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Date: Mon, 8 Mar 2021 09:53:54 +0000
From: Lukasz Luba <lukasz.luba@....com>
To: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: cwchoi00@...il.com, linux-kernel@...r.kernel.org,
linux-pm@...r.kernel.org, steven.price@....com,
MyungJoo Ham <myungjoo.ham@...sung.com>,
Kyungmin Park <kyungmin.park@...sung.com>,
Chanwoo Choi <cw00.choi@...sung.com>
Subject: Re: [PATCH v5 1/4] PM / devfreq: Register devfreq as a cooling device
on demand
Hi Daniel,
In general the approach is good. If there is a special GPU driver, which
would like to provide 'struct devfreq_cooling_power *' it would leave
'is_cooling_device=false' and register manually:
devfreq_cooling_em_register(df, dfc_power);
Please find only a few minor comments below.
On 3/8/21 9:16 AM, Daniel Lezcano wrote:
> Currently the default behavior is to manually having the devfreq
> backend to register themselves as a devfreq cooling device.
>
> Instead of adding the code in the drivers for the thermal cooling
> device registering, let's provide a flag in the devfreq's profile to
> tell the common devfreq code to register the newly created devfreq as
> a cooling device.
>
> Suggested-by: Chanwoo Choi <cwchoi00@...il.com>
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> ---
> V5:
> - Changed subject prefix by: PM / devfreq
> V4:
> - Replaced thermal_cooling_device_unregister() by
> devfreq_cooling_unregister()
> V3:
> - Rebased on linux-pm branch without units.h
> - Set the cdev to NULL in case of error
> - Added description for the cdev field in the devfreq structure
> V2:
> - Added is_cooling_device boolean in profile structure
> - Register cooling device when the is_cooling_device boolean is set
> - Remove devfreq cooling device registration in the backend drivers
> V1:
> - Register devfreq as a cooling device unconditionnally
> ---
> drivers/devfreq/devfreq.c | 13 +++++++++++++
> include/linux/devfreq.h | 8 ++++++++
> 2 files changed, 21 insertions(+)
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index bf3047896e41..8a535d4d6083 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -11,6 +11,7 @@
> #include <linux/kmod.h>
> #include <linux/sched.h>
> #include <linux/debugfs.h>
> +#include <linux/devfreq_cooling.h>
> #include <linux/errno.h>
> #include <linux/err.h>
> #include <linux/init.h>
> @@ -26,6 +27,7 @@
> #include <linux/hrtimer.h>
> #include <linux/of.h>
> #include <linux/pm_qos.h>
> +#include <linux/thermal.h>
Since the unregister is now called from devfreq_cooling.h, this header
here is not needed. It might rather be moved into the devfreq.h
where there is this new field: 'cdev' if we are going to use something
from it.
> #include "governor.h"
>
> #define CREATE_TRACE_POINTS
> @@ -935,6 +937,15 @@ struct devfreq *devfreq_add_device(struct device *dev,
>
> mutex_unlock(&devfreq_list_lock);
>
> + if (devfreq->profile->is_cooling_device) {
> + devfreq->cdev = devfreq_cooling_em_register(devfreq, NULL);
> + if (IS_ERR(devfreq->cdev)) {
> + dev_info(dev, "Failed to register devfreq "
> + "cooling device\n");
I would skip this print. Not every kernel config has DEVFREQ_THERMAL set
and the value ERR_PTR(-EINVAL) from header would be returned in such
case.
Inside the devfreq_cooling_em_register() (and others) there are prints
showing that something wrong happen and would be triggered if compiled.
> + devfreq->cdev = NULL;
> + }
> + }
> +
> return devfreq;
>
> err_init:
> @@ -960,6 +971,8 @@ int devfreq_remove_device(struct devfreq *devfreq)
> if (!devfreq)
> return -EINVAL;
>
> + devfreq_cooling_unregister(devfreq->cdev);
> +
> if (devfreq->governor) {
> devfreq->governor->event_handler(devfreq,
> DEVFREQ_GOV_STOP, NULL);
> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> index 26ea0850be9b..aba7ace11b72 100644
> --- a/include/linux/devfreq.h
> +++ b/include/linux/devfreq.h
> @@ -98,11 +98,15 @@ struct devfreq_dev_status {
> * @freq_table: Optional list of frequencies to support statistics
> * and freq_table must be generated in ascending order.
> * @max_state: The size of freq_table.
> + *
> + * @is_cooling_device: A self-explanatory boolean giving the device a
> + * cooling effect property.
> */
> struct devfreq_dev_profile {
> unsigned long initial_freq;
> unsigned int polling_ms;
> enum devfreq_timer timer;
> + bool is_cooling_device;
>
> int (*target)(struct device *dev, unsigned long *freq, u32 flags);
> int (*get_dev_status)(struct device *dev,
> @@ -156,6 +160,7 @@ struct devfreq_stats {
> * @suspend_count: suspend requests counter for a device.
> * @stats: Statistics of devfreq device behavior
> * @transition_notifier_list: list head of DEVFREQ_TRANSITION_NOTIFIER notifier
> + * @cdev: Cooling device pointer if the devfreq has cooling property
> * @nb_min: Notifier block for DEV_PM_QOS_MIN_FREQUENCY
> * @nb_max: Notifier block for DEV_PM_QOS_MAX_FREQUENCY
> *
> @@ -198,6 +203,9 @@ struct devfreq {
>
> struct srcu_notifier_head transition_notifier_list;
>
> + /* Pointer to the cooling device if used for thermal mitigation */
> + struct thermal_cooling_device *cdev;
The linux/thermal.h for 'cdev' would be needed in this header.
> +
> struct notifier_block nb_min;
> struct notifier_block nb_max;
> };
>
With this small changes:
Reviewed-by: Lukasz Luba <lukasz.luba@....com>
Regards,
Lukasz
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