Re: [PATCH RFC 1/2] PM / devfreq: Generic CPU frequency to device frequency mapping governor

[Hsin-Yi Wang]

Thanks!

On Thu, Jun 20, 2019 at 5:41 PM Sibi Sankar <sibis@xxxxxxxxxxxxxx> wrote:
>
> Hey Hsin-Yi, Chanwoo
>
> On 2019-06-20 15:02, Hsin-Yi Wang wrote:
> > Hi Chanwoo Choi, Saravana Kannan and Sibi Sankar,
> >
> > I've also tested Sibi Sankar's patch[1] locally with mt8183-cci, and
> > it works fine too!
> > It'd be great if Sibi Sankar or anyone who is familiar with the
> > original design can finish this implementation. But if no one has time
> > to do that, I think I can also help on address the comments. Thanks!
>
> Now that we have a user :) I am happy
> to repost the patch with the comments
> addressed.
>
> https://lkml.org/lkml/2019/6/14/4
> Also with ^^ patch and few more in the
> series the dt parsing of required-opps
> should get further simplified.
>
> >
> >
> > [1]
> > [RFC,2/9] OPP: Export a number of helpers to prevent code duplication
> > - https://patchwork.kernel.org/patch/10875199/
> > [RFC,3/9] PM / devfreq: Add cpu based scaling support to
> > passive_governor
> > - https://patchwork.kernel.org/patch/10875195/
> >
> > Hsin-Yi
> >
> > On Thu, Jun 20, 2019 at 2:56 PM Chanwoo Choi <cw00.choi@xxxxxxxxxxx>
> > wrote:
> >>
> >> + Sibi Sankar
> >>
> >> Hi, Hsin-Yi Wang, Saravana Kannan and Sibi Sankar
> >>
> >> I summarized the history of the related patch about this title.
> >>
> >> Firstly,
> >> As I knew, Saravana sent the patch[1] which contains
> >> 'governor_cpufreq_map.c' last year. According to the Myungoo's
> >> comment,
> >>
> >> Secondly,
> >> Sibi Sankar modified the 'governor_passive.c'[2] in order to support
> >> the mapping between cpu frequency and device frequency.
> >> Unfortunately, Sibi Sankar stopped the development about this
> >> because he had found the other method to get his purpose as I knew.
> >>
> >> Thirdly,
> >> Hsin-Yi Wang send the original patch of Saravana without modification.
> >>
> >>
> >> Sincerely, I think that the mapping between cpu frequency and device
> >> frequency is necessary. And I prefer the Sibi's approach which
> >> implements
> >> stuff to the existing 'passive' governor.
> >>
> >> We need to discuss about how to implement them by whom.
> >>
> >>
> >> [1] [v3,1/2] PM / devfreq: Generic CPU frequency to device frequency
> >> mapping governor
> >> - https://patchwork.kernel.org/patch/10553171/
> >>
> >> [2]
> >> [PATCH RFC 0/9] Add CPU based scaling support to Passive governor
> >> -
> >> https://lore.kernel.org/lkml/08c3cff8c39e3d82e044db93e992da72@xxxxxxxxxxxxxx/T/
> >> [PATCH RFC 3/9] PM / devfreq: Add cpu based scaling support to
> >> passive_governor
> >> -
> >> https://lore.kernel.org/lkml/08c3cff8c39e3d82e044db93e992da72@xxxxxxxxxxxxxx/T/#m1cafb7baf687d2a680d39c85d3ec7d1b590b68fc
> >>
> >>
> >> Best Regards,
> >> Chanwoo Choi
> >>
> >> On 19. 6. 18. ìí 1:14, Hsin-Yi Wang wrote:
> >> > From: Saravana Kannan <skannan@xxxxxxxxxxxxxx>
> >> >
> >> > From: Saravana Kannan <skannan@xxxxxxxxxxxxxx>
> >> >
> >> > Many CPU architectures have caches that can scale independent of the CPUs.
> >> > Frequency scaling of the caches is necessary to make sure the cache is not
> >> > a performance bottleneck that leads to poor performance and power. The same
> >> > idea applies for RAM/DDR.
> >> >
> >> > To achieve this, this patch adds a generic devfreq governor that takes the
> >> > current frequency of each CPU frequency domain and then adjusts the
> >> > frequency of the cache (or any devfreq device) based on the frequency of
> >> > the CPUs. It listens to CPU frequency transition notifiers to keep itself
> >> > up to date on the current CPU frequency.
> >> >
> >> > To decide the frequency of the device, the governor does one of the
> >> > following:
> >> >
> >> > * Uses a CPU frequency to device frequency mapping table
> >> >   - Either one mapping table used for all CPU freq policies (typically used
> >> >     for system with homogeneous cores/clusters that have the same OPPs).
> >> >   - One mapping table per CPU freq policy (typically used for ASMP systems
> >> >     with heterogeneous CPUs with different OPPs)
> >> >
> >> > OR
> >> >
> >> > * Scales the device frequency in proportion to the CPU frequency. So, if
> >> >   the CPUs are running at their max frequency, the device runs at its max
> >> >   frequency.  If the CPUs are running at their min frequency, the device
> >> >   runs at its min frequency. And interpolated for frequencies in between.
> >> >
> >> > Signed-off-by: Saravana Kannan <skannan@xxxxxxxxxxxxxx>
> >> > Signed-off-by: Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx>
> >> > ---
> >> >  .../bindings/devfreq/devfreq-cpufreq-map.txt  |  53 ++
> >> >  drivers/devfreq/Kconfig                       |   8 +
> >> >  drivers/devfreq/Makefile                      |   1 +
> >> >  drivers/devfreq/governor_cpufreq_map.c        | 583 ++++++++++++++++++
> >> >  4 files changed, 645 insertions(+)
> >> >  create mode 100644 Documentation/devicetree/bindings/devfreq/devfreq-cpufreq-map.txt
> >> >  create mode 100644 drivers/devfreq/governor_cpufreq_map.c
> >> >
> >> > diff --git a/Documentation/devicetree/bindings/devfreq/devfreq-cpufreq-map.txt b/Documentation/devicetree/bindings/devfreq/devfreq-cpufreq-map.txt
> >> > new file mode 100644
> >> > index 000000000000..982a30bcfc86
> >> > --- /dev/null
> >> > +++ b/Documentation/devicetree/bindings/devfreq/devfreq-cpufreq-map.txt
> >> > @@ -0,0 +1,53 @@
> >> > +Devfreq CPUfreq governor
> >> > +
> >> > +devfreq-cpufreq-map is a parent device that contains one or more child devices.
> >> > +Each child device provides CPU frequency to device frequency mapping for a
> >> > +specific device. Examples of devices that could use this are: DDR, cache and
> >> > +CCI.
> >> > +
> >> > +Parent device name shall be "devfreq-cpufreq-map".
> >> > +
> >> > +Required child device properties:
> >> > +- cpu-to-dev-map, or cpu-to-dev-map-<X>:
> >> > +                     A list of tuples where each tuple consists of a
> >> > +                     CPU frequency (KHz) and the corresponding device
> >> > +                     frequency. CPU frequencies not listed in the table
> >> > +                     will use the device frequency that corresponds to the
> >> > +                     next rounded up CPU frequency.
> >> > +                     Use "cpu-to-dev-map" if all CPUs in the system should
> >> > +                     share same mapping.
> >> > +                     Use cpu-to-dev-map-<cpuid> to describe different
> >> > +                     mappings for different CPUs. The property should be
> >> > +                     listed only for the first CPU if multiple CPUs are
> >> > +                     synchronous.
> >> > +- target-dev:                Phandle to device that this mapping applies to.
> >> > +
> >> > +Example:
> >> > +     devfreq-cpufreq-map {
> >> > +             cpubw-cpufreq {
> >> > +                     target-dev = <&cpubw>;
> >> > +                     cpu-to-dev-map =
> >> > +                             <  300000  1144000 >,
> >> > +                             <  422400  2288000 >,
> >> > +                             <  652800  3051000 >,
> >> > +                             <  883200  5996000 >,
> >> > +                             < 1190400  8056000 >,
> >> > +                             < 1497600 10101000 >,
> >> > +                             < 1728000 12145000 >,
> >> > +                             < 2649600 16250000 >;
> >> > +             };
> >> > +
> >> > +             cache-cpufreq {
> >> > +                     target-dev = <&cache>;
> >> > +                     cpu-to-dev-map =
> >> > +                             <  300000  300000 >,
> >> > +                             <  422400  422400 >,
> >> > +                             <  652800  499200 >,
> >> > +                             <  883200  576000 >,
> >> > +                             <  960000  960000 >,
> >> > +                             < 1497600 1036800 >,
> >> > +                             < 1574400 1574400 >,
> >> > +                             < 1728000 1651200 >,
> >> > +                             < 2649600 1728000 >;
> >> > +             };
> >> > +     };
> >> > diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
> >> > index 0c8204d6b78a..0303f5a400b6 100644
> >> > --- a/drivers/devfreq/Kconfig
> >> > +++ b/drivers/devfreq/Kconfig
> >> > @@ -74,6 +74,14 @@ config DEVFREQ_GOV_PASSIVE
> >> >         through sysfs entries. The passive governor recommends that
> >> >         devfreq device uses the OPP table to get the frequency/voltage.
> >> >
> >> > +config DEVFREQ_GOV_CPUFREQ_MAP
> >> > +     tristate "CPUfreq Map"
> >> > +     depends on CPU_FREQ
> >> > +     help
> >> > +       Chooses frequency based on the online CPUs' current frequency and a
> >> > +       CPU frequency to device frequency mapping table(s). This governor
> >> > +       can be useful for controlling devices such as DDR, cache, CCI, etc.
> >> > +
> >> >  comment "DEVFREQ Drivers"
> >> >
> >> >  config ARM_EXYNOS_BUS_DEVFREQ
> >> > diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
> >> > index 817dde779f16..81141e2c784f 100644
> >> > --- a/drivers/devfreq/Makefile
> >> > +++ b/drivers/devfreq/Makefile
> >> > @@ -6,6 +6,7 @@ obj-$(CONFIG_DEVFREQ_GOV_PERFORMANCE) += governor_performance.o
> >> >  obj-$(CONFIG_DEVFREQ_GOV_POWERSAVE)  += governor_powersave.o
> >> >  obj-$(CONFIG_DEVFREQ_GOV_USERSPACE)  += governor_userspace.o
> >> >  obj-$(CONFIG_DEVFREQ_GOV_PASSIVE)    += governor_passive.o
> >> > +obj-$(CONFIG_DEVFREQ_GOV_CPUFREQ_MAP)        += governor_cpufreq_map.o
> >> >
> >> >  # DEVFREQ Drivers
> >> >  obj-$(CONFIG_ARM_EXYNOS_BUS_DEVFREQ) += exynos-bus.o
> >> > diff --git a/drivers/devfreq/governor_cpufreq_map.c b/drivers/devfreq/governor_cpufreq_map.c
> >> > new file mode 100644
> >> > index 000000000000..084a3ffb8f54
> >> > --- /dev/null
> >> > +++ b/drivers/devfreq/governor_cpufreq_map.c
> >> > @@ -0,0 +1,583 @@
> >> > +// SPDX-License-Identifier: GPL-2.0
> >> > +/*
> >> > + * Copyright (c) 2014-2015, 2018, The Linux Foundation. All rights reserved.
> >> > + */
> >> > +
> >> > +#define pr_fmt(fmt) "dev-cpufreq-map: " fmt
> >> > +
> >> > +#include <linux/devfreq.h>
> >> > +#include <linux/cpu.h>
> >> > +#include <linux/cpufreq.h>
> >> > +#include <linux/cpumask.h>
> >> > +#include <linux/slab.h>
> >> > +#include <linux/platform_device.h>
> >> > +#include <linux/of.h>
> >> > +#include <linux/module.h>
> >> > +#include "governor.h"
> >> > +
> >> > +struct cpu_state {
> >> > +     unsigned int freq;
> >> > +     unsigned int min_freq;
> >> > +     unsigned int max_freq;
> >> > +     unsigned int first_cpu;
> >> > +};
> >> > +static struct cpu_state *state[NR_CPUS];
> >> > +static int cpufreq_cnt;
> >> > +
> >> > +struct freq_map {
> >> > +     unsigned int cpu_khz;
> >> > +     unsigned int target_freq;
> >> > +};
> >> > +
> >> > +struct devfreq_node {
> >> > +     struct devfreq *df;
> >> > +     void *orig_data;
> >> > +     struct device *dev;
> >> > +     struct device_node *of_node;
> >> > +     struct list_head list;
> >> > +     struct freq_map **map;
> >> > +     struct freq_map *common_map;
> >> > +};
> >> > +static LIST_HEAD(devfreq_list);
> >> > +static DEFINE_MUTEX(state_lock);
> >> > +static DEFINE_MUTEX(cpufreq_reg_lock);
> >> > +
> >> > +static void update_all_devfreqs(void)
> >> > +{
> >> > +     struct devfreq_node *node;
> >> > +
> >> > +     list_for_each_entry(node, &devfreq_list, list) {
> >> > +             struct devfreq *df = node->df;
> >> > +
> >> > +             if (!node->df)
> >> > +                     continue;
> >> > +             mutex_lock(&df->lock);
> >> > +             update_devfreq(df);
> >> > +             mutex_unlock(&df->lock);
> >> > +
> >> > +     }
> >> > +}
> >> > +
> >> > +static struct devfreq_node *find_devfreq_node(struct device *dev)
> >> > +{
> >> > +     struct devfreq_node *node;
> >> > +
> >> > +     list_for_each_entry(node, &devfreq_list, list)
> >> > +             if (node->dev == dev || node->of_node == dev->of_node)
> >> > +                     return node;
> >> > +
> >> > +     return NULL;
> >> > +}
> >> > +
> >> > +/* ==================== cpufreq part ==================== */
> >> > +static struct cpu_state *add_policy(struct cpufreq_policy *policy)
> >> > +{
> >> > +     struct cpu_state *new_state;
> >> > +     unsigned int cpu, first_cpu;
> >> > +
> >> > +     new_state = kzalloc(sizeof(struct cpu_state), GFP_KERNEL);
> >> > +     if (!new_state)
> >> > +             return NULL;
> >> > +
> >> > +     first_cpu = cpumask_first(policy->related_cpus);
> >> > +     new_state->first_cpu = first_cpu;
> >> > +     new_state->freq = policy->cur;
> >> > +     new_state->min_freq = policy->cpuinfo.min_freq;
> >> > +     new_state->max_freq = policy->cpuinfo.max_freq;
> >> > +
> >> > +     for_each_cpu(cpu, policy->related_cpus)
> >> > +             state[cpu] = new_state;
> >> > +
> >> > +     return new_state;
> >> > +}
> >> > +
> >> > +static int cpufreq_trans_notifier(struct notifier_block *nb,
> >> > +             unsigned long event, void *data)
> >> > +{
> >> > +     struct cpufreq_freqs *freq = data;
> >> > +     struct cpu_state *s;
> >> > +     struct cpufreq_policy *policy = NULL;
> >> > +
> >> > +     if (event != CPUFREQ_POSTCHANGE)
> >> > +             return 0;
> >> > +
> >> > +     mutex_lock(&state_lock);
> >> > +
> >> > +     s = state[freq->cpu];
> >> > +     if (!s) {
> >> > +             policy = cpufreq_cpu_get(freq->cpu);
> >> > +             if (policy) {
> >> > +                     s = add_policy(policy);
> >> > +                     cpufreq_cpu_put(policy);
> >> > +             }
> >> > +     }
> >> > +     if (!s)
> >> > +             goto out;
> >> > +
> >> > +     if (s->freq != freq->new || policy) {
> >> > +             s->freq = freq->new;
> >> > +             update_all_devfreqs();
> >> > +     }
> >> > +
> >> > +out:
> >> > +     mutex_unlock(&state_lock);
> >> > +     return 0;
> >> > +}
> >> > +
> >> > +static struct notifier_block cpufreq_trans_nb = {
> >> > +     .notifier_call = cpufreq_trans_notifier
> >> > +};
> >> > +
> >> > +static int register_cpufreq(void)
> >> > +{
> >> > +     int ret = 0;
> >> > +     unsigned int cpu;
> >> > +     struct cpufreq_policy *policy;
> >> > +
> >> > +     mutex_lock(&cpufreq_reg_lock);
> >> > +
> >> > +     if (cpufreq_cnt)
> >> > +             goto cnt_not_zero;
> >> > +
> >> > +     get_online_cpus();
> >> > +     ret = cpufreq_register_notifier(&cpufreq_trans_nb,
> >> > +                             CPUFREQ_TRANSITION_NOTIFIER);
> >> > +     if (ret)
> >> > +             goto out;
> >> > +
> >> > +     for_each_online_cpu(cpu) {
> >> > +             policy = cpufreq_cpu_get(cpu);
> >> > +             if (policy) {
> >> > +                     add_policy(policy);
> >> > +                     cpufreq_cpu_put(policy);
> >> > +             }
> >> > +     }
> >> > +out:
> >> > +     put_online_cpus();
> >> > +cnt_not_zero:
> >> > +     if (!ret)
> >> > +             cpufreq_cnt++;
> >> > +     mutex_unlock(&cpufreq_reg_lock);
> >> > +     return ret;
> >> > +}
> >> > +
> >> > +static int unregister_cpufreq(void)
> >> > +{
> >> > +     int ret = 0;
> >> > +     int cpu;
> >> > +
> >> > +     mutex_lock(&cpufreq_reg_lock);
> >> > +
> >> > +     if (cpufreq_cnt > 1)
> >> > +             goto out;
> >> > +
> >> > +     cpufreq_unregister_notifier(&cpufreq_trans_nb,
> >> > +                             CPUFREQ_TRANSITION_NOTIFIER);
> >> > +
> >> > +     for (cpu = ARRAY_SIZE(state) - 1; cpu >= 0; cpu--) {
> >> > +             if (!state[cpu])
> >> > +                     continue;
> >> > +             if (state[cpu]->first_cpu == cpu)
> >> > +                     kfree(state[cpu]);
> >> > +             state[cpu] = NULL;
> >> > +     }
> >> > +
> >> > +out:
> >> > +     cpufreq_cnt--;
> >> > +     mutex_unlock(&cpufreq_reg_lock);
> >> > +     return ret;
> >> > +}
> >> > +
> >> > +/* ==================== devfreq part ==================== */
> >> > +
> >> > +static unsigned int interpolate_freq(struct devfreq *df, unsigned int cpu)
> >> > +{
> >> > +     unsigned long *freq_table = df->profile->freq_table;
> >> > +     unsigned int cpu_min = state[cpu]->min_freq;
> >> > +     unsigned int cpu_max = state[cpu]->max_freq;
> >> > +     unsigned int cpu_freq = state[cpu]->freq;
> >> > +     unsigned int dev_min, dev_max, cpu_percent;
> >> > +
> >> > +     if (freq_table) {
> >> > +             dev_min = freq_table[0];
> >> > +             dev_max = freq_table[df->profile->max_state - 1];
> >> > +     } else {
> >> > +             if (df->max_freq <= df->min_freq)
> >> > +                     return 0;
> >> > +             dev_min = df->min_freq;
> >> > +             dev_max = df->max_freq;
> >> > +     }
> >> > +
> >> > +     cpu_percent = ((cpu_freq - cpu_min) * 100) / (cpu_max - cpu_min);
> >> > +     return dev_min + mult_frac(dev_max - dev_min, cpu_percent, 100);
> >> > +}
> >> > +
> >> > +static unsigned int cpu_to_dev_freq(struct devfreq *df, unsigned int cpu)
> >> > +{
> >> > +     struct freq_map *map = NULL;
> >> > +     unsigned int cpu_khz = 0, freq;
> >> > +     struct devfreq_node *n = df->data;
> >> > +
> >> > +     if (!state[cpu] || state[cpu]->first_cpu != cpu) {
> >> > +             freq = 0;
> >> > +             goto out;
> >> > +     }
> >> > +
> >> > +     if (n->common_map)
> >> > +             map = n->common_map;
> >> > +     else if (n->map)
> >> > +             map = n->map[cpu];
> >> > +
> >> > +     cpu_khz = state[cpu]->freq;
> >> > +
> >> > +     if (!map) {
> >> > +             freq = interpolate_freq(df, cpu);
> >> > +             goto out;
> >> > +     }
> >> > +
> >> > +     while (map->cpu_khz && map->cpu_khz < cpu_khz)
> >> > +             map++;
> >> > +     if (!map->cpu_khz)
> >> > +             map--;
> >> > +     freq = map->target_freq;
> >> > +
> >> > +out:
> >> > +     dev_dbg(df->dev.parent, "CPU%u: %d -> dev: %u\n", cpu, cpu_khz, freq);
> >> > +     return freq;
> >> > +}
> >> > +
> >> > +static int devfreq_cpufreq_get_freq(struct devfreq *df,
> >> > +                                     unsigned long *freq)
> >> > +{
> >> > +     unsigned int cpu, tgt_freq = 0;
> >> > +     struct devfreq_node *node;
> >> > +
> >> > +     node = df->data;
> >> > +     if (!node) {
> >> > +             pr_err("Unable to find devfreq node!\n");
> >> > +             return -ENODEV;
> >> > +     }
> >> > +
> >> > +     for_each_possible_cpu(cpu)
> >> > +             tgt_freq = max(tgt_freq, cpu_to_dev_freq(df, cpu));
> >> > +
> >> > +     *freq = tgt_freq;
> >> > +     return 0;
> >> > +}
> >> > +
> >> > +static unsigned int show_table(char *buf, unsigned int len,
> >> > +                             struct freq_map *map)
> >> > +{
> >> > +     unsigned int cnt = 0;
> >> > +
> >> > +     cnt += snprintf(buf + cnt, len - cnt, "CPU freq\tDevice freq\n");
> >> > +
> >> > +     while (map->cpu_khz && cnt < len) {
> >> > +             cnt += snprintf(buf + cnt, len - cnt, "%8u\t%11u\n",
> >> > +                             map->cpu_khz, map->target_freq);
> >> > +             map++;
> >> > +     }
> >> > +     if (cnt < len)
> >> > +             cnt += snprintf(buf + cnt, len - cnt, "\n");
> >> > +
> >> > +     return cnt;
> >> > +}
> >> > +
> >> > +static ssize_t freq_map_show(struct device *dev, struct device_attribute *attr,
> >> > +                     char *buf)
> >> > +{
> >> > +     struct devfreq *df = to_devfreq(dev);
> >> > +     struct devfreq_node *n = df->data;
> >> > +     struct freq_map *map;
> >> > +     unsigned int cnt = 0, cpu;
> >> > +
> >> > +     mutex_lock(&state_lock);
> >> > +     if (n->common_map) {
> >> > +             map = n->common_map;
> >> > +             cnt += snprintf(buf + cnt, PAGE_SIZE - cnt,
> >> > +                             "Common table for all CPUs:\n");
> >> > +             cnt += show_table(buf + cnt, PAGE_SIZE - cnt, map);
> >> > +     } else if (n->map) {
> >> > +             for_each_possible_cpu(cpu) {
> >> > +                     map = n->map[cpu];
> >> > +                     if (!map)
> >> > +                             continue;
> >> > +                     cnt += snprintf(buf + cnt, PAGE_SIZE - cnt,
> >> > +                                     "CPU %u:\n", cpu);
> >> > +                     if (cnt >= PAGE_SIZE)
> >> > +                             break;
> >> > +                     cnt += show_table(buf + cnt, PAGE_SIZE - cnt, map);
> >> > +                     if (cnt >= PAGE_SIZE)
> >> > +                             break;
> >> > +             }
> >> > +     } else {
> >> > +             cnt += snprintf(buf + cnt, PAGE_SIZE - cnt,
> >> > +                             "Device freq interpolated based on CPU freq\n");
> >> > +     }
> >> > +     mutex_unlock(&state_lock);
> >> > +
> >> > +     return cnt;
> >> > +}
> >> > +
> >> > +static DEVICE_ATTR_RO(freq_map);
> >> > +static struct attribute *dev_attr[] = {
> >> > +     &dev_attr_freq_map.attr,
> >> > +     NULL,
> >> > +};
> >> > +
> >> > +static struct attribute_group dev_attr_group = {
> >> > +     .name = "cpufreq-map",
> >> > +     .attrs = dev_attr,
> >> > +};
> >> > +
> >> > +static int devfreq_cpufreq_gov_start(struct devfreq *devfreq)
> >> > +{
> >> > +     int ret = 0;
> >> > +     struct devfreq_node *node;
> >> > +     bool alloc = false;
> >> > +
> >> > +     ret = register_cpufreq();
> >> > +     if (ret)
> >> > +             return ret;
> >> > +
> >> > +     ret = sysfs_create_group(&devfreq->dev.kobj, &dev_attr_group);
> >> > +     if (ret) {
> >> > +             unregister_cpufreq();
> >> > +             return ret;
> >> > +     }
> >> > +
> >> > +     mutex_lock(&state_lock);
> >> > +
> >> > +     node = find_devfreq_node(devfreq->dev.parent);
> >> > +     if (node == NULL) {
> >> > +             node = kzalloc(sizeof(struct devfreq_node), GFP_KERNEL);
> >> > +             if (!node) {
> >> > +                     ret = -ENOMEM;
> >> > +                     goto alloc_fail;
> >> > +             }
> >> > +             alloc = true;
> >> > +             node->dev = devfreq->dev.parent;
> >> > +             list_add_tail(&node->list, &devfreq_list);
> >> > +     }
> >> > +     node->df = devfreq;
> >> > +     node->orig_data = devfreq->data;
> >> > +     devfreq->data = node;
> >> > +
> >> > +     mutex_lock(&devfreq->lock);
> >> > +     ret = update_devfreq(devfreq);
> >> > +     mutex_unlock(&devfreq->lock);
> >> > +     if (ret) {
> >> > +             pr_err("Freq update failed!\n");
> >> > +             goto update_fail;
> >> > +     }
> >> > +
> >> > +     mutex_unlock(&state_lock);
> >> > +     return 0;
> >> > +
> >> > +update_fail:
> >> > +     devfreq->data = node->orig_data;
> >> > +     if (alloc) {
> >> > +             list_del(&node->list);
> >> > +             kfree(node);
> >> > +     }
> >> > +alloc_fail:
> >> > +     mutex_unlock(&state_lock);
> >> > +     sysfs_remove_group(&devfreq->dev.kobj, &dev_attr_group);
> >> > +     unregister_cpufreq();
> >> > +     return ret;
> >> > +}
> >> > +
> >> > +static void devfreq_cpufreq_gov_stop(struct devfreq *devfreq)
> >> > +{
> >> > +     struct devfreq_node *node = devfreq->data;
> >> > +
> >> > +     mutex_lock(&state_lock);
> >> > +     devfreq->data = node->orig_data;
> >> > +     if (node->map || node->common_map) {
> >> > +             node->df = NULL;
> >> > +     } else {
> >> > +             list_del(&node->list);
> >> > +             kfree(node);
> >> > +     }
> >> > +     mutex_unlock(&state_lock);
> >> > +
> >> > +     sysfs_remove_group(&devfreq->dev.kobj, &dev_attr_group);
> >> > +     unregister_cpufreq();
> >> > +}
> >> > +
> >> > +static int devfreq_cpufreq_ev_handler(struct devfreq *devfreq,
> >> > +                                     unsigned int event, void *data)
> >> > +{
> >> > +     int ret;
> >> > +
> >> > +     switch (event) {
> >> > +     case DEVFREQ_GOV_START:
> >> > +
> >> > +             ret = devfreq_cpufreq_gov_start(devfreq);
> >> > +             if (ret) {
> >> > +                     pr_err("Governor start failed!\n");
> >> > +                     return ret;
> >> > +             }
> >> > +             pr_debug("Enabled CPUfreq-map governor\n");
> >> > +             break;
> >> > +
> >> > +     case DEVFREQ_GOV_STOP:
> >> > +
> >> > +             devfreq_cpufreq_gov_stop(devfreq);
> >> > +             pr_debug("Disabled dev CPUfreq-map governor\n");
> >> > +             break;
> >> > +     }
> >> > +
> >> > +     return 0;
> >> > +}
> >> > +
> >> > +static struct devfreq_governor devfreq_cpufreq = {
> >> > +     .name = "cpufreq-map",
> >> > +     .get_target_freq = devfreq_cpufreq_get_freq,
> >> > +     .event_handler = devfreq_cpufreq_ev_handler,
> >> > +};
> >> > +
> >> > +#define NUM_COLS     2
> >> > +static struct freq_map *read_tbl(struct device_node *of_node, char *prop_name)
> >> > +{
> >> > +     int len, nf, i, j;
> >> > +     u32 data;
> >> > +     struct freq_map *tbl;
> >> > +
> >> > +     if (!of_find_property(of_node, prop_name, &len))
> >> > +             return NULL;
> >> > +     len /= sizeof(data);
> >> > +
> >> > +     if (len % NUM_COLS || len == 0)
> >> > +             return NULL;
> >> > +     nf = len / NUM_COLS;
> >> > +
> >> > +     tbl = kzalloc((nf + 1) * sizeof(*tbl), GFP_KERNEL);
> >> > +     if (!tbl)
> >> > +             return NULL;
> >> > +
> >> > +     for (i = 0, j = 0; i < nf; i++, j += 2) {
> >> > +             of_property_read_u32_index(of_node, prop_name, j, &data);
> >> > +             tbl[i].cpu_khz = data;
> >> > +
> >> > +             of_property_read_u32_index(of_node, prop_name, j + 1, &data);
> >> > +             tbl[i].target_freq = data;
> >> > +     }
> >> > +     tbl[i].cpu_khz = 0;
> >> > +
> >> > +     return tbl;
> >> > +}
> >> > +
> >> > +#define PROP_TARGET "target-dev"
> >> > +#define PROP_TABLE "cpu-to-dev-map"
> >> > +static int add_table_from_of(struct device_node *of_node)
> >> > +{
> >> > +     struct device_node *target_of_node;
> >> > +     struct devfreq_node *node;
> >> > +     struct freq_map *common_tbl;
> >> > +     struct freq_map **tbl_list = NULL;
> >> > +     static char prop_name[] = PROP_TABLE "-999999";
> >> > +     int cpu, ret, cnt = 0, prop_sz = ARRAY_SIZE(prop_name);
> >> > +
> >> > +     target_of_node = of_parse_phandle(of_node, PROP_TARGET, 0);
> >> > +     if (!target_of_node)
> >> > +             return -EINVAL;
> >> > +
> >> > +     node = kzalloc(sizeof(struct devfreq_node), GFP_KERNEL);
> >> > +     if (!node)
> >> > +             return -ENOMEM;
> >> > +
> >> > +     common_tbl = read_tbl(of_node, PROP_TABLE);
> >> > +     if (!common_tbl) {
> >> > +             tbl_list = kzalloc(sizeof(*tbl_list) * NR_CPUS, GFP_KERNEL);
> >> > +             if (!tbl_list) {
> >> > +                     ret = -ENOMEM;
> >> > +                     goto err_list;
> >> > +             }
> >> > +
> >> > +             for_each_possible_cpu(cpu) {
> >> > +                     ret = snprintf(prop_name, prop_sz, "%s-%d",
> >> > +                                     PROP_TABLE, cpu);
> >> > +                     if (ret >= prop_sz) {
> >> > +                             pr_warn("More CPUs than I can handle!\n");
> >> > +                             pr_warn("Skipping rest of the tables!\n");
> >> > +                             break;
> >> > +                     }
> >> > +                     tbl_list[cpu] = read_tbl(of_node, prop_name);
> >> > +                     if (tbl_list[cpu])
> >> > +                             cnt++;
> >> > +             }
> >> > +     }
> >> > +     if (!common_tbl && !cnt) {
> >> > +             ret = -EINVAL;
> >> > +             goto err_tbl;
> >> > +     }
> >> > +
> >> > +     mutex_lock(&state_lock);
> >> > +     node->of_node = target_of_node;
> >> > +     node->map = tbl_list;
> >> > +     node->common_map = common_tbl;
> >> > +     list_add_tail(&node->list, &devfreq_list);
> >> > +     mutex_unlock(&state_lock);
> >> > +
> >> > +     return 0;
> >> > +err_tbl:
> >> > +     kfree(tbl_list);
> >> > +err_list:
> >> > +     kfree(node);
> >> > +     return ret;
> >> > +}
> >> > +
> >> > +static int __init devfreq_cpufreq_init(void)
> >> > +{
> >> > +     int ret;
> >> > +     struct device_node *of_par, *of_child;
> >> > +
> >> > +     of_par = of_find_node_by_name(NULL, "devfreq-cpufreq-map");
> >> > +     if (of_par) {
> >> > +             for_each_child_of_node(of_par, of_child) {
> >> > +                     ret = add_table_from_of(of_child);
> >> > +                     if (ret)
> >> > +                             pr_err("Parsing %s failed!\n", of_child->name);
> >> > +                     else
> >> > +                             pr_debug("Parsed %s.\n", of_child->name);
> >> > +             }
> >> > +             of_node_put(of_par);
> >> > +     } else {
> >> > +             pr_info("No tables parsed from DT.\n");
> >> > +     }
> >> > +
> >> > +     ret = devfreq_add_governor(&devfreq_cpufreq);
> >> > +     if (ret) {
> >> > +             pr_err("cpufreq-map governor add failed!\n");
> >> > +             return ret;
> >> > +     }
> >> > +
> >> > +     return 0;
> >> > +}
> >> > +subsys_initcall(devfreq_cpufreq_init);
> >> > +
> >> > +static void __exit devfreq_cpufreq_exit(void)
> >> > +{
> >> > +     int ret, cpu;
> >> > +     struct devfreq_node *node, *tmp;
> >> > +
> >> > +     ret = devfreq_remove_governor(&devfreq_cpufreq);
> >> > +     if (ret)
> >> > +             pr_err("cpufreq-map governor remove failed!\n");
> >> > +
> >> > +     mutex_lock(&state_lock);
> >> > +     list_for_each_entry_safe(node, tmp, &devfreq_list, list) {
> >> > +             kfree(node->common_map);
> >> > +             for_each_possible_cpu(cpu)
> >> > +                     kfree(node->map[cpu]);
> >> > +             kfree(node->map);
> >> > +             list_del(&node->list);
> >> > +             kfree(node);
> >> > +     }
> >> > +     mutex_unlock(&state_lock);
> >> > +}
> >> > +module_exit(devfreq_cpufreq_exit);
> >> > +
> >> > +MODULE_DESCRIPTION("devfreq gov that sets dev freq based on current CPU freq");
> >> > +MODULE_LICENSE("GPL v2");
> >> >
>
> --
> -- Sibi Sankar --
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> a Linux Foundation Collaborative Project.