_MASK;
-	if (pmc) {
+	if (pmc && pci_pcie_port_pme_enabled(dev)) {
 		pci_info(dev, "PME# supported from%s%s%s%s%s\n",
 			 (pmc & PCI_PM_CAP_PME_D0) ? " D0" : "",
 			 (pmc & PCI_PM_CAP_PME_D1) ? " D1" : "",
-- 
2.32.0