[PATCH] cpuidle: psci: Fix support for probe deferral by dropping the faux device

[PATCH] cpuidle: psci: Fix support for probe deferral by dropping the faux device

[Ulf Hansson]

From: Ulf Hansson <ulfh@kernel.org>

At the conversion to the faux driver/device we broke the support for probe
deferral. In hindsight, the move to the faux device seems questionable, as
it simply makes the code more complicated and for no good reason.

To fix the support for the probe deferral let's therefore restore the old
code and drop the faux device.

Fixes: af5376a77e87 ("cpuidle: psci: Transition to the faux device interface")
Fixes: 5836ebeb4a2b ("cpuidle: psci: Avoid initializing faux device if no DT idle states are present")
Fixes: 39cdf87a97fd ("cpuidle: psci: Fix uninitialized variable in dt_idle_state_present()")
Cc: stable@vger.kernel.org
Signed-off-by: Ulf Hansson <ulfh@kernel.org>
---
 drivers/cpuidle/cpuidle-psci.c | 42 +++++++++++++---------------------
 1 file changed, 16 insertions(+), 26 deletions(-)

diff --git a/drivers/cpuidle/cpuidle-psci.c b/drivers/cpuidle/cpuidle-psci.c
index dcf20ea5ef5e..b250d0dde760 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/device/faux.h>
+#include <linux/platform_device.h>
 #include <linux/psci.h>
 #include <linux/pm_domain.h>
 #include <linux/pm_runtime.h>
@@ -428,14 +428,14 @@ 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 faux_device *fdev)
+static int psci_cpuidle_probe(struct platform_device *pdev)
 {
 	int cpu, ret;
 	struct cpuidle_driver *drv;
 	struct cpuidle_device *dev;
 
 	for_each_present_cpu(cpu) {
-		ret = psci_idle_init_cpu(&fdev->dev, cpu);
+		ret = psci_idle_init_cpu(&pdev->dev, cpu);
 		if (ret)
 			goto out_fail;
 	}
@@ -455,36 +455,26 @@ static int psci_cpuidle_probe(struct faux_device *fdev)
 	return ret;
 }
 
-static struct faux_device_ops psci_cpuidle_ops = {
+static struct platform_driver psci_cpuidle_driver = {
 	.probe = psci_cpuidle_probe,
+	.driver = {
+		.name = "psci-cpuidle",
+	},
 };
 
-static bool __init dt_idle_state_present(void)
-{
-	struct device_node *cpu_node __free(device_node) =
-			of_cpu_device_node_get(cpumask_first(cpu_possible_mask));
-	if (!cpu_node)
-		return false;
-
-	struct device_node *state_node __free(device_node) =
-			of_get_cpu_state_node(cpu_node, 0);
-	if (!state_node)
-		return false;
-
-	return !!of_match_node(psci_idle_state_match, state_node);
-}
-
 static int __init psci_idle_init(void)
 {
-	struct faux_device *fdev;
+	struct platform_device *pdev;
+	int ret;
 
-	if (!dt_idle_state_present())
-		return 0;
+	ret = platform_driver_register(&psci_cpuidle_driver);
+	if (ret)
+		return ret;
 
-	fdev = faux_device_create("psci-cpuidle", NULL, &psci_cpuidle_ops);
-	if (!fdev) {
-		pr_err("Failed to create psci-cpuidle device\n");
-		return -ENODEV;
+	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;
-- 
2.43.0

Re: [PATCH] cpuidle: psci: Fix support for probe deferral by dropping the faux device

[Abel Vesa]

On 26-08-26 10:45:32, Ulf Hansson wrote:
> From: Ulf Hansson <ulfh@kernel.org>
> 
> At the conversion to the faux driver/device we broke the support for probe
> deferral. In hindsight, the move to the faux device seems questionable, as
> it simply makes the code more complicated and for no good reason.
> 
> To fix the support for the probe deferral let's therefore restore the old
> code and drop the faux device.
> 
> Fixes: af5376a77e87 ("cpuidle: psci: Transition to the faux device interface")
> Fixes: 5836ebeb4a2b ("cpuidle: psci: Avoid initializing faux device if no DT idle states are present")
> Fixes: 39cdf87a97fd ("cpuidle: psci: Fix uninitialized variable in dt_idle_state_present()")
> Cc: stable@vger.kernel.org
> Signed-off-by: Ulf Hansson <ulfh@kernel.org>

LGTM.

Reviewed-by: Abel Vesa <abel.vesa@oss.qualcomm.com>