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Subject: Re: [PATCH 4/5] thermal: Add generic power domain warming device
 driver.
To:     Ulf Hansson <ulf.hansson@linaro.org>
References: <1568135676-9328-1-git-send-email-thara.gopinath@linaro.org>
 <1568135676-9328-5-git-send-email-thara.gopinath@linaro.org>
 <CAPDyKFpzeF6Adu9qBTFazTzbe=rv90x1UjKqC2LvCDpoXBJfVQ@mail.gmail.com>
Cc:     Eduardo Valentin <edubezval@gmail.com>,
        Zhang Rui <rui.zhang@intel.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Rob Herring <robh+dt@kernel.org>, agross@kernel.org,
        amit.kucheria@verdurent.com, Mark Rutland <mark.rutland@arm.com>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Linux PM <linux-pm@vger.kernel.org>,
        DTML <devicetree@vger.kernel.org>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
From:   Thara Gopinath <thara.gopinath@linaro.org>
Message-ID: <5D7AA7F9.1060603@linaro.org>
Date:   Thu, 12 Sep 2019 16:18:01 -0400
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On 09/12/2019 11:04 AM, Ulf Hansson wrote:

Hi Ulf,

Thanks for the review.
> On Tue, 10 Sep 2019 at 19:14, Thara Gopinath <thara.gopinath@linaro.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@linaro.org>
>> ---
>> v1->v2:
>>         - Make power domain based warming device driver a generic
>>         driver in the thermal framework. v1 implemented this as a
>>         Qualcomm specific driver.
>>         - Rename certain variables as per review suggestions on the
>>         mailing list.
>>
>>  drivers/thermal/Kconfig              |  11 +++
>>  drivers/thermal/Makefile             |   2 +
>>  drivers/thermal/pwr_domain_warming.c | 174 +++++++++++++++++++++++++++++++++++
>>  3 files changed, 187 insertions(+)
>>  create mode 100644 drivers/thermal/pwr_domain_warming.c
>>
>> diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
>> index 9966364..eeb6018 100644
>> --- a/drivers/thermal/Kconfig
>> +++ b/drivers/thermal/Kconfig
>> @@ -187,6 +187,17 @@ 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
>> +       depends on PM_GENERIC_DOMAINS_OF
> 
> PM_GENERIC_DOMAINS_OF can't be set unless PM_GENERIC_DOMAINS is set too.
> 
> So I assume it's sufficient to depend on PM_GENERIC_DOMAINS_OF?

Yes, you are right. I will change it.
> 
>> +       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..3dd792b
>> --- /dev/null
>> +++ b/drivers/thermal/pwr_domain_warming.c
>> @@ -0,0 +1,174 @@
>> +// 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_domain.h>
>> +#include <linux/pm_runtime.h>
>> +#include <linux/thermal.h>
>> +
>> +struct pd_warming_device {
>> +       struct thermal_cooling_device *cdev;
>> +       struct device *dev;
>> +       int max_state;
>> +       int cur_state;
>> +       bool runtime_resumed;
>> +};
>> +
>> +static const struct of_device_id pd_wdev_match_table[] = {
>> +       { .compatible = "thermal-power-domain-wdev", .data = NULL },
>> +       { }
>> +};
>> +MODULE_DEVICE_TABLE(of, pd_wdev_match_table);
>> +
>> +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 int pd_wdev_create(struct device *dev, const char *name)
>> +{
>> +       struct pd_warming_device *pd_wdev;
>> +       int state_count;
>> +
>> +       pd_wdev = devm_kzalloc(dev, sizeof(*pd_wdev), GFP_KERNEL);
>> +       if (!pd_wdev)
>> +               return -ENOMEM;
>> +
>> +       state_count = dev_pm_genpd_performance_state_count(dev);
>> +       if (state_count < 0)
>> +               return state_count;
>> +
>> +       pd_wdev->dev = dev;
>> +       pd_wdev->max_state = state_count - 1;
>> +       pd_wdev->runtime_resumed = false;
>> +
>> +       pm_runtime_enable(dev);
>> +
>> +       pd_wdev->cdev = thermal_of_cooling_device_register
>> +                                       (dev->of_node, name,
>> +                                        pd_wdev,
>> +                                        &pd_warming_device_ops);
>> +       if (IS_ERR(pd_wdev->cdev)) {
>> +               dev_err(dev, "unable to register %s cooling device\n", name);
>> +               pm_runtime_disable(dev);
>> +
>> +               return PTR_ERR(pd_wdev->cdev);
>> +       }
>> +
>> +       return 0;
>> +}
>> +
>> +static int pd_wdev_probe(struct platform_device *pdev)
>> +{
>> +       struct device *dev = &pdev->dev, *pd_dev;
>> +       const char *pd_name;
>> +       int id, count, ret = 0;
>> +
>> +       count = of_count_phandle_with_args(dev->of_node, "power-domains",
>> +                                          "#power-domain-cells");
> 
> Perhaps this should be converted to genpd OF helper function instead,
> that allows the caller to know how many power-domains there are
> specified for a device node.

I am ok with this if you think that a OF helper to get the number of
power domains is a useful helper in the genpd framework. I can add it as
part of the next revision. Or do you want me to send it across separate?
> 
>> +
>> +       if (count > 1) {
>> +               for (id = 0; id < count; id++) {
>> +                       ret = of_property_read_string_index
>> +                                       (dev->of_node, "power-domain-names",
>> +                                        id, &pd_name);
>> +                       if (ret) {
>> +                               dev_err(dev, "Error reading the power domain name %d\n", ret);
>> +                               continue;
>> +                       }
> 
> It looks a bit awkward that you want to re-use the power-domain-names
> as the name for the cooling (warming) device. This isn't really what
> we use the "*-names" bindings for in general, I think.
> 
> Anyway, if you want a name corresponding to the actual attached PM
> domain, perhaps re-using "->name" from the struct generic_pm_domain is
> better. We can add a genpd helper for that, no problem. Of course it
> also means that you must call dev_pm_domain_attach_by_id() first, to
> attach the device and then get the name of the genpd, but that should
> be fine.

Ya. I need a name corresponding to the power domain name (or something
very close) to identify the actual warming device in the sysfs entries.
I can use genpd->name and a helper function to achieve it. I can include
it in Patch 1/5 where I add other helper functions.
> 
>> +
>> +                       pd_dev = dev_pm_domain_attach_by_id(dev, id);
>> +                       if (IS_ERR(pd_dev)) {
>> +                               dev_err(dev, "Error attaching power domain %s %ld\n", pd_name, PTR_ERR(pd_dev));
>> +                               continue;
>> +                       }
>> +
>> +                       ret = pd_wdev_create(pd_dev, pd_name);
>> +                       if (ret) {
>> +                               dev_err(dev, "Error building cooling device %s %d\n", pd_name, ret);
>> +                               dev_pm_domain_detach(pd_dev, false);
>> +                               continue;
>> +                       }
> 
> I am wondering about the use case of having multiple PM domains
> attached to the cooling (warming) device. Is that really needed?
> Perhaps you can elaborate on that a bit?
Ya. I though about this as well. I don't have a use case. In my current
case it is just one power domain on the SoC. But considering this is now
a generic driver, in my opinion this has to be a generic solution. So if
you think about this, the device should be able to specify any number of
power domains that can behave as a warming device since a SoC can have
any number of power domain based warming devices. May be one to warm up
the cpus, one for gpus etc.

So another way of implementing this whole thing is to avoid having a
special power domain warming device defined in the device tree. Instead,
add a few new binding to the power-domain controller/provider entries
to specify if a power domain controlled by the provider can act as a
warming device or not. And have the initialization code for the power
domain controller (of_genpd_add_provider_onecell or any other suitable
API) register the specified power domain as a warming device.  The DT
entries should probably look something like below in the case.

rpmhpd: power-controller {
                                compatible = "qcom,sdm845-rpmhpd";
                                #power-domain-cells = <1>;
				hosts-warming-dev;
				warming-dev-names = "mx";
                                operating-points-v2 = <&rpmhpd_opp_table>;

                                rpmhpd_opp_table: opp-table {
                                        compatible = "operating-points-v2";
....

And have the following in of_genpd_add_provider_onecell

if (hosts-warming-dev)
	# loop through the warming-dev-names and register them as power domain
warming devices.

You think this is a better idea?

> 
>> +               }
>> +       } else if (count == 1) {
>> +               ret = of_property_read_string_index(dev->of_node,
>> +                                                   "power-domain-names",
>> +                                                   0, &pd_name);
>> +               if (ret) {
>> +                       dev_err(dev, "Error reading the power domain name %d\n", ret);
>> +                       goto exit;
>> +               }
> 
> According to my comment above, perhaps we simply don't have to use the
> "power-domain-names" binding at all.
I will use genpd->name

> 
> Also, I don't think this is really safe, as there is no guarantee that
> there is PM domain attached to the device, just because you found the
> DT property "power-domain-names".
> 
> Probably better to check pm_domain pointer for the device.
> 
>> +
>> +               ret = pd_wdev_create(dev, pd_name);
>> +               if (ret) {
>> +                       dev_err(dev, "Error building cooling device %s %d\n", pd_name, ret);
>> +                       goto exit;
>> +               }
>> +       } else  {
>> +               ret = -EINVAL;
>> +       }
>> +
>> +exit:
>> +       return ret;
>> +}
>> +
>> +static struct platform_driver pd_wdev_driver = {
>> +       .driver = {
>> +               .name = "qcom-rpmhpd-cdev",
> 
> Probably rename to a more generic name (leftover from earlier version I assume).

Ya. I missed it . Will fix it.
> 
>> +               .of_match_table = pd_wdev_match_table,
>> +       },
>> +       .probe = pd_wdev_probe,
>> +};
>> +module_platform_driver(pd_wdev_driver);
>> +
>> +MODULE_DESCRIPTION("Qualcomm RPMHPD cooling device driver");
> 
> Ditto.

Will fix it.
> 
>> +MODULE_LICENSE("GPL v2");
>> --
>> 2.1.4
>>
> 
> Kind regards
> Uffe
> 


-- 
Warm Regards
Thara