Messages in this thread | | | Date | Wed, 21 Sep 2022 21:15:54 +0800 | Subject | Re: [RESEND] devfreq: governor: Save void *data in the governor userspace | From | Kant Fan <> |
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On 9/15/2022 3:41 PM, Kant Fan wrote: >>>> static int devfreq_userspace_handler(struct devfreq *devfreq, >>> >>> Dear MyungJoo, Kyungmin & Chanwoo, >>> Gently ping this issue... Does this patch has a chance to be accepted? >>> This seems to be a bug in devfreq userspace governor, which affects the >>> switching between governors -- When switching from userspace to >>> ondemand, the ondemand governor would be invalid. >>> If there's any question, please let me know. >>> Thank you. >> >> Yes, indeed. This is a bug. >> >> Actually, it appears that allocating a new memory buffer for >> devfreq->data itself is a bug for a governor, this is supposed >> to be allocated by a device driver. Thus, the comment of >> "void *data" of "struct devfreq" should be updated: >> "/* private data for governors given by device drivers */" >> >> It'd be better to have something like, "void *internal_data" >> for governors to freely handle within its context of init-exit, >> which is not touched by its users (device drivers). >> >> @Chanwoo: what's your opinion on this? >> >> Cheers, >> MyungJoo. >> > > Hi MyungJoo, > Thanks for your suggestion. Here's the patch-v2, please have a look: > > -- > Subject: [PATCH] devfreq: governor: Add a private governor_data for > governors in devfreq > > The member void *data in the structure devfreq can be overwrite > by governor_userspace. For example: > 1. The device driver assigned the devfreq governor to simple_ondemand > by the function devfreq_add_device() and init the devfreq member > void *data to a pointer of a static structure devfreq_simple_ondemand_data > by the function devfreq_add_device(). > 2. The user changed the devfreq governor to userspace by the command > "echo userspace > /sys/class/devfreq/.../governor". > 3. The governor userspace alloced a dynamic memory for the struct > userspace_data and assigend the member void *data of devfreq to > this memory by the function userspace_init(). > 4. The user changed the devfreq governor back to simple_ondemand > by the command "echo simple_ondemand > /sys/class/devfreq/.../governor". > 5. The governor userspace exited and assigned the member void *data > in the structure devfreq to NULL by the function userspace_exit(). > 6. The governor simple_ondemand fetched the static information of > devfreq_simple_ondemand_data in the function > devfreq_simple_ondemand_func() but the member void *data of devfreq was > assigned to NULL by the function userspace_exit(). > 7. The information of upthreshold and downdifferential is lost > and the governor simple_ondemand can't work correctly. > > The member void *data in the structure devfreq is designed for > a static pointer used in a governor and inited by the function > devfreq_add_device(). This patch add an element named governor_data > in the devfreq structure which can be used by a governor(E.g userspace) > who want to assign a private data to do some private things. > > Signed-off-by: Kant Fan <kant@allwinnertech.com> > --- > > diff --git a/drivers/devfreq/governor_userspace.c > b/drivers/devfreq/governor_userspace.c > index ab9db7a..d69672c 100644 > --- a/drivers/devfreq/governor_userspace.c > +++ b/drivers/devfreq/governor_userspace.c > @@ -21,7 +21,7 @@ > > static int devfreq_userspace_func(struct devfreq *df, unsigned long > *freq) > { > - struct userspace_data *data = df->data; > + struct userspace_data *data = df->governor_data; > > if (data->valid) > *freq = data->user_frequency; > @@ -40,7 +40,7 @@ > int err = 0; > > mutex_lock(&devfreq->lock); > - data = devfreq->data; > + data = devfreq->governor_data; > > sscanf(buf, "%lu", &wanted); > data->user_frequency = wanted; > @@ -60,7 +60,7 @@ > int err = 0; > > mutex_lock(&devfreq->lock); > - data = devfreq->data; > + data = devfreq->governor_data; > > if (data->valid) > err = sprintf(buf, "%lu\n", data->user_frequency); > @@ -91,7 +91,7 @@ > goto out; > } > data->valid = false; > - devfreq->data = data; > + devfreq->governor_data = data; > > err = sysfs_create_group(&devfreq->dev.kobj, &dev_attr_group); > out: > @@ -107,8 +107,8 @@ > if (devfreq->dev.kobj.sd) > sysfs_remove_group(&devfreq->dev.kobj, &dev_attr_group); > > - kfree(devfreq->data); > - devfreq->data = NULL; > + kfree(devfreq->governor_data); > + devfreq->governor_data = NULL; > } > > static int devfreq_userspace_handler(struct devfreq *devfreq, > diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h > index 34aab4d..d265af3 100644 > --- a/include/linux/devfreq.h > +++ b/include/linux/devfreq.h > @@ -152,8 +152,8 @@ > * @max_state: count of entry present in the frequency table. > * @previous_freq: previously configured frequency value. > * @last_status: devfreq user device info, performance statistics > - * @data: Private data of the governor. The devfreq framework does not > - * touch this. > + * @data: devfreq core pass to governors, governor should not change > it. > + * @governor_data: private data for governors, devfreq core doesn't > touch it. > * @user_min_freq_req: PM QoS minimum frequency request from user > (via sysfs) > * @user_max_freq_req: PM QoS maximum frequency request from user > (via sysfs) > * @scaling_min_freq: Limit minimum frequency requested by OPP > interface > @@ -193,7 +193,8 @@ > unsigned long previous_freq; > struct devfreq_dev_status last_status; > > - void *data; /* private data for governors */ > + void *data; > + void *governor_data; > > struct dev_pm_qos_request user_min_freq_req; > struct dev_pm_qos_request user_max_freq_req; >
Hi MyungJoo, Sorry to disturb. Just want to say that I'm looking forward to your advice on this patch. Thank you :>
-- Best Regards, Kant Fan
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