gpu: nvgpu: sysfs to put gpu into idle

- Add a sysfs "force_idle" to forcibly idle the GPU
- read on this sysfs will return the current status

0 : not in idle (running)
1 : in forced idle state

"echo 1 > force_idle" will force the gpu into idle
"echo 0 > force_idle" will cause the gpu to resume

Bug 1376916
Bug 1487804

Change-Id: I48dfd52e0d14561220bc4baea0776d1bdfaa7ea5
Signed-off-by: Deepak Nibade <dnibade@nvidia.com>

drivers/gpu/nvgpu/gk20a/gk20a.h

@@ -248,6 +248,7 @@ struct gk20a {
 	bool elcg_enabled;
 	bool elpg_enabled;
 	bool aelpg_enabled;
+	bool forced_idle;
 
 #ifdef CONFIG_DEBUG_FS
 	spinlock_t debugfs_lock;

drivers/gpu/nvgpu/gk20a/gk20a_sysfs.c

@@ -22,6 +22,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/kernel.h>
 #include <linux/fb.h>
+#include <linux/gk20a.h>
 
 #include <mach/clk.h>
 
@@ -331,6 +332,55 @@ static ssize_t elpg_enable_read(struct device *device,
 
 static DEVICE_ATTR(elpg_enable, ROOTRW, elpg_enable_read, elpg_enable_store);
 
+static ssize_t force_idle_store(struct device *device,
+	struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct platform_device *ndev = to_platform_device(device);
+	struct gk20a *g = get_gk20a(ndev);
+	unsigned long val = 0;
+	int err = 0;
+
+	if (kstrtoul(buf, 10, &val) < 0)
+		return -EINVAL;
+
+	if (val) {
+		if (g->forced_idle)
+			return count; /* do nothing */
+		else {
+			err = gk20a_do_idle();
+			if (!err) {
+				g->forced_idle = 1;
+				dev_info(device, "gpu is idle : %d\n",
+					g->forced_idle);
+			}
+		}
+	} else {
+		if (!g->forced_idle)
+			return count; /* do nothing */
+		else {
+			err = gk20a_do_unidle();
+			if (!err) {
+				g->forced_idle = 0;
+				dev_info(device, "gpu is idle : %d\n",
+					g->forced_idle);
+			}
+		}
+	}
+
+	return count;
+}
+
+static ssize_t force_idle_read(struct device *device,
+	struct device_attribute *attr, char *buf)
+{
+	struct platform_device *ndev = to_platform_device(device);
+	struct gk20a *g = get_gk20a(ndev);
+
+	return sprintf(buf, "%d\n", g->forced_idle ? 1 : 0);
+}
+
+static DEVICE_ATTR(force_idle, ROOTRW, force_idle_read, force_idle_store);
+
 void gk20a_remove_sysfs(struct device *dev)
 {
 	struct gk20a *g = get_gk20a(to_platform_device(dev));
@@ -345,6 +395,7 @@ void gk20a_remove_sysfs(struct device *dev)
 	device_remove_file(dev, &dev_attr_load);
 	device_remove_file(dev, &dev_attr_railgate_delay);
 	device_remove_file(dev, &dev_attr_clockgate_delay);
+	device_remove_file(dev, &dev_attr_force_idle);
 
 	if (g->host1x_dev && (dev->parent != &g->host1x_dev->dev))
 		sysfs_remove_link(&dev->kobj, dev_name(dev));
@@ -365,6 +416,7 @@ void gk20a_create_sysfs(struct platform_device *dev)
 	error |= device_create_file(&dev->dev, &dev_attr_load);
 	error |= device_create_file(&dev->dev, &dev_attr_railgate_delay);
 	error |= device_create_file(&dev->dev, &dev_attr_clockgate_delay);
+	error |= device_create_file(&dev->dev, &dev_attr_force_idle);
 
 	if (g->host1x_dev && (dev->dev.parent != &g->host1x_dev->dev))
 		error |= sysfs_create_link(&g->host1x_dev->dev.kobj,