linux-kernel - [PATCH v2 7/9] PCI/PM: Rearrange pci_set_power

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Date:   Mon, 11 Apr 2022 16:30:00 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Linux PCI <linux-pci@...r.kernel.org>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: [PATCH v2 7/9] PCI/PM: Rearrange pci_set_power_state()

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

The part of pci_set_power_state() related to transitions into
low-power states is unnecessary convoluted, so clearly divide it
into the D3cold special case and the general case covering all of
the other states.

Also fix a potential issue with calling pci_bus_set_current_state()
to set the current state of all devices on the subordinate to D3cold
without checking if the power state of the parent bridge has really
changed to D3cold.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---

v1 -> v2: No changes.

---
 drivers/pci/pci.c |   28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

Index: linux-pm/drivers/pci/pci.c
===================================================================
--- linux-pm.orig/drivers/pci/pci.c
+++ linux-pm/drivers/pci/pci.c
@@ -1431,19 +1431,25 @@ int pci_set_power_state(struct pci_dev *
 	if (state >= PCI_D3hot && (dev->dev_flags & PCI_DEV_FLAGS_NO_D3))
 		return 0;
 
-	/*
-	 * To put device in D3cold, we put device into D3hot in native
-	 * way, then put device into D3cold with platform ops
-	 */
-	error = pci_set_low_power_state(dev, state > PCI_D3hot ?
-					PCI_D3hot : state);
+	if (state == PCI_D3cold) {
+		/*
+		 * To put the device in D3cold, put it into D3hot in the native
+		 * way, then put it into D3cold using platform ops.
+		 */
+		error = pci_set_low_power_state(dev, PCI_D3hot);
 
-	if (pci_platform_power_transition(dev, state))
-		return error;
+		if (pci_platform_power_transition(dev, PCI_D3cold))
+			return error;
 
-	/* Powering off a bridge may power off the whole hierarchy */
-	if (state == PCI_D3cold)
-		pci_bus_set_current_state(dev->subordinate, PCI_D3cold);
+		/* Powering off a bridge may power off the whole hierarchy */
+		if (dev->current_state == PCI_D3cold)
+			pci_bus_set_current_state(dev->subordinate, PCI_D3cold);
+	} else {
+		error = pci_set_low_power_state(dev, state);
+
+		if (pci_platform_power_transition(dev, state))
+			return error;
+	}
 
 	return 0;
 }