linux-kernel - [PATCH V2] ARM: cpuidle: Support asymmetric idle definition

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Date:   Thu,  1 Jun 2017 13:39:48 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     rjw@...ysocki.net, lorenzo.pieralisi@....com
Cc:     sudeep.holla@....com, leo.yan@...aro.org,
        linux-pm@...r.kernel.org (open list:CPUIDLE DRIVERS),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH V2] ARM: cpuidle: Support asymmetric idle definition

Some hardware have clusters with different idle states. The current code does
not support this and fails as it expects all the idle states to be identical.

Because of this, the Mediatek mtk8173 had to create the same idle state for a
big.Little system and now the Hisilicon 960 is facing the same situation.

Solve this by simply assuming the multiple driver will be needed for all the
platforms using the ARM generic cpuidle driver which makes sense because of the
different topologies we can support with a single kernel for ARM32 or ARM64.

Every CPU has its own driver, so every single CPU can specify in the DT the
idle states.

This simple approach allows to support the future dynamIQ system, current SMP
and HMP.

It is unoptimal from a memory point of view for a system with a large number of
CPUs but nowadays there is no such system with a cpuidle driver on ARM.

Tested on:
 - 96boards: Hikey 620
 - 96boards: Hikey 960
 - 96boards: dragonboard410c
 - Mediatek 8173

Tested-by: Leo Yan <leo.yan@...aro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
---
 drivers/cpuidle/Kconfig.arm   |  1 +
 drivers/cpuidle/cpuidle-arm.c | 62 ++++++++++++++++++++++++++-----------------
 2 files changed, 39 insertions(+), 24 deletions(-)

diff --git a/drivers/cpuidle/Kconfig.arm b/drivers/cpuidle/Kconfig.arm
index 21340e0..f521448 100644
--- a/drivers/cpuidle/Kconfig.arm
+++ b/drivers/cpuidle/Kconfig.arm
@@ -4,6 +4,7 @@
 config ARM_CPUIDLE
         bool "Generic ARM/ARM64 CPU idle Driver"
         select DT_IDLE_STATES
+	select CPU_IDLE_MULTIPLE_DRIVERS
         help
           Select this to enable generic cpuidle driver for ARM.
           It provides a generic idle driver whose idle states are configured
diff --git a/drivers/cpuidle/cpuidle-arm.c b/drivers/cpuidle/cpuidle-arm.c
index f440d38..7080c38 100644
--- a/drivers/cpuidle/cpuidle-arm.c
+++ b/drivers/cpuidle/cpuidle-arm.c
@@ -18,6 +18,7 @@
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/slab.h>
+#include <linux/topology.h>
 
 #include <asm/cpuidle.h>
 
@@ -44,7 +45,7 @@ static int arm_enter_idle_state(struct cpuidle_device *dev,
 	return CPU_PM_CPU_IDLE_ENTER(arm_cpuidle_suspend, idx);
 }
 
-static struct cpuidle_driver arm_idle_driver = {
+static struct cpuidle_driver arm_idle_driver __initdata = {
 	.name = "arm_idle",
 	.owner = THIS_MODULE,
 	/*
@@ -80,30 +81,42 @@ static const struct of_device_id arm_idle_state_match[] __initconst = {
 static int __init arm_idle_init(void)
 {
 	int cpu, ret;
-	struct cpuidle_driver *drv = &arm_idle_driver;
+	struct cpuidle_driver *drv;
 	struct cpuidle_device *dev;
 
-	/*
-	 * Initialize idle states data, starting at index 1.
-	 * This driver is DT only, if no DT idle states are detected (ret == 0)
-	 * let the driver initialization fail accordingly since there is no
-	 * reason to initialize the idle driver if only wfi is supported.
-	 */
-	ret = dt_init_idle_driver(drv, arm_idle_state_match, 1);
-	if (ret <= 0)
-		return ret ? : -ENODEV;
-
-	ret = cpuidle_register_driver(drv);
-	if (ret) {
-		pr_err("Failed to register cpuidle driver\n");
-		return ret;
-	}
-
-	/*
-	 * Call arch CPU operations in order to initialize
-	 * idle states suspend back-end specific data
-	 */
 	for_each_possible_cpu(cpu) {
+
+		drv = kmemdup(&arm_idle_driver, sizeof(*drv), GFP_KERNEL);
+		if (!drv) {
+			ret = -ENOMEM;
+			goto out_fail;
+		}
+
+		drv->cpumask = (struct cpumask *)cpumask_of(cpu);
+
+		/*
+		 * Initialize idle states data, starting at index 1.  This
+		 * driver is DT only, if no DT idle states are detected (ret
+		 * == 0) let the driver initialization fail accordingly since
+		 * there is no reason to initialize the idle driver if only
+		 * wfi is supported.
+		 */
+		ret = dt_init_idle_driver(drv, arm_idle_state_match, 1);
+		if (ret <= 0) {
+			ret = ret ? : -ENODEV;
+			goto out_fail;
+		}
+
+		ret = cpuidle_register_driver(drv);
+		if (ret) {
+			pr_err("Failed to register cpuidle driver\n");
+			goto out_fail;
+		}
+
+		/*
+		 * Call arch CPU operations in order to initialize
+		 * idle states suspend back-end specific data
+		 */
 		ret = arm_cpuidle_init(cpu);
 
 		/*
@@ -141,10 +154,11 @@ static int __init arm_idle_init(void)
 		dev = per_cpu(cpuidle_devices, cpu);
 		cpuidle_unregister_device(dev);
 		kfree(dev);
+		drv = cpuidle_get_driver();
+		cpuidle_unregister_driver(drv);
+		kfree(drv);
 	}
 
-	cpuidle_unregister_driver(drv);
-
 	return ret;
 }
 device_initcall(arm_idle_init);
-- 
2.7.4