Linux-libre 4.8.2-gnupck-4.8.2-gnu

7 files changed, 256 insertions, 91 deletions

diff --git a/drivers/hwtracing/coresight/coresight-etm3x.c b/drivers/hwtracing/coresight/coresight-etm3x.c
index d83ab8267..2de4cad9c 100644
--- a/drivers/hwtracing/coresight/coresight-etm3x.c
+++ b/drivers/hwtracing/coresight/coresight-etm3x.c
@@ -51,6 +51,8 @@ module_param_named(boot_enable, boot_enable, int, S_IRUGO);
 static int etm_count;
 static struct etm_drvdata *etmdrvdata[NR_CPUS];
 
+static enum cpuhp_state hp_online;
+
 /*
  * Memory mapped writes to clear os lock are not supported on some processors
  * and OS lock must be unlocked before any memory mapped access on such
@@ -481,8 +483,7 @@ static int etm_enable_sysfs(struct coresight_device *csdev)
 
 	/*
 	 * Configure the ETM only if the CPU is online.  If it isn't online
-	 * hw configuration will take place when 'CPU_STARTING' is received
-	 * in @etm_cpu_callback.
+	 * hw configuration will take place on the local CPU during bring up.
 	 */
 	if (cpu_online(drvdata->cpu)) {
 		ret = smp_call_function_single(drvdata->cpu,
@@ -641,47 +642,44 @@ static const struct coresight_ops etm_cs_ops = {
 	.source_ops	= &etm_source_ops,
 };
 
-static int etm_cpu_callback(struct notifier_block *nfb, unsigned long action,
-			    void *hcpu)
+static int etm_online_cpu(unsigned int cpu)
 {
-	unsigned int cpu = (unsigned long)hcpu;
-
 	if (!etmdrvdata[cpu])
-		goto out;
+		return 0;
 
-	switch (action & (~CPU_TASKS_FROZEN)) {
-	case CPU_STARTING:
-		spin_lock(&etmdrvdata[cpu]->spinlock);
-		if (!etmdrvdata[cpu]->os_unlock) {
-			etm_os_unlock(etmdrvdata[cpu]);
-			etmdrvdata[cpu]->os_unlock = true;
-		}
-
-		if (local_read(&etmdrvdata[cpu]->mode))
-			etm_enable_hw(etmdrvdata[cpu]);
-		spin_unlock(&etmdrvdata[cpu]->spinlock);
-		break;
+	if (etmdrvdata[cpu]->boot_enable && !etmdrvdata[cpu]->sticky_enable)
+		coresight_enable(etmdrvdata[cpu]->csdev);
+	return 0;
+}
 
-	case CPU_ONLINE:
-		if (etmdrvdata[cpu]->boot_enable &&
-		    !etmdrvdata[cpu]->sticky_enable)
-			coresight_enable(etmdrvdata[cpu]->csdev);
-		break;
+static int etm_starting_cpu(unsigned int cpu)
+{
+	if (!etmdrvdata[cpu])
+		return 0;
 
-	case CPU_DYING:
-		spin_lock(&etmdrvdata[cpu]->spinlock);
-		if (local_read(&etmdrvdata[cpu]->mode))
-			etm_disable_hw(etmdrvdata[cpu]);
-		spin_unlock(&etmdrvdata[cpu]->spinlock);
-		break;
+	spin_lock(&etmdrvdata[cpu]->spinlock);
+	if (!etmdrvdata[cpu]->os_unlock) {
+		etm_os_unlock(etmdrvdata[cpu]);
+		etmdrvdata[cpu]->os_unlock = true;
 	}
-out:
-	return NOTIFY_OK;
+
+	if (local_read(&etmdrvdata[cpu]->mode))
+		etm_enable_hw(etmdrvdata[cpu]);
+	spin_unlock(&etmdrvdata[cpu]->spinlock);
+	return 0;
 }
 
-static struct notifier_block etm_cpu_notifier = {
-	.notifier_call = etm_cpu_callback,
-};
+static int etm_dying_cpu(unsigned int cpu)
+{
+	if (!etmdrvdata[cpu])
+		return 0;
+
+	spin_lock(&etmdrvdata[cpu]->spinlock);
+	if (local_read(&etmdrvdata[cpu]->mode))
+		etm_disable_hw(etmdrvdata[cpu]);
+	spin_unlock(&etmdrvdata[cpu]->spinlock);
+	return 0;
+}
 
 static bool etm_arch_supported(u8 arch)
 {
@@ -806,9 +804,17 @@ static int etm_probe(struct amba_device *adev, const struct amba_id *id)
 				     etm_init_arch_data,  drvdata, 1))
 		dev_err(dev, "ETM arch init failed\n");
 
-	if (!etm_count++)
-		register_hotcpu_notifier(&etm_cpu_notifier);
-
+	if (!etm_count++) {
+		cpuhp_setup_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING,
+					  "AP_ARM_CORESIGHT_STARTING",
+					  etm_starting_cpu, etm_dying_cpu);
+		ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+						"AP_ARM_CORESIGHT_ONLINE",
+						etm_online_cpu, NULL);
+		if (ret < 0)
+			goto err_arch_supported;
+		hp_online = ret;
+	}
 	put_online_cpus();
 
 	if (etm_arch_supported(drvdata->arch) == false) {
@@ -839,7 +845,6 @@ static int etm_probe(struct amba_device *adev, const struct amba_id *id)
 
 	pm_runtime_put(&adev->dev);
 	dev_info(dev, "%s initialized\n", (char *)id->data);
-
 	if (boot_enable) {
 		coresight_enable(drvdata->csdev);
 		drvdata->boot_enable = true;
@@ -848,8 +853,11 @@ static int etm_probe(struct amba_device *adev, const struct amba_id *id)
 	return 0;
 
 err_arch_supported:
-	if (--etm_count == 0)
-		unregister_hotcpu_notifier(&etm_cpu_notifier);
+	if (--etm_count == 0) {
+		cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING);
+		if (hp_online)
+			cpuhp_remove_state_nocalls(hp_online);
+	}
 	return ret;
 }
 
diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
index 462f0dc15..1a5e0d14c 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x.c
@@ -48,6 +48,8 @@ static int etm4_count;
 static struct etmv4_drvdata *etmdrvdata[NR_CPUS];
 static void etm4_set_default(struct etmv4_config *config);
 
+static enum cpuhp_state hp_online;
+
 static void etm4_os_unlock(struct etmv4_drvdata *drvdata)
 {
 	/* Writing any value to ETMOSLAR unlocks the trace registers */
@@ -673,47 +675,44 @@ void etm4_config_trace_mode(struct etmv4_config *config)
 	config->addr_acc[ETM_DEFAULT_ADDR_COMP + 1] = addr_acc;
 }
 
-static int etm4_cpu_callback(struct notifier_block *nfb, unsigned long action,
-			    void *hcpu)
+static int etm4_online_cpu(unsigned int cpu)
 {
-	unsigned int cpu = (unsigned long)hcpu;
-
 	if (!etmdrvdata[cpu])
-		goto out;
-
-	switch (action & (~CPU_TASKS_FROZEN)) {
-	case CPU_STARTING:
-		spin_lock(&etmdrvdata[cpu]->spinlock);
-		if (!etmdrvdata[cpu]->os_unlock) {
-			etm4_os_unlock(etmdrvdata[cpu]);
-			etmdrvdata[cpu]->os_unlock = true;
-		}
-
-		if (local_read(&etmdrvdata[cpu]->mode))
-			etm4_enable_hw(etmdrvdata[cpu]);
-		spin_unlock(&etmdrvdata[cpu]->spinlock);
-		break;
+		return 0;
 
-	case CPU_ONLINE:
-		if (etmdrvdata[cpu]->boot_enable &&
-			!etmdrvdata[cpu]->sticky_enable)
-			coresight_enable(etmdrvdata[cpu]->csdev);
-		break;
+	if (etmdrvdata[cpu]->boot_enable && !etmdrvdata[cpu]->sticky_enable)
+		coresight_enable(etmdrvdata[cpu]->csdev);
+	return 0;
+}
 
-	case CPU_DYING:
-		spin_lock(&etmdrvdata[cpu]->spinlock);
-		if (local_read(&etmdrvdata[cpu]->mode))
-			etm4_disable_hw(etmdrvdata[cpu]);
-		spin_unlock(&etmdrvdata[cpu]->spinlock);
-		break;
+static int etm4_starting_cpu(unsigned int cpu)
+{
+	if (!etmdrvdata[cpu])
+		return 0;
+
+	spin_lock(&etmdrvdata[cpu]->spinlock);
+	if (!etmdrvdata[cpu]->os_unlock) {
+		etm4_os_unlock(etmdrvdata[cpu]);
+		etmdrvdata[cpu]->os_unlock = true;
 	}
-out:
-	return NOTIFY_OK;
+
+	if (local_read(&etmdrvdata[cpu]->mode))
+		etm4_enable_hw(etmdrvdata[cpu]);
+	spin_unlock(&etmdrvdata[cpu]->spinlock);
+	return 0;
 }
 
-static struct notifier_block etm4_cpu_notifier = {
-	.notifier_call = etm4_cpu_callback,
-};
+static int etm4_dying_cpu(unsigned int cpu)
+{
+	if (!etmdrvdata[cpu])
+		return 0;
+
+	spin_lock(&etmdrvdata[cpu]->spinlock);
+	if (local_read(&etmdrvdata[cpu]->mode))
+		etm4_disable_hw(etmdrvdata[cpu]);
+	spin_unlock(&etmdrvdata[cpu]->spinlock);
+	return 0;
+}
 
 static void etm4_init_trace_id(struct etmv4_drvdata *drvdata)
 {
@@ -767,8 +766,17 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
 				etm4_init_arch_data,  drvdata, 1))
 		dev_err(dev, "ETM arch init failed\n");
 
-	if (!etm4_count++)
-		register_hotcpu_notifier(&etm4_cpu_notifier);
+	if (!etm4_count++) {
+		cpuhp_setup_state_nocalls(CPUHP_AP_ARM_CORESIGHT4_STARTING,
+					  "AP_ARM_CORESIGHT4_STARTING",
+					  etm4_starting_cpu, etm4_dying_cpu);
+		ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+						"AP_ARM_CORESIGHT4_ONLINE",
+						etm4_online_cpu, NULL);
+		if (ret < 0)
+			goto err_arch_supported;
+		hp_online = ret;
+	}
 
 	put_online_cpus();
 
@@ -809,8 +817,11 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
 	return 0;
 
 err_arch_supported:
-	if (--etm4_count == 0)
-		unregister_hotcpu_notifier(&etm4_cpu_notifier);
+	if (--etm4_count == 0) {
+		cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT4_STARTING);
+		if (hp_online)
+			cpuhp_remove_state_nocalls(hp_online);
+	}
 	return ret;
 }
 
diff --git a/drivers/hwtracing/intel_th/core.c b/drivers/hwtracing/intel_th/core.c
index 1be543e8e..6f0a51a2c 100644
--- a/drivers/hwtracing/intel_th/core.c
+++ b/drivers/hwtracing/intel_th/core.c
@@ -23,6 +23,7 @@
 #include <linux/debugfs.h>
 #include <linux/idr.h>
 #include <linux/pci.h>
+#include <linux/pm_runtime.h>
 #include <linux/dma-mapping.h>
 
 #include "intel_th.h"
@@ -67,23 +68,33 @@ static int intel_th_probe(struct device *dev)
 
 	hubdrv = to_intel_th_driver(hub->dev.driver);
 
+	pm_runtime_set_active(dev);
+	pm_runtime_no_callbacks(dev);
+	pm_runtime_enable(dev);
+
 	ret = thdrv->probe(to_intel_th_device(dev));
 	if (ret)
-		return ret;
+		goto out_pm;
 
 	if (thdrv->attr_group) {
 		ret = sysfs_create_group(&thdev->dev.kobj, thdrv->attr_group);
-		if (ret) {
-			thdrv->remove(thdev);
-
-			return ret;
-		}
+		if (ret)
+			goto out;
 	}
 
 	if (thdev->type == INTEL_TH_OUTPUT &&
 	    !intel_th_output_assigned(thdev))
+		/* does not talk to hardware */
 		ret = hubdrv->assign(hub, thdev);
 
+out:
+	if (ret)
+		thdrv->remove(thdev);
+
+out_pm:
+	if (ret)
+		pm_runtime_disable(dev);
+
 	return ret;
 }
 
@@ -103,6 +114,8 @@ static int intel_th_remove(struct device *dev)
 	if (thdrv->attr_group)
 		sysfs_remove_group(&thdev->dev.kobj, thdrv->attr_group);
 
+	pm_runtime_get_sync(dev);
+
 	thdrv->remove(thdev);
 
 	if (intel_th_output_assigned(thdev)) {
@@ -110,9 +123,14 @@ static int intel_th_remove(struct device *dev)
 			to_intel_th_driver(dev->parent->driver);
 
 		if (hub->dev.driver)
+			/* does not talk to hardware */
 			hubdrv->unassign(hub, thdev);
 	}
 
+	pm_runtime_disable(dev);
+	pm_runtime_set_active(dev);
+	pm_runtime_enable(dev);
+
 	return 0;
 }
 
@@ -185,6 +203,7 @@ static int intel_th_output_activate(struct intel_th_device *thdev)
 {
 	struct intel_th_driver *thdrv =
 		to_intel_th_driver_or_null(thdev->dev.driver);
+	int ret = 0;
 
 	if (!thdrv)
 		return -ENODEV;
@@ -192,12 +211,17 @@ static int intel_th_output_activate(struct intel_th_device *thdev)
 	if (!try_module_get(thdrv->driver.owner))
 		return -ENODEV;
 
+	pm_runtime_get_sync(&thdev->dev);
+
 	if (thdrv->activate)
-		return thdrv->activate(thdev);
+		ret = thdrv->activate(thdev);
+	else
+		intel_th_trace_enable(thdev);
 
-	intel_th_trace_enable(thdev);
+	if (ret)
+		pm_runtime_put(&thdev->dev);
 
-	return 0;
+	return ret;
 }
 
 static void intel_th_output_deactivate(struct intel_th_device *thdev)
@@ -213,6 +237,7 @@ static void intel_th_output_deactivate(struct intel_th_device *thdev)
 	else
 		intel_th_trace_disable(thdev);
 
+	pm_runtime_put(&thdev->dev);
 	module_put(thdrv->driver.owner);
 }
 
@@ -465,6 +490,38 @@ static struct intel_th_subdevice {
 	},
 };
 
+#ifdef CONFIG_MODULES
+static void __intel_th_request_hub_module(struct work_struct *work)
+{
+	struct intel_th *th = container_of(work, struct intel_th,
+					   request_module_work);
+
+	request_module("intel_th_%s", th->hub->name);
+}
+
+static int intel_th_request_hub_module(struct intel_th *th)
+{
+	INIT_WORK(&th->request_module_work, __intel_th_request_hub_module);
+	schedule_work(&th->request_module_work);
+
+	return 0;
+}
+
+static void intel_th_request_hub_module_flush(struct intel_th *th)
+{
+	flush_work(&th->request_module_work);
+}
+#else
+static inline int intel_th_request_hub_module(struct intel_th *th)
+{
+	return -EINVAL;
+}
+
+static inline void intel_th_request_hub_module_flush(struct intel_th *th)
+{
+}
+#endif /* CONFIG_MODULES */
+
 static int intel_th_populate(struct intel_th *th, struct resource *devres,
 			     unsigned int ndevres, int irq)
 {
@@ -535,7 +592,7 @@ static int intel_th_populate(struct intel_th *th, struct resource *devres,
 		/* need switch driver to be loaded to enumerate the rest */
 		if (subdev->type == INTEL_TH_SWITCH && !req) {
 			th->hub = thdev;
-			err = request_module("intel_th_%s", subdev->name);
+			err = intel_th_request_hub_module(th);
 			if (!err)
 				req++;
 		}
@@ -628,6 +685,10 @@ intel_th_alloc(struct device *dev, struct resource *devres,
 
 	dev_set_drvdata(dev, th);
 
+	pm_runtime_no_callbacks(dev);
+	pm_runtime_put(dev);
+	pm_runtime_allow(dev);
+
 	err = intel_th_populate(th, devres, ndevres, irq);
 	if (err)
 		goto err_chrdev;
@@ -635,6 +696,8 @@ intel_th_alloc(struct device *dev, struct resource *devres,
 	return th;
 
 err_chrdev:
+	pm_runtime_forbid(dev);
+
 	__unregister_chrdev(th->major, 0, TH_POSSIBLE_OUTPUTS,
 			    "intel_th/output");
 
@@ -652,12 +715,16 @@ void intel_th_free(struct intel_th *th)
 {
 	int i;
 
+	intel_th_request_hub_module_flush(th);
 	for (i = 0; i < TH_SUBDEVICE_MAX; i++)
 		if (th->thdev[i] != th->hub)
 			intel_th_device_remove(th->thdev[i]);
 
 	intel_th_device_remove(th->hub);
 
+	pm_runtime_get_sync(th->dev);
+	pm_runtime_forbid(th->dev);
+
 	__unregister_chrdev(th->major, 0, TH_POSSIBLE_OUTPUTS,
 			    "intel_th/output");
 
@@ -682,6 +749,7 @@ int intel_th_trace_enable(struct intel_th_device *thdev)
 	if (WARN_ON_ONCE(thdev->type != INTEL_TH_OUTPUT))
 		return -EINVAL;
 
+	pm_runtime_get_sync(&thdev->dev);
 	hubdrv->enable(hub, &thdev->output);
 
 	return 0;
@@ -702,6 +770,7 @@ int intel_th_trace_disable(struct intel_th_device *thdev)
 		return -EINVAL;
 
 	hubdrv->disable(hub, &thdev->output);
+	pm_runtime_put(&thdev->dev);
 
 	return 0;
 }
diff --git a/drivers/hwtracing/intel_th/gth.c b/drivers/hwtracing/intel_th/gth.c
index 9beea0b54..33e09369a 100644
--- a/drivers/hwtracing/intel_th/gth.c
+++ b/drivers/hwtracing/intel_th/gth.c
@@ -22,6 +22,7 @@
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/bitmap.h>
+#include <linux/pm_runtime.h>
 
 #include "intel_th.h"
 #include "gth.h"
@@ -190,6 +191,11 @@ static ssize_t master_attr_store(struct device *dev,
 	if (old_port >= 0) {
 		gth->master[ma->master] = -1;
 		clear_bit(ma->master, gth->output[old_port].master);
+
+		/*
+		 * if the port is active, program this setting,
+		 * implies that runtime PM is on
+		 */
 		if (gth->output[old_port].output->active)
 			gth_master_set(gth, ma->master, -1);
 	}
@@ -204,7 +210,7 @@ static ssize_t master_attr_store(struct device *dev,
 
 		set_bit(ma->master, gth->output[port].master);
 
-		/* if the port is active, program this setting */
+		/* if the port is active, program this setting, see above */
 		if (gth->output[port].output->active)
 			gth_master_set(gth, ma->master, port);
 	}
@@ -326,11 +332,15 @@ static ssize_t output_attr_show(struct device *dev,
 	struct gth_device *gth = oa->gth;
 	size_t count;
 
+	pm_runtime_get_sync(dev);
+
 	spin_lock(&gth->gth_lock);
 	count = snprintf(buf, PAGE_SIZE, "%x\n",
 			 gth_output_parm_get(gth, oa->port, oa->parm));
 	spin_unlock(&gth->gth_lock);
 
+	pm_runtime_put(dev);
+
 	return count;
 }
 
@@ -346,10 +356,14 @@ static ssize_t output_attr_store(struct device *dev,
 	if (kstrtouint(buf, 16, &config) < 0)
 		return -EINVAL;
 
+	pm_runtime_get_sync(dev);
+
 	spin_lock(&gth->gth_lock);
 	gth_output_parm_set(gth, oa->port, oa->parm, config);
 	spin_unlock(&gth->gth_lock);
 
+	pm_runtime_put(dev);
+
 	return count;
 }
 
@@ -451,7 +465,7 @@ static int intel_th_output_attributes(struct gth_device *gth)
 }
 
 /**
- * intel_th_gth_disable() - enable tracing to an output device
+ * intel_th_gth_disable() - disable tracing to an output device
  * @thdev:	GTH device
  * @output:	output device's descriptor
  *
diff --git a/drivers/hwtracing/intel_th/intel_th.h b/drivers/hwtracing/intel_th/intel_th.h
index 0df22e306..4c195786b 100644
--- a/drivers/hwtracing/intel_th/intel_th.h
+++ b/drivers/hwtracing/intel_th/intel_th.h
@@ -114,6 +114,9 @@ intel_th_output_assigned(struct intel_th_device *thdev)
  * @unassign:	deassociate an output type device from an output port
  * @enable:	enable tracing for a given output device
  * @disable:	disable tracing for a given output device
+ * @irq:	interrupt callback
+ * @activate:	enable tracing on the output's side
+ * @deactivate:	disable tracing on the output's side
  * @fops:	file operations for device nodes
  * @attr_group:	attributes provided by the driver
  *
@@ -205,6 +208,9 @@ struct intel_th {
 
 	int			id;
 	int			major;
+#ifdef CONFIG_MODULES
+	struct work_struct	request_module_work;
+#endif /* CONFIG_MODULES */
 #ifdef CONFIG_INTEL_TH_DEBUG
 	struct dentry		*dbg;
 #endif
diff --git a/drivers/hwtracing/intel_th/pci.c b/drivers/hwtracing/intel_th/pci.c
index 5e25c7eb3..0bba38423 100644
--- a/drivers/hwtracing/intel_th/pci.c
+++ b/drivers/hwtracing/intel_th/pci.c
@@ -80,6 +80,11 @@ static const struct pci_device_id intel_th_pci_id_table[] = {
 		PCI_DEVICE(PCI_VENDOR_ID_INTEL, 0x1a8e),
 		.driver_data = (kernel_ulong_t)0,
 	},
+	{
+		/* Kaby Lake PCH-H */
+		PCI_DEVICE(PCI_VENDOR_ID_INTEL, 0xa2a6),
+		.driver_data = (kernel_ulong_t)0,
+	},
 	{ 0 },
 };
 
diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
index ff31108b0..51f81d64c 100644
--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -15,6 +15,7 @@
  * as defined in MIPI STPv2 specification.
  */
 
+#include <linux/pm_runtime.h>
 #include <linux/uaccess.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -482,14 +483,40 @@ static ssize_t stm_char_write(struct file *file, const char __user *buf,
 		return -EFAULT;
 	}
 
+	pm_runtime_get_sync(&stm->dev);
+
 	count = stm_write(stm->data, stmf->output.master, stmf->output.channel,
 			  kbuf, count);
 
+	pm_runtime_mark_last_busy(&stm->dev);
+	pm_runtime_put_autosuspend(&stm->dev);
 	kfree(kbuf);
 
 	return count;
 }
 
+static void stm_mmap_open(struct vm_area_struct *vma)
+{
+	struct stm_file *stmf = vma->vm_file->private_data;
+	struct stm_device *stm = stmf->stm;
+
+	pm_runtime_get(&stm->dev);
+}
+
+static void stm_mmap_close(struct vm_area_struct *vma)
+{
+	struct stm_file *stmf = vma->vm_file->private_data;
+	struct stm_device *stm = stmf->stm;
+
+	pm_runtime_mark_last_busy(&stm->dev);
+	pm_runtime_put_autosuspend(&stm->dev);
+}
+
+static const struct vm_operations_struct stm_mmap_vmops = {
+	.open	= stm_mmap_open,
+	.close	= stm_mmap_close,
+};
+
 static int stm_char_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	struct stm_file *stmf = file->private_data;
@@ -514,8 +541,11 @@ static int stm_char_mmap(struct file *file, struct vm_area_struct *vma)
 	if (!phys)
 		return -EINVAL;
 
+	pm_runtime_get_sync(&stm->dev);
+
 	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 	vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
+	vma->vm_ops = &stm_mmap_vmops;
 	vm_iomap_memory(vma, phys, size);
 
 	return 0;
@@ -701,6 +731,17 @@ int stm_register_device(struct device *parent, struct stm_data *stm_data,
 	if (err)
 		goto err_device;
 
+	/*
+	 * Use delayed autosuspend to avoid bouncing back and forth
+	 * on recurring character device writes, with the initial
+	 * delay time of 2 seconds.
+	 */
+	pm_runtime_no_callbacks(&stm->dev);
+	pm_runtime_use_autosuspend(&stm->dev);
+	pm_runtime_set_autosuspend_delay(&stm->dev, 2000);
+	pm_runtime_set_suspended(&stm->dev);
+	pm_runtime_enable(&stm->dev);
+
 	return 0;
 
 err_device:
@@ -724,6 +765,9 @@ void stm_unregister_device(struct stm_data *stm_data)
 	struct stm_source_device *src, *iter;
 	int i, ret;
 
+	pm_runtime_dont_use_autosuspend(&stm->dev);
+	pm_runtime_disable(&stm->dev);
+
 	mutex_lock(&stm->link_mutex);
 	list_for_each_entry_safe(src, iter, &stm->link_list, link_entry) {
 		ret = __stm_source_link_drop(src, stm);
@@ -878,6 +922,8 @@ static int __stm_source_link_drop(struct stm_source_device *src,
 
 	stm_output_free(link, &src->output);
 	list_del_init(&src->link_entry);
+	pm_runtime_mark_last_busy(&link->dev);
+	pm_runtime_put_autosuspend(&link->dev);
 	/* matches stm_find_device() from stm_source_link_store() */
 	stm_put_device(link);
 	rcu_assign_pointer(src->link, NULL);
@@ -971,8 +1017,11 @@ static ssize_t stm_source_link_store(struct device *dev,
 	if (!link)
 		return -EINVAL;
 
+	pm_runtime_get(&link->dev);
+
 	err = stm_source_link_add(src, link);
 	if (err) {
+		pm_runtime_put_autosuspend(&link->dev);
 		/* matches the stm_find_device() above */
 		stm_put_device(link);
 	}
@@ -1033,6 +1082,9 @@ int stm_source_register_device(struct device *parent,
 	if (err)
 		goto err;
 
+	pm_runtime_no_callbacks(&src->dev);
+	pm_runtime_forbid(&src->dev);
+
 	err = device_add(&src->dev);
 	if (err)
 		goto err;