linux-kernel - [PATCH v2 2/3] sis-agp: use generic power management

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Date:   Tue, 12 Jan 2021 13:39:23 +0530
From:   Vaibhav Gupta <vaibhavgupta40@...il.com>
To:     Bjorn Helgaas <helgaas@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Bjorn Helgaas <bjorn@...gaas.com>,
        Vaibhav Gupta <vaibhav.varodek@...il.com>,
        David Airlie <airlied@...ux.ie>
Cc:     Vaibhav Gupta <vaibhavgupta40@...il.com>,
        linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: [PATCH v2 2/3] sis-agp: use generic power management

Drivers should do only device-specific jobs. But in general, drivers using
legacy PCI PM framework for .suspend()/.resume() have to manage many PCI
PM-related tasks themselves which can be done by PCI Core itself. This
brings extra load on the driver and it directly calls PCI helper functions
to handle them.

Switch to the new generic framework by updating function signatures and
define a "struct dev_pm_ops" variable to bind PM callbacks. Also, remove
unnecessary calls to the PCI Helper functions along with the legacy
.suspend & .resume bindings.

After upgrading, .suspend() became an empty-body function, hence defined as
NULL.

Signed-off-by: Vaibhav Gupta <vaibhavgupta40@...il.com>
---
 drivers/char/agp/sis-agp.c | 25 ++++++-------------------
 1 file changed, 6 insertions(+), 19 deletions(-)

diff --git a/drivers/char/agp/sis-agp.c b/drivers/char/agp/sis-agp.c
index 14909fc5d767..f8a02f4bef1b 100644
--- a/drivers/char/agp/sis-agp.c
+++ b/drivers/char/agp/sis-agp.c
@@ -217,26 +217,14 @@ static void agp_sis_remove(struct pci_dev *pdev)
 	agp_put_bridge(bridge);
 }
 
-#ifdef CONFIG_PM
+#define agp_sis_suspend NULL
 
-static int agp_sis_suspend(struct pci_dev *pdev, pm_message_t state)
+static int __maybe_unused agp_sis_resume(
+	__attribute__((unused)) struct device *dev)
 {
-	pci_save_state(pdev);
-	pci_set_power_state(pdev, pci_choose_state(pdev, state));
-
-	return 0;
-}
-
-static int agp_sis_resume(struct pci_dev *pdev)
-{
-	pci_set_power_state(pdev, PCI_D0);
-	pci_restore_state(pdev);
-
 	return sis_driver.configure();
 }
 
-#endif /* CONFIG_PM */
-
 static const struct pci_device_id agp_sis_pci_table[] = {
 	{
 		.class		= (PCI_CLASS_BRIDGE_HOST << 8),
@@ -419,15 +407,14 @@ static const struct pci_device_id agp_sis_pci_table[] = {
 
 MODULE_DEVICE_TABLE(pci, agp_sis_pci_table);
 
+static SIMPLE_DEV_PM_OPS(agp_sis_pm_ops, agp_sis_suspend, agp_sis_resume);
+
 static struct pci_driver agp_sis_pci_driver = {
 	.name		= "agpgart-sis",
 	.id_table	= agp_sis_pci_table,
 	.probe		= agp_sis_probe,
 	.remove		= agp_sis_remove,
-#ifdef CONFIG_PM
-	.suspend	= agp_sis_suspend,
-	.resume		= agp_sis_resume,
-#endif
+	.driver.pm      = &agp_sis_pm_ops,
 };
 
 static int __init agp_sis_init(void)
-- 
2.30.0