Re: [PATCH 4/6] ARM: OMAP4: PMU: Add runtime PM support

[Jon Hunter <jon-hunter@ti.com>]

Hi Kevin, Will,

On 05/30/2012 08:29 PM, Will Deacon wrote:
> Hi Kevin,
> 
> On Wed, May 30, 2012 at 10:50:01PM +0100, Kevin Hilman wrote:
>> Basically, I don't like the result when we have to hack around missing
>> runtime PM support for a driver, so IMO, the driver should be updated.
>>
>> IOW, it looks to me like the armpmu driver should grow runtime PM
>> support.  The current armpmu_release|reserve should probably be replaced
>> with runtime PM get/put, and the functionality in those functions would
>> be the runtime PM callbacks instead.
>>
>> Will, any objections to armpmu growing runtime PM support?
> 
> My plan for the armpmu reservation is to kill the global reservation scheme
> that we currently have and push those function pointers into the arm_pmu,
> so that fits with what you'd like.
> 
> The only concern I have is that we need the mutual exclusion even when we
> don't have support for runtime PM. If we can solve that then I'm fine with
> the approach.

To add a bit more food for thought, I had implemented a quick patch to add runtime PM support for PMU. You will notice that I have been conservative on where I have placed the pm_runtime_get/put calls, because I am not too familiar with the PMU driver to know exactly where we need to maintain the PMU context. So right now these are just around the reserve_hardware/release_hardware calls. This works on OMAP for some quick testing. However, I would need to make sure this does not break compilation without runtime PM enabled.

Let me know your thoughts.

Cheers
Jon

>From b111bcb24737e070ee1ce7ea3d1deb60a4d6f266 Mon Sep 17 00:00:00 2001
From: Jon Hunter <jon-hunter@ti.com>
Date: Thu, 31 May 2012 13:05:20 -0500
Subject: [PATCH] ARM: PMU: Add runtime PM Support

---
 arch/arm/include/asm/pmu.h   |    2 ++
 arch/arm/kernel/perf_event.c |   30 ++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/arch/arm/include/asm/pmu.h b/arch/arm/include/asm/pmu.h
index 90114fa..db9f20c 100644
--- a/arch/arm/include/asm/pmu.h
+++ b/arch/arm/include/asm/pmu.h
@@ -43,6 +43,8 @@ struct arm_pmu_platdata {
 				  irq_handler_t pmu_handler);
 	void (*enable_irq)(int irq);
 	void (*disable_irq)(int irq);
+	int (*runtime_resume)(struct device *dev);
+	int (*runtime_suspend)(struct device *dev);
 };
 
 #ifdef CONFIG_CPU_HAS_PMU
diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index 186c8cb..3b2b016 100644
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -20,6 +20,7 @@
 #include <linux/platform_device.h>
 #include <linux/spinlock.h>
 #include <linux/uaccess.h>
+#include <linux/pm_runtime.h>
 
 #include <asm/cputype.h>
 #include <asm/irq.h>
@@ -460,6 +461,8 @@ hw_perf_event_destroy(struct perf_event *event)
 		armpmu_release_hardware(armpmu);
 		mutex_unlock(pmu_reserve_mutex);
 	}
+
+	pm_runtime_put_sync(&armpmu->plat_device->dev);
 }
 
 static int
@@ -546,6 +549,8 @@ static int armpmu_event_init(struct perf_event *event)
 	if (armpmu->map_event(event) == -ENOENT)
 		return -ENOENT;
 
+	pm_runtime_get_sync(&armpmu->plat_device->dev);
+
 	event->destroy = hw_perf_event_destroy;
 
 	if (!atomic_inc_not_zero(active_events)) {
@@ -584,6 +589,26 @@ static void armpmu_disable(struct pmu *pmu)
 	armpmu->stop();
 }
 
+static int armpmu_runtime_resume(struct device *dev)
+{
+	struct arm_pmu_platdata *plat = dev_get_platdata(dev);
+
+	if (plat->runtime_resume)
+		return plat->runtime_resume(dev);
+
+	return 0;
+}
+
+static int armpmu_runtime_suspend(struct device *dev)
+{
+	struct arm_pmu_platdata *plat = dev_get_platdata(dev);
+
+	if (plat->runtime_suspend)
+		return plat->runtime_suspend(dev);
+
+	return 0;
+}
+
 static void __init armpmu_init(struct arm_pmu *armpmu)
 {
 	atomic_set(&armpmu->active_events, 0);
@@ -650,9 +675,14 @@ static int __devinit armpmu_device_probe(struct platform_device *pdev)
 	return 0;
 }
 
+static const struct dev_pm_ops armpmu_dev_pm_ops = {
+	SET_RUNTIME_PM_OPS(armpmu_runtime_suspend, armpmu_runtime_resume, NULL)
+};
+
 static struct platform_driver armpmu_driver = {
 	.driver		= {
 		.name	= "arm-pmu",
+		.pm	= &armpmu_dev_pm_ops,
 		.of_match_table = armpmu_of_device_ids,
 	},
 	.probe		= armpmu_device_probe,
-- 
1.7.9.5