ARM: cpuidle: Don't register the driver when back-end init returns -ENXIO

This change “ARM: cpuidle: Don’t register the driver when back-end init returns -ENXIO” in Linux kernel is authored by Ulf Hansson <ulf.hansson [at] linaro.org> on Thu Nov 1 13:22:38 2018 +0100.

ARM: cpuidle: Don't register the driver when back-end init returns -ENXIO

There's no point to register the cpuidle driver for the current CPU, when
the initialization of the arch specific back-end data fails by returning
-ENXIO.

Instead, let's re-order the sequence to its original flow, by first trying
to initialize the back-end part and then act accordingly on the returned
error code. Additionally, let's print the error message, no matter of what
error code that was returned.

Fixes: a0d46a3dfdc3 (ARM: cpuidle: Register per cpuidle device)
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: 4.19+ <stable@vger.kernel.org> # v4.19+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

This Linux change may have been applied to various maintained Linux releases and you can find Linux releases including commit 763f191.

There are 22 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/cpuidle/cpuidle-arm.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/drivers/cpuidle/cpuidle-arm.c b/drivers/cpuidle/cpuidle-arm.c
index 073557f..df564d7 100644
--- a/drivers/cpuidle/cpuidle-arm.c
+++ b/drivers/cpuidle/cpuidle-arm.c
@@ -103,13 +103,6 @@ static int __init arm_idle_init_cpu(int cpu)
 		goto out_kfree_drv;
 	}
 
-	ret = cpuidle_register_driver(drv);
-	if (ret) {
-		if (ret != -EBUSY)
-			pr_err("Failed to register cpuidle drivern");
-		goto out_kfree_drv;
-	}
-
 	/*
 	 * Call arch CPU operations in order to initialize
 	 * idle states suspend back-end specific data
@@ -117,15 +110,20 @@ static int __init arm_idle_init_cpu(int cpu)
 	ret = arm_cpuidle_init(cpu);
 
 	/*
-	 * Skip the cpuidle device initialization if the reported
+	 * Allow the initialization to continue for other CPUs, if the reported
 	 * failure is a HW misconfiguration/breakage (-ENXIO).
 	 */
-	if (ret == -ENXIO)
-		return 0;
-
 	if (ret) {
 		pr_err("CPU %d failed to init idle CPU opsn", cpu);
-		goto out_unregister_drv;
+		ret = ret == -ENXIO ? 0 : ret;
+		goto out_kfree_drv;
+	}
+
+	ret = cpuidle_register_driver(drv);
+	if (ret) {
+		if (ret != -EBUSY)
+			pr_err("Failed to register cpuidle drivern");
+		goto out_kfree_drv;
 	}
 
 	dev = kzalloc(sizeof(*dev), GFP_KERNEL);

The commit for this change in Linux stable tree is 763f191 (patch).

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