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From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Linux PCI <linux-pci@vger.kernel.org>
Cc: Linux PM <linux-pm@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Bjorn Helgaas <helgaas@kernel.org>,
	Mika Westerberg <mika.westerberg@linux.intel.com>
Subject: [PATCH v3 8/9] PCI/PM: Avoid redundant current_state update
Date: Thu, 14 Apr 2022 15:18:15 +0200	[thread overview]
Message-ID: <1844408.CQOukoFCf9@kreacher> (raw)
In-Reply-To: <5838942.lOV4Wx5bFT@kreacher>

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

Notice that if pci_power_up() returns success early, without updating
the given device's PCI_PM_CTRL register, because it has verified that
the power state of the device is D0 already at that point, the
pci_update_current_state() invocation in pci_pm_default_resume_early()
is redundant.

Avoid that redundant call by making pci_power_up() return 1 when it
has updated the device's PCI_PM_CTRL register and checking its return
value in pci_pm_default_resume_early().

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---

v2 -> v3:
   * Added R-by from Mika.

---
 drivers/pci/pci-driver.c |    5 +++--
 drivers/pci/pci.c        |   10 ++++++++--
 2 files changed, 11 insertions(+), 4 deletions(-)

Index: linux-pm/drivers/pci/pci-driver.c
===================================================================
--- linux-pm.orig/drivers/pci/pci-driver.c
+++ linux-pm/drivers/pci/pci-driver.c
@@ -553,8 +553,9 @@ static void pci_pm_default_resume(struct
 
 static void pci_pm_default_resume_early(struct pci_dev *pci_dev)
 {
-	pci_power_up(pci_dev);
-	pci_update_current_state(pci_dev, PCI_D0);
+	if (pci_power_up(pci_dev))
+		pci_update_current_state(pci_dev, PCI_D0);
+
 	pci_restore_state(pci_dev);
 	pci_pme_restore(pci_dev);
 }
Index: linux-pm/drivers/pci/pci.c
===================================================================
--- linux-pm.orig/drivers/pci/pci.c
+++ linux-pm/drivers/pci/pci.c
@@ -1189,6 +1189,12 @@ static int pci_dev_wait(struct pci_dev *
 /**
  * pci_power_up - Put the given device into D0
  * @dev: PCI device to power up
+ *
+ * Use the platform firmware and the PCI_PM_CTRL register to put @dev into D0.
+ *
+ * Return 0 if invoking the platform firmware was sufficient to put @dev into D0
+ * (and so the PCI_PM_CTRL register was not updated), or 1 if it was necessary to
+ * update the PCI_PM_CTRL register, or -ENODEV if the device was not accessible.
  */
 int pci_power_up(struct pci_dev *dev)
 {
@@ -1244,7 +1250,7 @@ int pci_power_up(struct pci_dev *dev)
 		udelay(PCI_PM_D2_DELAY);
 
 	dev->current_state = PCI_D0;
-	return 0;
+	return 1;
 
 fail:
 	pci_err(dev, "Unable to change power state to D0, device inaccessible\n");
@@ -1294,7 +1300,7 @@ static int pci_set_full_power_state(stru
 	int ret;
 
 	ret = pci_power_up(dev);
-	if (ret)
+	if (ret < 0)
 		return ret;
 
 	if (!dev->pm_cap)




  parent reply	other threads:[~2022-04-14 13:24 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-09 13:03 [PATCH v1 0/7] PCI/PM: Improvements related to device transitions into D0 Rafael J. Wysocki
2022-04-09 13:05 ` [PATCH v1 1/7] PCI/PM: Resume subordinate bus in bus type callbacks Rafael J. Wysocki
2022-04-09 13:06 ` [PATCH v1 2/7] PCI/PM: Drop the runtime_d3cold PCI device flag Rafael J. Wysocki
2022-04-09 13:08 ` [PATCH v1 3/7] PCI/PM: Rearrange pci_update_current_state() Rafael J. Wysocki
2022-04-09 13:22 ` [PATCH v1 4/7] PCI/PM: Rework changing power states of PCI devices Rafael J. Wysocki
2022-04-09 13:23 ` [PATCH v1 5/7] PCI/PM: Move pci_set_low_power_state() next to its caller Rafael J. Wysocki
2022-04-09 13:26 ` [PATCH v1 6/7] PCI/PM: Clean up pci_set_low_power_state() Rafael J. Wysocki
2022-04-09 13:28 ` [PATCH v1 7/7] PCI/PM: Rearrange pci_set_power_state() Rafael J. Wysocki
2022-04-11 14:17 ` [PATCH v2 0/9] PCI/PM: Improvements related to device transitions into D0 Rafael J. Wysocki
2022-04-11 14:19   ` [PATCH v2 1/9] PCI/PM: Resume subordinate bus in bus type callbacks Rafael J. Wysocki
2022-04-11 14:20   ` [PATCH v2 2/9] PCI/PM: Drop the runtime_d3cold device flag Rafael J. Wysocki
2022-04-11 14:21   ` [PATCH v2 3/9] PCI/PM: Rearrange pci_update_current_state() Rafael J. Wysocki
2022-04-12  9:42     ` Mika Westerberg
2022-04-12 10:56       ` Rafael J. Wysocki
2022-04-11 14:25   ` [PATCH v2 4/9] PCI/PM: Rework changing power states of PCI devices Rafael J. Wysocki
2022-04-12 10:00     ` Mika Westerberg
2022-04-12 11:31       ` Rafael J. Wysocki
2022-04-12 11:38         ` Mika Westerberg
2022-04-11 14:27   ` [PATCH v2 5/9] PCI/PM: Move pci_set_low_power_state() next to its caller Rafael J. Wysocki
2022-04-11 14:28   ` [PATCH v2 6/9] PCI/PM: Clean up pci_set_low_power_state() Rafael J. Wysocki
2022-04-11 14:30   ` [PATCH v2 7/9] PCI/PM: Rearrange pci_set_power_state() Rafael J. Wysocki
2022-04-11 14:31   ` [PATCH v2 8/9] PCI/PM: Avoid redundant current_state update Rafael J. Wysocki
2022-04-11 14:33   ` [PATCH v2 9/9] PCI/PM: Replace pci_set_power_state() in pci_pm_thaw_noirq() Rafael J. Wysocki
2022-04-11 14:33   ` [PATCH v2 0/9] PCI/PM: Improvements related to device transitions into D0 Rafael J. Wysocki
2022-04-12 10:08   ` Mika Westerberg
2022-04-12 11:34     ` Rafael J. Wysocki
2022-04-14 13:00   ` [PATCH v3 " Rafael J. Wysocki
2022-04-14 13:04     ` [PATCH v3 1/9] PCI/PM: Resume subordinate bus in bus type callbacks Rafael J. Wysocki
2022-04-14 13:04     ` [PATCH v3 2/9] PCI/PM: Drop the runtime_d3cold device flag Rafael J. Wysocki
2022-04-14 13:07     ` [PATCH v3 3/9] PCI/PM: Rearrange pci_update_current_state() Rafael J. Wysocki
2022-04-14 13:11     ` [PATCH v3 4/9] PCI/PM: Rework changing power states of PCI devices Rafael J. Wysocki
2022-05-03 17:59       ` Nathan Chancellor
2022-05-04 12:59         ` Rafael J. Wysocki
2022-05-04 15:54           ` Anders Roxell
2022-05-04 16:36           ` Nathan Chancellor
2022-05-04 18:00             ` Rafael J. Wysocki
2022-05-04 19:35               ` Nathan Chancellor
2022-05-05 11:58                 ` Rafael J. Wysocki
2022-05-04 16:54         ` Bjorn Helgaas
2022-05-04 17:15           ` Rafael J. Wysocki
2022-04-14 13:14     ` [PATCH v3 5/9] PCI/PM: Move pci_set_low_power_state() next to its caller Rafael J. Wysocki
2022-04-14 13:15     ` [PATCH v3 6/9] PCI/PM: Clean up pci_set_low_power_state() Rafael J. Wysocki
2022-04-14 13:17     ` [PATCH v3 7/9] PCI/PM: Rearrange pci_set_power_state() Rafael J. Wysocki
2022-04-14 13:18     ` Rafael J. Wysocki [this message]
2022-04-14 13:19     ` [PATCH v3 9/9] PCI/PM: Replace pci_set_power_state() in pci_pm_thaw_noirq() Rafael J. Wysocki
2022-04-20 16:25     ` [PATCH v3 0/9] PCI/PM: Improvements related to device transitions into D0 Bjorn Helgaas
2022-04-20 16:28       ` Rafael J. Wysocki

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