linux-kernel - [PATCH v2 2/8] cpuidle: psci: Transition to the faux device interface

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Message-Id: <20250318-plat2faux_dev-v2-2-e6cc73f78478@arm.com>
Date: Tue, 18 Mar 2025 17:01:40 +0000
From: Sudeep Holla <sudeep.holla@....com>
To: linux-kernel@...r.kernel.org
Cc: Sudeep Holla <sudeep.holla@....com>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 Lorenzo Pieralisi <lpieralisi@...nel.org>, 
 "Rafael J. Wysocki" <rafael@...nel.org>, 
 Daniel Lezcano <daniel.lezcano@...aro.org>, linux-pm@...r.kernel.org
Subject: [PATCH v2 2/8] cpuidle: psci: Transition to the faux device
 interface

The PSCI cpuidle driver does not require the creation of a platform
device. Originally, this approach was chosen for simplicity when the
driver was first implemented.

With the introduction of the lightweight faux device interface, we now
have a more appropriate alternative. Migrate the driver to utilize the
faux bus, given that the platform device it previously created was not
a real one anyway. This will simplify the code, reducing its footprint
while maintaining functionality.

Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: linux-pm@...r.kernel.org
Signed-off-by: Sudeep Holla <sudeep.holla@....com>
---
 drivers/cpuidle/cpuidle-psci.c | 32 ++++----------------------------
 1 file changed, 4 insertions(+), 28 deletions(-)

diff --git a/drivers/cpuidle/cpuidle-psci.c b/drivers/cpuidle/cpuidle-psci.c
index 2562dc001fc1de69732ef28f383d2809262a3d96..5d4d6daed36d8540ba2ce3dc54a3180731b03d22 100644
--- a/drivers/cpuidle/cpuidle-psci.c
+++ b/drivers/cpuidle/cpuidle-psci.c
@@ -16,7 +16,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
-#include <linux/platform_device.h>
+#include <linux/device/faux.h>
 #include <linux/psci.h>
 #include <linux/pm_domain.h>
 #include <linux/pm_runtime.h>
@@ -404,14 +404,14 @@ static int psci_idle_init_cpu(struct device *dev, int cpu)
  * to register cpuidle driver then rollback to cancel all CPUs
  * registration.
  */
-static int psci_cpuidle_probe(struct platform_device *pdev)
+static int psci_cpuidle_probe(struct faux_device *fdev)
 {
 	int cpu, ret;
 	struct cpuidle_driver *drv;
 	struct cpuidle_device *dev;

 	for_each_possible_cpu(cpu) {
-		ret = psci_idle_init_cpu(&pdev->dev, cpu);
+		ret = psci_idle_init_cpu(&fdev->dev, cpu);
 		if (ret)
 			goto out_fail;
 	}
@@ -431,28 +431,4 @@ static int psci_cpuidle_probe(struct platform_device *pdev)
 	return ret;
 }

-static struct platform_driver psci_cpuidle_driver = {
-	.probe = psci_cpuidle_probe,
-	.driver = {
-		.name = "psci-cpuidle",
-	},
-};
-
-static int __init psci_idle_init(void)
-{
-	struct platform_device *pdev;
-	int ret;
-
-	ret = platform_driver_register(&psci_cpuidle_driver);
-	if (ret)
-		return ret;
-
-	pdev = platform_device_register_simple("psci-cpuidle", -1, NULL, 0);
-	if (IS_ERR(pdev)) {
-		platform_driver_unregister(&psci_cpuidle_driver);
-		return PTR_ERR(pdev);
-	}
-
-	return 0;
-}
-device_initcall(psci_idle_init);
+module_faux_driver(psci_cpuidle, psci_cpuidle_probe, NULL, true);

-- 
2.34.1