[v5,3/6] thermal: Add generic power domain warming device driver.
diff mbox series

Message ID 20200320014107.26087-4-thara.gopinath@linaro.org
State Changes Requested, archived
Headers show
Series
  • Introduce Power domain based warming device driver
Related show

Commit Message

Thara Gopinath March 20, 2020, 1:41 a.m. UTC
Resources modeled as power domains in linux kernel can  be used to warm the
SoC(eg. mx power domain on sdm845).  To support this feature, introduce a
generic power domain warming device driver that can be plugged into the
thermal framework (The thermal framework itself requires further
modifiction to support a warming device in place of a cooling device.
Those extensions are not introduced in this patch series).

Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
---

v3->v4:
	- Removed late_init hook pd_warming_device_ops.
	- Use of_genpd_add_device instead of pm_genpd_add_device to attach
	  device to the generic power domain.
	- Use thermal_of_cooling_device_parent_register to register the
	  cooling device so that the device with genpd attached can be
	  made parent of the cooling device.
	- With above changes, remove reference to generic_pm_domain in
	  pd_warming_device.

v4->v5:
	- All the below changes are as per Ulf's review comments.
	- Renamed pwr_domain_warming.c and pwr_domain_warming.h to
	  pd_warming.c and pd_warming.h.
	- Renamed pwr_domain_warming_register API to 
	  of_pd_warming_register.
	- Dropped in-param pd_name to of_pd_warming_register.
	- Introduced ID allocator to uniquely identify each power domain
	  warming device.
	- Introduced pd_warming_release to handle device kfree for
	  pd_warming_device.
	- Introduced pm_genpd_remove_device in the error exit path
	  of of_pd_warming_register.

 drivers/thermal/Kconfig      |  10 +++
 drivers/thermal/Makefile     |   2 +
 drivers/thermal/pd_warming.c | 168 +++++++++++++++++++++++++++++++++++
 include/linux/pd_warming.h   |  29 ++++++
 4 files changed, 209 insertions(+)
 create mode 100644 drivers/thermal/pd_warming.c
 create mode 100644 include/linux/pd_warming.h

Comments

Ulf Hansson March 23, 2020, 3:57 p.m. UTC | #1
On Fri, 20 Mar 2020 at 02:41, Thara Gopinath <thara.gopinath@linaro.org> wrote:
>
> Resources modeled as power domains in linux kernel can  be used to warm the
> SoC(eg. mx power domain on sdm845).  To support this feature, introduce a
> generic power domain warming device driver that can be plugged into the
> thermal framework (The thermal framework itself requires further
> modifiction to support a warming device in place of a cooling device.
> Those extensions are not introduced in this patch series).
>
> Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
> ---
>
> v3->v4:
>         - Removed late_init hook pd_warming_device_ops.
>         - Use of_genpd_add_device instead of pm_genpd_add_device to attach
>           device to the generic power domain.
>         - Use thermal_of_cooling_device_parent_register to register the
>           cooling device so that the device with genpd attached can be
>           made parent of the cooling device.
>         - With above changes, remove reference to generic_pm_domain in
>           pd_warming_device.
>
> v4->v5:
>         - All the below changes are as per Ulf's review comments.
>         - Renamed pwr_domain_warming.c and pwr_domain_warming.h to
>           pd_warming.c and pd_warming.h.
>         - Renamed pwr_domain_warming_register API to
>           of_pd_warming_register.
>         - Dropped in-param pd_name to of_pd_warming_register.
>         - Introduced ID allocator to uniquely identify each power domain
>           warming device.
>         - Introduced pd_warming_release to handle device kfree for
>           pd_warming_device.
>         - Introduced pm_genpd_remove_device in the error exit path
>           of of_pd_warming_register.
>
>  drivers/thermal/Kconfig      |  10 +++
>  drivers/thermal/Makefile     |   2 +
>  drivers/thermal/pd_warming.c | 168 +++++++++++++++++++++++++++++++++++
>  include/linux/pd_warming.h   |  29 ++++++
>  4 files changed, 209 insertions(+)
>  create mode 100644 drivers/thermal/pd_warming.c
>  create mode 100644 include/linux/pd_warming.h
>
> diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
> index 4d6753f2b18f..92522d541d0e 100644
> --- a/drivers/thermal/Kconfig
> +++ b/drivers/thermal/Kconfig
> @@ -206,6 +206,16 @@ config DEVFREQ_THERMAL
>
>           If you want this support, you should say Y here.
>
> +config PWR_DOMAIN_WARMING_THERMAL
> +       bool "Power Domain based warming device"
> +       depends on PM_GENERIC_DOMAINS_OF
> +       help
> +         This implements the generic power domain based warming
> +         mechanism through increasing the performance state of
> +         a power domain.
> +
> +         If you want this support, you should say Y here.
> +
>  config THERMAL_EMULATION
>         bool "Thermal emulation mode support"
>         help
> diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
> index 8c8ed7b79915..7db87a779126 100644
> --- a/drivers/thermal/Makefile
> +++ b/drivers/thermal/Makefile
> @@ -28,6 +28,8 @@ thermal_sys-$(CONFIG_CLOCK_THERMAL)   += clock_cooling.o
>  # devfreq cooling
>  thermal_sys-$(CONFIG_DEVFREQ_THERMAL) += devfreq_cooling.o
>
> +thermal_sys-$(CONFIG_PWR_DOMAIN_WARMING_THERMAL)       += pd_warming.o
> +
>  # platform thermal drivers
>  obj-y                          += broadcom/
>  obj-$(CONFIG_THERMAL_MMIO)             += thermal_mmio.o
> diff --git a/drivers/thermal/pd_warming.c b/drivers/thermal/pd_warming.c
> new file mode 100644
> index 000000000000..c0854d2e4b92
> --- /dev/null
> +++ b/drivers/thermal/pd_warming.c
> @@ -0,0 +1,168 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2019, Linaro Ltd
> + */
> +#include <linux/err.h>
> +#include <linux/kernel.h>
> +#include <linux/init.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/module.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/slab.h>
> +#include <linux/pd_warming.h>
> +
> +struct pd_warming_device {
> +       struct thermal_cooling_device *cdev;
> +       struct device dev;
> +       int id;
> +       int max_state;
> +       int cur_state;
> +       bool runtime_resumed;
> +};
> +
> +static DEFINE_IDA(pd_ida);
> +
> +static int pd_wdev_get_max_state(struct thermal_cooling_device *cdev,
> +                                unsigned long *state)
> +{
> +       struct pd_warming_device *pd_wdev = cdev->devdata;
> +
> +       *state = pd_wdev->max_state;
> +       return 0;
> +}
> +
> +static int pd_wdev_get_cur_state(struct thermal_cooling_device *cdev,
> +                                unsigned long *state)
> +{
> +       struct pd_warming_device *pd_wdev = cdev->devdata;
> +
> +       *state = dev_pm_genpd_get_performance_state(&pd_wdev->dev);
> +
> +       return 0;
> +}
> +
> +static int pd_wdev_set_cur_state(struct thermal_cooling_device *cdev,
> +                                unsigned long state)
> +{
> +       struct pd_warming_device *pd_wdev = cdev->devdata;
> +       struct device *dev = &pd_wdev->dev;
> +       int ret;
> +
> +       ret = dev_pm_genpd_set_performance_state(dev, state);
> +
> +       if (ret)
> +               return ret;
> +
> +       if (state && !pd_wdev->runtime_resumed) {
> +               ret = pm_runtime_get_sync(dev);
> +               pd_wdev->runtime_resumed = true;
> +       } else if (!state && pd_wdev->runtime_resumed) {
> +               ret = pm_runtime_put(dev);
> +               pd_wdev->runtime_resumed = false;
> +       }
> +
> +       return ret;
> +}
> +
> +static struct thermal_cooling_device_ops pd_warming_device_ops = {
> +       .get_max_state  = pd_wdev_get_max_state,
> +       .get_cur_state  = pd_wdev_get_cur_state,
> +       .set_cur_state  = pd_wdev_set_cur_state,
> +};
> +
> +static void pd_warming_release(struct device *dev)
> +{
> +       kfree(dev);

This is wrong, you should free a "struct pd_warming_device *". Use the
"container of" macro to get it from 'dev'.

> +}
> +
> +struct thermal_cooling_device *
> +of_pd_warming_register(struct device *parent, int pd_id)
> +{
> +       struct pd_warming_device *pd_wdev;
> +       struct of_phandle_args pd_args;
> +       char cdev_name[THERMAL_NAME_LENGTH];
> +       int ret;
> +
> +       pd_wdev = kzalloc(sizeof(*pd_wdev), GFP_KERNEL);
> +       if (!pd_wdev)
> +               return ERR_PTR(-ENOMEM);
> +
> +       dev_set_name(&pd_wdev->dev, "%s_%d_warming_dev",
> +                    dev_name(parent), pd_id);
> +       pd_wdev->dev.parent = parent;
> +       pd_wdev->dev.release = pd_warming_release;
> +
> +       ret = device_register(&pd_wdev->dev);
> +       if (ret) {
> +               put_device(&pd_wdev->dev);
> +               goto free_pd_wdev;
> +       }
> +
> +       ret = ida_simple_get(&pd_ida, 0, 0, GFP_KERNEL);
> +       if (ret < 0)
> +               goto unregister_device;

If you use and ida, you might as well use it as a part of the
dev_set_name() above.

That should give you a unique name, similar to how you use it for the
cdev_name below.

> +
> +       pd_wdev->id = ret;
> +
> +       pd_args.np = parent->of_node;
> +       pd_args.args[0] = pd_id;
> +       pd_args.args_count = 1;
> +
> +       ret = of_genpd_add_device(&pd_args, &pd_wdev->dev);
> +
> +       if (ret)
> +               goto remove_ida;
> +
> +       ret = dev_pm_genpd_performance_state_count(&pd_wdev->dev);
> +       if (ret < 0)
> +               goto out_genpd;
> +
> +       pd_wdev->max_state = ret - 1;
> +       pm_runtime_enable(&pd_wdev->dev);
> +       pd_wdev->runtime_resumed = false;
> +
> +       snprintf(cdev_name, sizeof(cdev_name), "thermal-pd-%d", pd_wdev->id);
> +       pd_wdev->cdev = thermal_of_cooling_device_register
> +                                       (NULL, cdev_name, pd_wdev,
> +                                        &pd_warming_device_ops);
> +       if (IS_ERR(pd_wdev->cdev)) {
> +               pr_err("unable to register %s cooling device\n", cdev_name);
> +               ret = PTR_ERR(pd_wdev->cdev);
> +               goto out_runtime_disable;
> +       }
> +
> +       return pd_wdev->cdev;
> +
> +out_runtime_disable:
> +       pm_runtime_disable(&pd_wdev->dev);
> +out_genpd:
> +       pm_genpd_remove_device(&pd_wdev->dev);
> +remove_ida:
> +       ida_simple_remove(&pd_ida, pd_wdev->id);
> +unregister_device:
> +       device_unregister(&pd_wdev->dev);
> +       pd_warming_release(&pd_wdev->dev);

This is wrong, drop this.

> +free_pd_wdev:
> +       kfree(pd_wdev);

Since you should free this from the ->release() callback, there is no
need to do this here.

> +       return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL_GPL(of_pd_warming_register);
> +
> +void pd_warming_unregister(struct thermal_cooling_device *cdev)
> +{
> +       struct pd_warming_device *pd_wdev = cdev->devdata;
> +       struct device *dev = &pd_wdev->dev;
> +
> +       if (pd_wdev->runtime_resumed) {
> +               dev_pm_genpd_set_performance_state(dev, 0);
> +               pm_runtime_put(dev);
> +               pd_wdev->runtime_resumed = false;
> +       }
> +       pm_runtime_disable(dev);
> +       pm_genpd_remove_device(dev);
> +       ida_simple_remove(&pd_ida, pd_wdev->id);
> +       thermal_cooling_device_unregister(cdev);
> +       kfree(pd_wdev);

Don't use kfree here, but instead device_unregister(dev);

> +}
> +EXPORT_SYMBOL_GPL(pd_warming_unregister);
> diff --git a/include/linux/pd_warming.h b/include/linux/pd_warming.h
> new file mode 100644
> index 000000000000..550a5683b56d
> --- /dev/null
> +++ b/include/linux/pd_warming.h
> @@ -0,0 +1,29 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2019, Linaro Ltd.
> + */
> +#ifndef __PWR_DOMAIN_WARMING_H__
> +#define __PWR_DOMAIN_WARMING_H__
> +
> +#include <linux/pm_domain.h>
> +#include <linux/thermal.h>
> +
> +#ifdef CONFIG_PWR_DOMAIN_WARMING_THERMAL
> +struct thermal_cooling_device *
> +of_pd_warming_register(struct device *parent, int pd_id);
> +
> +void pd_warming_unregister(struct thermal_cooling_device *cdev);
> +
> +#else
> +static inline struct thermal_cooling_device *
> +of_pd_warming_register(struct device *parent, int pd_id)
> +{
> +       return ERR_PTR(-ENOSYS);
> +}
> +
> +static inline void
> +pd_warming_unregister(struct thermal_cooling_device *cdev)
> +{
> +}
> +#endif /* CONFIG_PWR_DOMAIN_WARMING_THERMAL */
> +#endif /* __PWR_DOMAIN_WARMING_H__ */
> --
> 2.20.1
>

Besides the few things above, this looks good to me.

Kind regards
Uffe
Thara Gopinath March 25, 2020, 2:35 p.m. UTC | #2
Hi Ulf,
Thanks for the review!

On 3/23/20 11:57 AM, Ulf Hansson wrote:

--snip
>> +
>> +static void pd_warming_release(struct device *dev)
>> +{
>> +       kfree(dev);
> 
> This is wrong, you should free a "struct pd_warming_device *". Use the
> "container of" macro to get it from 'dev'.

Will fix this.
> 
>> +}
>> +
>> +struct thermal_cooling_device *
>> +of_pd_warming_register(struct device *parent, int pd_id)
>> +{
>> +       struct pd_warming_device *pd_wdev;
>> +       struct of_phandle_args pd_args;
>> +       char cdev_name[THERMAL_NAME_LENGTH];
>> +       int ret;
>> +
>> +       pd_wdev = kzalloc(sizeof(*pd_wdev), GFP_KERNEL);
>> +       if (!pd_wdev)
>> +               return ERR_PTR(-ENOMEM);
>> +
>> +       dev_set_name(&pd_wdev->dev, "%s_%d_warming_dev",
>> +                    dev_name(parent), pd_id);
>> +       pd_wdev->dev.parent = parent;
>> +       pd_wdev->dev.release = pd_warming_release;
>> +
>> +       ret = device_register(&pd_wdev->dev);
>> +       if (ret) {
>> +               put_device(&pd_wdev->dev);
>> +               goto free_pd_wdev;
>> +       }
>> +
>> +       ret = ida_simple_get(&pd_ida, 0, 0, GFP_KERNEL);
>> +       if (ret < 0)
>> +               goto unregister_device;
> 
> If you use and ida, you might as well use it as a part of the
> dev_set_name() above.
> 
> That should give you a unique name, similar to how you use it for the
> cdev_name below.

dev_set_name above already has a unique name with the power controller 
name and the power domain id. cdev on the other hand creates a virtual 
thermal device and needs a unique name.

> 
>> +
>> +       pd_wdev->id = ret;
>> +
>> +       pd_args.np = parent->of_node;
>> +       pd_args.args[0] = pd_id;
>> +       pd_args.args_count = 1;
>> +
>> +       ret = of_genpd_add_device(&pd_args, &pd_wdev->dev);
>> +
>> +       if (ret)
>> +               goto remove_ida;
>> +
>> +       ret = dev_pm_genpd_performance_state_count(&pd_wdev->dev);
>> +       if (ret < 0)
>> +               goto out_genpd;
>> +
>> +       pd_wdev->max_state = ret - 1;
>> +       pm_runtime_enable(&pd_wdev->dev);
>> +       pd_wdev->runtime_resumed = false;
>> +
>> +       snprintf(cdev_name, sizeof(cdev_name), "thermal-pd-%d", pd_wdev->id);
>> +       pd_wdev->cdev = thermal_of_cooling_device_register
>> +                                       (NULL, cdev_name, pd_wdev,
>> +                                        &pd_warming_device_ops);
>> +       if (IS_ERR(pd_wdev->cdev)) {
>> +               pr_err("unable to register %s cooling device\n", cdev_name);
>> +               ret = PTR_ERR(pd_wdev->cdev);
>> +               goto out_runtime_disable;
>> +       }
>> +
>> +       return pd_wdev->cdev;
>> +
>> +out_runtime_disable:
>> +       pm_runtime_disable(&pd_wdev->dev);
>> +out_genpd:
>> +       pm_genpd_remove_device(&pd_wdev->dev);
>> +remove_ida:
>> +       ida_simple_remove(&pd_ida, pd_wdev->id);
>> +unregister_device:
>> +       device_unregister(&pd_wdev->dev);
>> +       pd_warming_release(&pd_wdev->dev);
> 
> This is wrong, drop this.

Oops . sorry . Will do. Will fix rest of the comments below as well.

> 
>> +free_pd_wdev:
>> +       kfree(pd_wdev);
> 
> Since you should free this from the ->release() callback, there is no
> need to do this here.
> 
>> +       return ERR_PTR(ret);
>> +}
>> +EXPORT_SYMBOL_GPL(of_pd_warming_register);
>> +
>> +void pd_warming_unregister(struct thermal_cooling_device *cdev)
>> +{
>> +       struct pd_warming_device *pd_wdev = cdev->devdata;
>> +       struct device *dev = &pd_wdev->dev;
>> +
>> +       if (pd_wdev->runtime_resumed) {
>> +               dev_pm_genpd_set_performance_state(dev, 0);
>> +               pm_runtime_put(dev);
>> +               pd_wdev->runtime_resumed = false;
>> +       }
>> +       pm_runtime_disable(dev);
>> +       pm_genpd_remove_device(dev);
>> +       ida_simple_remove(&pd_ida, pd_wdev->id);
>> +       thermal_cooling_device_unregister(cdev);
>> +       kfree(pd_wdev);
> 
> Don't use kfree here, but instead device_unregister(dev);
> 
>> +}
>> +EXPORT_SYMBOL_GPL(pd_warming_unregister);
>> diff --git a/include/linux/pd_warming.h b/include/linux/pd_warming.h
>> new file mode 100644
>> index 000000000000..550a5683b56d
>> --- /dev/null
>> +++ b/include/linux/pd_warming.h
>> @@ -0,0 +1,29 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (c) 2019, Linaro Ltd.
>> + */
>> +#ifndef __PWR_DOMAIN_WARMING_H__
>> +#define __PWR_DOMAIN_WARMING_H__
>> +
>> +#include <linux/pm_domain.h>
>> +#include <linux/thermal.h>
>> +
>> +#ifdef CONFIG_PWR_DOMAIN_WARMING_THERMAL
>> +struct thermal_cooling_device *
>> +of_pd_warming_register(struct device *parent, int pd_id);
>> +
>> +void pd_warming_unregister(struct thermal_cooling_device *cdev);
>> +
>> +#else
>> +static inline struct thermal_cooling_device *
>> +of_pd_warming_register(struct device *parent, int pd_id)
>> +{
>> +       return ERR_PTR(-ENOSYS);
>> +}
>> +
>> +static inline void
>> +pd_warming_unregister(struct thermal_cooling_device *cdev)
>> +{
>> +}
>> +#endif /* CONFIG_PWR_DOMAIN_WARMING_THERMAL */
>> +#endif /* __PWR_DOMAIN_WARMING_H__ */
>> --
>> 2.20.1
>>
> 
> Besides the few things above, this looks good to me.
> 
> Kind regards
> Uffe
>

Patch
diff mbox series

diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
index 4d6753f2b18f..92522d541d0e 100644
--- a/drivers/thermal/Kconfig
+++ b/drivers/thermal/Kconfig
@@ -206,6 +206,16 @@  config DEVFREQ_THERMAL
 
 	  If you want this support, you should say Y here.
 
+config PWR_DOMAIN_WARMING_THERMAL
+	bool "Power Domain based warming device"
+	depends on PM_GENERIC_DOMAINS_OF
+	help
+	  This implements the generic power domain based warming
+	  mechanism through increasing the performance state of
+	  a power domain.
+
+	  If you want this support, you should say Y here.
+
 config THERMAL_EMULATION
 	bool "Thermal emulation mode support"
 	help
diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
index 8c8ed7b79915..7db87a779126 100644
--- a/drivers/thermal/Makefile
+++ b/drivers/thermal/Makefile
@@ -28,6 +28,8 @@  thermal_sys-$(CONFIG_CLOCK_THERMAL)	+= clock_cooling.o
 # devfreq cooling
 thermal_sys-$(CONFIG_DEVFREQ_THERMAL) += devfreq_cooling.o
 
+thermal_sys-$(CONFIG_PWR_DOMAIN_WARMING_THERMAL)	+= pd_warming.o
+
 # platform thermal drivers
 obj-y				+= broadcom/
 obj-$(CONFIG_THERMAL_MMIO)		+= thermal_mmio.o
diff --git a/drivers/thermal/pd_warming.c b/drivers/thermal/pd_warming.c
new file mode 100644
index 000000000000..c0854d2e4b92
--- /dev/null
+++ b/drivers/thermal/pd_warming.c
@@ -0,0 +1,168 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2019, Linaro Ltd
+ */
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/module.h>
+#include <linux/pm_runtime.h>
+#include <linux/slab.h>
+#include <linux/pd_warming.h>
+
+struct pd_warming_device {
+	struct thermal_cooling_device *cdev;
+	struct device dev;
+	int id;
+	int max_state;
+	int cur_state;
+	bool runtime_resumed;
+};
+
+static DEFINE_IDA(pd_ida);
+
+static int pd_wdev_get_max_state(struct thermal_cooling_device *cdev,
+				 unsigned long *state)
+{
+	struct pd_warming_device *pd_wdev = cdev->devdata;
+
+	*state = pd_wdev->max_state;
+	return 0;
+}
+
+static int pd_wdev_get_cur_state(struct thermal_cooling_device *cdev,
+				 unsigned long *state)
+{
+	struct pd_warming_device *pd_wdev = cdev->devdata;
+
+	*state = dev_pm_genpd_get_performance_state(&pd_wdev->dev);
+
+	return 0;
+}
+
+static int pd_wdev_set_cur_state(struct thermal_cooling_device *cdev,
+				 unsigned long state)
+{
+	struct pd_warming_device *pd_wdev = cdev->devdata;
+	struct device *dev = &pd_wdev->dev;
+	int ret;
+
+	ret = dev_pm_genpd_set_performance_state(dev, state);
+
+	if (ret)
+		return ret;
+
+	if (state && !pd_wdev->runtime_resumed) {
+		ret = pm_runtime_get_sync(dev);
+		pd_wdev->runtime_resumed = true;
+	} else if (!state && pd_wdev->runtime_resumed) {
+		ret = pm_runtime_put(dev);
+		pd_wdev->runtime_resumed = false;
+	}
+
+	return ret;
+}
+
+static struct thermal_cooling_device_ops pd_warming_device_ops = {
+	.get_max_state	= pd_wdev_get_max_state,
+	.get_cur_state	= pd_wdev_get_cur_state,
+	.set_cur_state	= pd_wdev_set_cur_state,
+};
+
+static void pd_warming_release(struct device *dev)
+{
+	kfree(dev);
+}
+
+struct thermal_cooling_device *
+of_pd_warming_register(struct device *parent, int pd_id)
+{
+	struct pd_warming_device *pd_wdev;
+	struct of_phandle_args pd_args;
+	char cdev_name[THERMAL_NAME_LENGTH];
+	int ret;
+
+	pd_wdev = kzalloc(sizeof(*pd_wdev), GFP_KERNEL);
+	if (!pd_wdev)
+		return ERR_PTR(-ENOMEM);
+
+	dev_set_name(&pd_wdev->dev, "%s_%d_warming_dev",
+		     dev_name(parent), pd_id);
+	pd_wdev->dev.parent = parent;
+	pd_wdev->dev.release = pd_warming_release;
+
+	ret = device_register(&pd_wdev->dev);
+	if (ret) {
+		put_device(&pd_wdev->dev);
+		goto free_pd_wdev;
+	}
+
+	ret = ida_simple_get(&pd_ida, 0, 0, GFP_KERNEL);
+	if (ret < 0)
+		goto unregister_device;
+
+	pd_wdev->id = ret;
+
+	pd_args.np = parent->of_node;
+	pd_args.args[0] = pd_id;
+	pd_args.args_count = 1;
+
+	ret = of_genpd_add_device(&pd_args, &pd_wdev->dev);
+
+	if (ret)
+		goto remove_ida;
+
+	ret = dev_pm_genpd_performance_state_count(&pd_wdev->dev);
+	if (ret < 0)
+		goto out_genpd;
+
+	pd_wdev->max_state = ret - 1;
+	pm_runtime_enable(&pd_wdev->dev);
+	pd_wdev->runtime_resumed = false;
+
+	snprintf(cdev_name, sizeof(cdev_name), "thermal-pd-%d", pd_wdev->id);
+	pd_wdev->cdev = thermal_of_cooling_device_register
+					(NULL, cdev_name, pd_wdev,
+					 &pd_warming_device_ops);
+	if (IS_ERR(pd_wdev->cdev)) {
+		pr_err("unable to register %s cooling device\n", cdev_name);
+		ret = PTR_ERR(pd_wdev->cdev);
+		goto out_runtime_disable;
+	}
+
+	return pd_wdev->cdev;
+
+out_runtime_disable:
+	pm_runtime_disable(&pd_wdev->dev);
+out_genpd:
+	pm_genpd_remove_device(&pd_wdev->dev);
+remove_ida:
+	ida_simple_remove(&pd_ida, pd_wdev->id);
+unregister_device:
+	device_unregister(&pd_wdev->dev);
+	pd_warming_release(&pd_wdev->dev);
+free_pd_wdev:
+	kfree(pd_wdev);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(of_pd_warming_register);
+
+void pd_warming_unregister(struct thermal_cooling_device *cdev)
+{
+	struct pd_warming_device *pd_wdev = cdev->devdata;
+	struct device *dev = &pd_wdev->dev;
+
+	if (pd_wdev->runtime_resumed) {
+		dev_pm_genpd_set_performance_state(dev, 0);
+		pm_runtime_put(dev);
+		pd_wdev->runtime_resumed = false;
+	}
+	pm_runtime_disable(dev);
+	pm_genpd_remove_device(dev);
+	ida_simple_remove(&pd_ida, pd_wdev->id);
+	thermal_cooling_device_unregister(cdev);
+	kfree(pd_wdev);
+}
+EXPORT_SYMBOL_GPL(pd_warming_unregister);
diff --git a/include/linux/pd_warming.h b/include/linux/pd_warming.h
new file mode 100644
index 000000000000..550a5683b56d
--- /dev/null
+++ b/include/linux/pd_warming.h
@@ -0,0 +1,29 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2019, Linaro Ltd.
+ */
+#ifndef __PWR_DOMAIN_WARMING_H__
+#define __PWR_DOMAIN_WARMING_H__
+
+#include <linux/pm_domain.h>
+#include <linux/thermal.h>
+
+#ifdef CONFIG_PWR_DOMAIN_WARMING_THERMAL
+struct thermal_cooling_device *
+of_pd_warming_register(struct device *parent, int pd_id);
+
+void pd_warming_unregister(struct thermal_cooling_device *cdev);
+
+#else
+static inline struct thermal_cooling_device *
+of_pd_warming_register(struct device *parent, int pd_id)
+{
+	return ERR_PTR(-ENOSYS);
+}
+
+static inline void
+pd_warming_unregister(struct thermal_cooling_device *cdev)
+{
+}
+#endif /* CONFIG_PWR_DOMAIN_WARMING_THERMAL */
+#endif /* __PWR_DOMAIN_WARMING_H__ */