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Date: Fri, 3 Jul 2020 12:02:10 +0200
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: Thara Gopinath <thara.gopinath@...aro.org>, rui.zhang@...el.com,
ulf.hansson@...aro.org, bjorn.andersson@...aro.org,
agross@...nel.org, robh@...nel.org
Cc: amit.kucheria@...durent.com, mark.rutland@....com,
rjw@...ysocki.net, linux-pm@...r.kernel.org,
devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
linux-kernel@...r.kernel.org, Lukasz Luba <Lukasz.Luba@....com>
Subject: Re: [PATCH v6 3/6] thermal: Add generic power domain warming device
driver.
Hi Thara,
sorry for the delay.
Added Lukasz.
On 04/06/2020 03:53, Thara Gopinath 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).
The patch itself looks fine but I'm not very convinced about using a
specific driver as a warming device.
It is all about changing the performance state of a device and the power
domain is a way to access the associated callback.
It could be used as a cooling device as well.
The cpufreq cooling device could be used as a warming device and the way
we access the performance state is the freq qos.
We end up with different ways to do the same thing : change the
performance state.
On the other side, the energy model is being moved to the struct device,
so we will have gpu and cpu using it to retrieve a performance state
given a power value.
My opinion is instead of multiplying the ways to do the same think, we
should find a way to unify all the passive cooling devices into a single
generic performance state based mitigation device.
It does not imply to make all the passive cooling device changes but
provide a generic one first.
The ideal would be to register a struct device as a performance state
capable device and use the energy model stored in it.
In the meantime, the energy model should embed a couple of callbacks
get_power / set_power to set the performance state.
That implies a bit of more work, but IMHO it is worth to do.
Does it make sense ?
> ---
>
> 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.
> v5->v6:
> - Fixed issues with ->release() and kfree(dev) as pointed
> out by Ulf.
>
> drivers/thermal/Kconfig | 10 +++
> drivers/thermal/Makefile | 4 +
> drivers/thermal/pd_warming.c | 169 +++++++++++++++++++++++++++++++++++
> include/linux/pd_warming.h | 29 ++++++
> 4 files changed, 212 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 e53314ea9e25..3a0bcf3e8bd9 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 86c506410cc0..14fa696a08bd 100644
> --- a/drivers/thermal/Makefile
> +++ b/drivers/thermal/Makefile
> @@ -28,7 +28,11 @@ thermal_sys-$(CONFIG_CLOCK_THERMAL) += clock_cooling.o
> # devfreq cooling
> thermal_sys-$(CONFIG_DEVFREQ_THERMAL) += devfreq_cooling.o
>
> +#pwr domain warming
> +thermal_sys-$(CONFIG_PWR_DOMAIN_WARMING_THERMAL) += pd_warming.o
> +
> obj-$(CONFIG_K3_THERMAL) += k3_bandgap.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..1ea93481c79b
> --- /dev/null
> +++ b/drivers/thermal/pd_warming.c
> @@ -0,0 +1,169 @@
> +// 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)
> +{
> + struct pd_warming_device *pd_wdev;
> +
> + pd_wdev = container_of(dev, struct pd_warming_device, dev);
> + kfree(pd_wdev);
> +}
> +
> +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 out;
> + }
> +
> + 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);
> +out:
> + 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);
> + 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__ */
>
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