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Message-ID: <5DA88CB8.6050206@linaro.org>
Date: Thu, 17 Oct 2019 11:46:00 -0400
From: Thara Gopinath <thara.gopinath@...aro.org>
To: Ulf Hansson <ulf.hansson@...aro.org>
Cc: Eduardo Valentin <edubezval@...il.com>,
Zhang Rui <rui.zhang@...el.com>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
Bjorn Andersson <bjorn.andersson@...aro.org>,
Andy Gross <agross@...nel.org>, amit.kucheria@...durent.com,
Mark Rutland <mark.rutland@....com>,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
Linux PM <linux-pm@...r.kernel.org>,
DTML <devicetree@...r.kernel.org>,
linux-arm-msm <linux-arm-msm@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 4/7] thermal: Add generic power domain warming device
driver.
On 10/17/2019 04:47 AM, Ulf Hansson wrote:
> On Wed, 16 Oct 2019 at 21:37, Thara Gopinath <thara.gopinath@...aro.org> wrote:
>>
>> Resources modeled as power domains in linux kenrel
>> 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@...aro.org>
>> ---
>> drivers/thermal/Kconfig | 10 +++
>> drivers/thermal/Makefile | 2 +
>> drivers/thermal/pwr_domain_warming.c | 136 +++++++++++++++++++++++++++++++++++
>> include/linux/pwr_domain_warming.h | 31 ++++++++
>> 4 files changed, 179 insertions(+)
>> create mode 100644 drivers/thermal/pwr_domain_warming.c
>> create mode 100644 include/linux/pwr_domain_warming.h
>>
>> diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
>> index 001a21a..0c5c93e 100644
>> --- a/drivers/thermal/Kconfig
>> +++ b/drivers/thermal/Kconfig
>> @@ -187,6 +187,16 @@ 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 74a37c7..382c64a 100644
>> --- a/drivers/thermal/Makefile
>> +++ b/drivers/thermal/Makefile
>> @@ -27,6 +27,8 @@ thermal_sys-$(CONFIG_CLOCK_THERMAL) += clock_cooling.o
>> # devfreq cooling
>> thermal_sys-$(CONFIG_DEVFREQ_THERMAL) += devfreq_cooling.o
>>
>> +thermal_sys-$(CONFIG_PWR_DOMAIN_WARMING_THERMAL) += pwr_domain_warming.o
>> +
>> # platform thermal drivers
>> obj-y += broadcom/
>> obj-$(CONFIG_THERMAL_MMIO) += thermal_mmio.o
>> diff --git a/drivers/thermal/pwr_domain_warming.c b/drivers/thermal/pwr_domain_warming.c
>> new file mode 100644
>> index 0000000..60fae3e
>> --- /dev/null
>> +++ b/drivers/thermal/pwr_domain_warming.c
>> @@ -0,0 +1,136 @@
>> +// 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/pwr_domain_warming.h>
>> +
>> +struct pd_warming_device {
>> + struct thermal_cooling_device *cdev;
>> + struct generic_pm_domain *gpd;
>
> No, this isn't a genpd provider and thus we should not need to carry
> the above pointer in the struct pd_warming_device.
I store this to attach the device in late_init. More about this
approach below.
>
>> + struct device *dev;
>> + int max_state;
>> + int cur_state;
>> + bool runtime_resumed;
>> +};
>> +
>> +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 int pd_wdev_late_init(struct thermal_cooling_device *cdev)
>> +{
>> + struct pd_warming_device *pd_wdev = cdev->devdata;
>> + struct device *dev = &cdev->device;
>> + int state_count, ret;
>> +
>> + ret = pm_genpd_add_device(pd_wdev->gpd, dev);
>
> The pm_genpd_add_device() is a legacy interface and we are striving to
> remove it. I think there are two better options for you to use to deal
> with the attach thingy.
I was not aware of this. Apologies.
>
> 1. The easiest one is probably just to convert into using
> of_genpd_add_device() instead. I think you already have the
> information that you need in the ->cdev pointer to do that. However,
> that also means you need to add the ->late_init() callback to the
> struct thermal_cooling_device_ops, like what you do here.
>
> 2. Maybe the most correct solution is, rather than attaching
> &cdev->device to the PM domain, to register a separate new device
> (device_register()) and assign it the corresponding OF node as the
> genpd provider's subnode and then attach this one instead. If
> "power-domains" can be specified in the subnode, you can even use
> dev_pm_domain_attach() to attach the device to the PM domain, else
> of_genpd_add_device() should work. In the second step, when
> registering the cooling device, the new device above should be
> assigned as parent to the device that is about to be registered via
> thermal_of_cooling_device_register(). In other words, the
> thermal_of_cooling_device_register() needs to be extended to cope with
> receiving a parent device as an in-parameter, but that should be
> doable I think. In this way, you don't need to add the ->late_init()
> callback at all, but you can instead just use the parent device when
> operating on the PM domain.
I did toy with registering a separate device vs reusing cdev device.
My rational was, the power domain is actually controlled/needed by the
cdev and hence should be attached to it.
For me either solution is acceptable . It is a trade off between
creating a new device and registering it as a parent of cooling device
vs introducing a late init. With the second approach I should be able to
do away with the generic_pm_domain pointer in pd_warming_device. To
register a parent for a cooling device, I will have to introduce a new
API in the thermal framework. Like
thermal_of_cooling_device_parent_register. I am ok with this as well.
I would like to hear on what some of the thermal maintainers/reviewers
have to say about both the approaches and which is better.
I will wait a few days for others to review and if there are no major
comments, I will send across the series after updating it to the second
approach.
--
Warm Regards
Thara
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