linux-kernel - Re: [PATCH V2 7/8] ARM: cpuidle: Register per cpuidle device

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Date:	Thu, 19 Mar 2015 09:31:12 -0600
From:	Lina Iyer <lina.iyer@...aro.org>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:	rjw@...ysocki.net, lorenzo.pieralisi@....com,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Catalin.Marinas@....com, robherring2@...il.com, arnd@...db.de,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH V2 7/8] ARM: cpuidle: Register per cpuidle device

On Wed, Mar 18 2015 at 12:46 -0600, Daniel Lezcano wrote:
>Some architectures have some cpus which does not support idle states.
>
>Let the underlying low level code to return -ENOSYS when it is not
>possible to set an idle state.
>
>Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
>---
> drivers/cpuidle/cpuidle-arm.c | 45 +++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 43 insertions(+), 2 deletions(-)
>
>diff --git a/drivers/cpuidle/cpuidle-arm.c b/drivers/cpuidle/cpuidle-arm.c
>index 1c94b88..0682ed0 100644
>--- a/drivers/cpuidle/cpuidle-arm.c
>+++ b/drivers/cpuidle/cpuidle-arm.c
>@@ -17,11 +17,14 @@
> #include <linux/kernel.h>
> #include <linux/module.h>
> #include <linux/of.h>
>+#include <linux/slab.h>
>
> #include <asm/cpuidle.h>
>
> #include "dt_idle_states.h"
>
>+static DEFINE_PER_CPU(struct cpuidle_device, *cpuidle_arm_dev);

Is a per-cpu variable needed? There seems to be no per-cpu access, other
than at init.

>+
> /*
>  * arm_enter_idle_state - Programs CPU to enter the specified state
>  *
>@@ -94,6 +97,7 @@ static int __init arm_idle_init(void)
> {
> 	int cpu, ret;
> 	struct cpuidle_driver *drv = &arm_idle_driver;
>+	struct cpuidle_device *dev;
>
> 	/*
> 	 * Initialize idle states data, starting at index 1.
>@@ -105,18 +109,55 @@ static int __init arm_idle_init(void)
> 	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) {
> 		ret = arm_cpuidle_init(cpu);
>+
>+		/* This cpu does not support any idle states */
>+		if (ret == -ENOSYS)
>+			continue;
>+
> 		if (ret) {
> 			pr_err("CPU %d failed to init idle CPU ops\n", cpu);
>-			return ret;
>+			goto out_fail;
>+		}
>+
>+		dev = kzalloc(sizeof(*dev), GFP_KERNEL);
>+		if (!dev) {
>+			pr_err("Failed to allocate cpuidle device\n");
>+			goto out_fail;
>+		}
>+
>+		dev->cpu = cpu;
>+		per_cpu(cpuidle_arm_dev, cpu) = dev;
>+
>+		ret = cpuidle_register_device(dev);
>+		if (ret) {
>+			pr_err("Failed to register cpuidle device for CPU %d\n",
>+			       cpu);
>+			kfree(dev);
>+			goto out_fail;
> 		}
> 	}
>+out:
>+	return ret;
>
>-	return cpuidle_register(drv, NULL);
>+out_fail:
>+	for (cpu--; cpu <= 0; cpu--) {
>+		dev = per_cpu(cpuidle_arm_dev, cpu);
>+		cpuidle_unregister_device(dev);
>+		kfree(dev);
>+	}
>+	cpuidle_unregister_driver(drv);
>+	goto out;
> }
> device_initcall(arm_idle_init);
>-- 
>1.9.1
>
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