Re: [PATCH v2 1/3] powercap: arm_scmi: Add SCMI Powercap based driver

[Rafael J. Wysocki]

On Tue, Sep 6, 2022 at 4:24 PM Cristian Marussi
<cristian.marussi@xxxxxxx> wrote:
>
> Add a powercap driver that, using the ARM SCMI Protocol to query the SCMI
> platform firmware for the list of existing Powercap domains, registers all
> of such discovered domains under the new 'arm-scmi' powercap control type.
>
> A new simple powercap zone and constraint is registered for all the SCMI
> powercap zones that are found.
>
> Cc: Rafael J. Wysocki <rafael@xxxxxxxxxx>
> Cc: linux-pm@xxxxxxxxxxxxxxx
> Signed-off-by: Cristian Marussi <cristian.marussi@xxxxxxx>

Can you please fold patches [2-3/3] in the series into the first one?
You can add information that fixes from Dan Carpenter are included to
the patch changelog.

Also I would like the SCMI people to look at this and tell me that it
makes sense to them.

> ---
> v1 --> v2
> - using clamp_t() to simplify normalizations
> - cleanup style in block of var declarations
> - refactor scale conversions code
> - add MAINTAINER entry
> - refactored normalizations and added dev_dbg
> vOLD --> v1
> - fix _init cleaning up powerctrl zone on failure
> - removed uneeded casting
> - simplified normalization helpers
> ---
>  MAINTAINERS                          |   1 +
>  drivers/powercap/Kconfig             |  13 +
>  drivers/powercap/Makefile            |   1 +
>  drivers/powercap/arm_scmi_powercap.c | 508 +++++++++++++++++++++++++++
>  4 files changed, 523 insertions(+)
>  create mode 100644 drivers/powercap/arm_scmi_powercap.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 9d7f64dc0efe..c3bfc7c5aa91 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -19737,6 +19737,7 @@ F:      drivers/clk/clk-sc[mp]i.c
>  F:     drivers/cpufreq/sc[mp]i-cpufreq.c
>  F:     drivers/firmware/arm_scmi/
>  F:     drivers/firmware/arm_scpi.c
> +F:     drivers/powercap/arm_scmi_powercap.c
>  F:     drivers/regulator/scmi-regulator.c
>  F:     drivers/reset/reset-scmi.c
>  F:     include/linux/sc[mp]i_protocol.h
> diff --git a/drivers/powercap/Kconfig b/drivers/powercap/Kconfig
> index 515e3ceb3393..90d33cd1b670 100644
> --- a/drivers/powercap/Kconfig
> +++ b/drivers/powercap/Kconfig
> @@ -44,6 +44,19 @@ config IDLE_INJECT
>           synchronously on a set of specified CPUs or alternatively
>           on a per CPU basis.
>
> +config ARM_SCMI_POWERCAP
> +       tristate "ARM SCMI Powercap driver"
> +       depends on ARM_SCMI_PROTOCOL
> +       help
> +         This enables support for the ARM Powercap based on ARM SCMI
> +         Powercap protocol.
> +
> +         ARM SCMI Powercap protocol allows power limits to be enforced
> +         and monitored against the SCMI Powercap domains advertised as
> +         available by the SCMI platform firmware.
> +
> +         When compiled as module it will be called arm_scmi_powercap.ko.
> +
>  config DTPM
>         bool "Power capping for Dynamic Thermal Power Management (EXPERIMENTAL)"
>         depends on OF
> diff --git a/drivers/powercap/Makefile b/drivers/powercap/Makefile
> index 494617cdad88..4474201b4aa7 100644
> --- a/drivers/powercap/Makefile
> +++ b/drivers/powercap/Makefile
> @@ -6,3 +6,4 @@ obj-$(CONFIG_POWERCAP)  += powercap_sys.o
>  obj-$(CONFIG_INTEL_RAPL_CORE) += intel_rapl_common.o
>  obj-$(CONFIG_INTEL_RAPL) += intel_rapl_msr.o
>  obj-$(CONFIG_IDLE_INJECT) += idle_inject.o
> +obj-$(CONFIG_ARM_SCMI_POWERCAP) += arm_scmi_powercap.o
> diff --git a/drivers/powercap/arm_scmi_powercap.c b/drivers/powercap/arm_scmi_powercap.c
> new file mode 100644
> index 000000000000..a91438867f8c
> --- /dev/null
> +++ b/drivers/powercap/arm_scmi_powercap.c
> @@ -0,0 +1,508 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * SCMI Powercap support.
> + *
> + * Copyright (C) 2022 ARM Ltd.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/math.h>
> +#include <linux/limits.h>
> +#include <linux/list.h>
> +#include <linux/module.h>
> +#include <linux/powercap.h>
> +#include <linux/scmi_protocol.h>
> +
> +#define to_scmi_powercap_zone(z)               \
> +       container_of(z, struct scmi_powercap_zone, zone)
> +
> +static const struct scmi_powercap_proto_ops *powercap_ops;
> +
> +struct scmi_powercap_zone {
> +       unsigned int height;
> +       struct device *dev;
> +       struct scmi_protocol_handle *ph;
> +       const struct scmi_powercap_info *info;
> +       struct scmi_powercap_zone *spzones;
> +       struct powercap_zone zone;
> +       struct list_head node;
> +};
> +
> +struct scmi_powercap_root {
> +       unsigned int num_zones;
> +       struct scmi_powercap_zone *spzones;
> +       struct list_head *registered_zones;
> +};
> +
> +static struct powercap_control_type *scmi_top_pcntrl;
> +
> +static int scmi_powercap_zone_release(struct powercap_zone *pz)
> +{
> +       return 0;
> +}
> +
> +static int scmi_powercap_get_max_power_range_uw(struct powercap_zone *pz,
> +                                               u64 *max_power_range_uw)
> +{
> +       *max_power_range_uw = U32_MAX;
> +       return 0;
> +}
> +
> +static int scmi_powercap_get_power_uw(struct powercap_zone *pz,
> +                                     u64 *power_uw)
> +{
> +       struct scmi_powercap_zone *spz = to_scmi_powercap_zone(pz);
> +       u32 avg_power, pai;
> +       int ret;
> +
> +       if (!spz->info->powercap_monitoring)
> +               return -EINVAL;
> +
> +       ret = powercap_ops->measurements_get(spz->ph, spz->info->id, &avg_power,
> +                                            &pai);
> +       if (ret)
> +               return ret;
> +
> +       *power_uw = avg_power;
> +       if (spz->info->powercap_scale_mw)
> +               *power_uw *= 1000;
> +
> +       return 0;
> +}
> +
> +static const struct powercap_zone_ops zone_ops = {
> +       .get_max_power_range_uw = scmi_powercap_get_max_power_range_uw,
> +       .get_power_uw = scmi_powercap_get_power_uw,
> +       .release = scmi_powercap_zone_release,
> +};
> +
> +static void scmi_powercap_normalize_cap(const struct scmi_powercap_zone *spz,
> +                                       u64 power_limit_uw, u32 *norm)
> +{
> +       bool scale_mw = spz->info->powercap_scale_mw;
> +       u64 val;
> +
> +       val = scale_mw ? DIV_ROUND_UP_ULL(power_limit_uw, 1000) : power_limit_uw;
> +       /*
> +        * This cast is lossless since here @req_power is certain to be within
> +        * the range [min_power_cap, max_power_cap] whose bounds are assured to
> +        * be two unsigned 32bits quantities.
> +        */
> +       *norm = clamp_t(u32, val, spz->info->min_power_cap,
> +                       spz->info->max_power_cap);
> +       *norm = rounddown(*norm, spz->info->power_cap_step);
> +
> +       val = (scale_mw) ? *norm * 1000 : *norm;
> +       if (power_limit_uw != val)
> +               dev_dbg(spz->dev,
> +                       "Normalized %s:CAP - requested:%llu - normalized:%llu\n",
> +                       spz->info->name, power_limit_uw, val);
> +}
> +
> +static int scmi_powercap_set_power_limit_uw(struct powercap_zone *pz, int cid,
> +                                           u64 power_uw)
> +{
> +       struct scmi_powercap_zone *spz = to_scmi_powercap_zone(pz);
> +       u32 norm_power;
> +
> +       if (!spz->info->powercap_cap_config)
> +               return -EINVAL;
> +
> +       scmi_powercap_normalize_cap(spz, power_uw, &norm_power);
> +
> +       return powercap_ops->cap_set(spz->ph, spz->info->id, norm_power, false);
> +}
> +
> +static int scmi_powercap_get_power_limit_uw(struct powercap_zone *pz, int cid,
> +                                           u64 *power_limit_uw)
> +{
> +       struct scmi_powercap_zone *spz = to_scmi_powercap_zone(pz);
> +       u32 power;
> +       int ret;
> +
> +       ret = powercap_ops->cap_get(spz->ph, spz->info->id, &power);
> +       if (ret)
> +               return ret;
> +
> +       *power_limit_uw = power;
> +       if (spz->info->powercap_scale_mw)
> +               *power_limit_uw *= 1000;
> +
> +       return 0;
> +}
> +
> +static void scmi_powercap_normalize_time(const struct scmi_powercap_zone *spz,
> +                                        u64 time_us, u32 *norm)
> +{
> +       /*
> +        * This cast is lossless since here @time_us is certain to be within the
> +        * range [min_pai, max_pai] whose bounds are assured to be two unsigned
> +        * 32bits quantities.
> +        */
> +       *norm = clamp_t(u32, time_us, spz->info->min_pai, spz->info->max_pai);
> +       *norm = rounddown(*norm, spz->info->pai_step);
> +
> +       if (time_us != *norm)
> +               dev_dbg(spz->dev,
> +                       "Normalized %s:PAI - requested:%llu - normalized:%u\n",
> +                       spz->info->name, time_us, *norm);
> +}
> +
> +static int scmi_powercap_set_time_window_us(struct powercap_zone *pz, int cid,
> +                                           u64 time_window_us)
> +{
> +       struct scmi_powercap_zone *spz = to_scmi_powercap_zone(pz);
> +       u32 norm_pai;
> +
> +       if (!spz->info->powercap_pai_config)
> +               return -EINVAL;
> +
> +       scmi_powercap_normalize_time(spz, time_window_us, &norm_pai);
> +
> +       return powercap_ops->pai_set(spz->ph, spz->info->id, norm_pai);
> +}
> +
> +static int scmi_powercap_get_time_window_us(struct powercap_zone *pz, int cid,
> +                                           u64 *time_window_us)
> +{
> +       struct scmi_powercap_zone *spz = to_scmi_powercap_zone(pz);
> +       int ret;
> +       u32 pai;
> +
> +       ret = powercap_ops->pai_get(spz->ph, spz->info->id, &pai);
> +       if (ret)
> +               return ret;
> +
> +       *time_window_us = pai;
> +
> +       return 0;
> +}
> +
> +static int scmi_powercap_get_max_power_uw(struct powercap_zone *pz, int cid,
> +                                         u64 *max_power_uw)
> +{
> +       struct scmi_powercap_zone *spz = to_scmi_powercap_zone(pz);
> +
> +       *max_power_uw = spz->info->max_power_cap;
> +       if (spz->info->powercap_scale_mw)
> +               *max_power_uw *= 1000;
> +
> +       return 0;
> +}
> +
> +static int scmi_powercap_get_min_power_uw(struct powercap_zone *pz, int cid,
> +                                         u64 *min_power_uw)
> +{
> +       struct scmi_powercap_zone *spz = to_scmi_powercap_zone(pz);
> +
> +       *min_power_uw = spz->info->min_power_cap;
> +       if (spz->info->powercap_scale_mw)
> +               *min_power_uw *= 1000;
> +
> +       return 0;
> +}
> +
> +static int scmi_powercap_get_max_time_window_us(struct powercap_zone *pz,
> +                                               int cid, u64 *time_window_us)
> +{
> +       struct scmi_powercap_zone *spz = to_scmi_powercap_zone(pz);
> +
> +       *time_window_us = spz->info->max_pai;
> +
> +       return 0;
> +}
> +
> +static int scmi_powercap_get_min_time_window_us(struct powercap_zone *pz,
> +                                               int cid, u64 *time_window_us)
> +{
> +       struct scmi_powercap_zone *spz = to_scmi_powercap_zone(pz);
> +
> +       *time_window_us = (u64)spz->info->min_pai;
> +
> +       return 0;
> +}
> +
> +static const char *scmi_powercap_get_name(struct powercap_zone *pz, int cid)
> +{
> +       return "SCMI power-cap";
> +}
> +
> +static const struct powercap_zone_constraint_ops constraint_ops  = {
> +       .set_power_limit_uw = scmi_powercap_set_power_limit_uw,
> +       .get_power_limit_uw = scmi_powercap_get_power_limit_uw,
> +       .set_time_window_us = scmi_powercap_set_time_window_us,
> +       .get_time_window_us = scmi_powercap_get_time_window_us,
> +       .get_max_power_uw = scmi_powercap_get_max_power_uw,
> +       .get_min_power_uw = scmi_powercap_get_min_power_uw,
> +       .get_max_time_window_us = scmi_powercap_get_max_time_window_us,
> +       .get_min_time_window_us = scmi_powercap_get_min_time_window_us,
> +       .get_name = scmi_powercap_get_name,
> +};
> +
> +static void scmi_powercap_unregister_all_zones(struct scmi_powercap_root *pr)
> +{
> +       int i;
> +
> +       /* Un-register children zones first starting from the leaves */
> +       for (i = pr->num_zones - 1; i >= 0; i--) {
> +               if (!list_empty(&pr->registered_zones[i])) {
> +                       struct scmi_powercap_zone *spz;
> +
> +                       list_for_each_entry(spz, &pr->registered_zones[i], node)
> +                               powercap_unregister_zone(scmi_top_pcntrl,
> +                                                        &spz->zone);
> +               }
> +       }
> +}
> +
> +static inline bool
> +scmi_powercap_is_zone_registered(struct scmi_powercap_zone *spz)
> +{
> +       return !list_empty(&spz->node);
> +}
> +
> +static inline unsigned int
> +scmi_powercap_get_zone_height(struct scmi_powercap_zone *spz)
> +{
> +       if (spz->info->parent_id == SCMI_POWERCAP_ROOT_ZONE_ID)
> +               return 0;
> +
> +       return spz->spzones[spz->info->parent_id].height + 1;
> +}
> +
> +static inline struct scmi_powercap_zone *
> +scmi_powercap_get_parent_zone(struct scmi_powercap_zone *spz)
> +{
> +       if (spz->info->parent_id == SCMI_POWERCAP_ROOT_ZONE_ID)
> +               return NULL;
> +
> +       return &spz->spzones[spz->info->parent_id];
> +}
> +
> +/**
> + * scmi_powercap_register_zone  - Register an SCMI powercap zone recursively
> + *
> + * @pr: A reference to the root powercap zones descriptors
> + * @spz: A reference to the SCMI powercap zone to register
> + *
> + * When registering SCMI powercap zones with the powercap framework we should
> + * take care to always register zones starting from the root ones and to
> + * deregister starting from the leaves.
> + *
> + * Unfortunately we cannot assume that the array of available SCMI powercap
> + * zones provided by the SCMI platform firmware is built to comply with such
> + * requirement.
> + *
> + * This function, given an SCMI powercap zone to register, takes care to walk
> + * the SCMI powercap zones tree up to the root looking recursively for
> + * unregistered parent zones before registering the provided zone; at the same
> + * time each registered zone height in such a tree is accounted for and each
> + * zone, once registered, is stored in the @registered_zones array that is
> + * indexed by zone height: this way will be trivial, at unregister time, to walk
> + * the @registered_zones array backward and unregister all the zones starting
> + * from the leaves, removing children zones before parents.
> + *
> + * While doing this, we prune away any zone marked as invalid (like the ones
> + * sporting an SCMI abstract power scale) as long as they are positioned as
> + * leaves in the SCMI powercap zones hierarchy: any non-leaf invalid zone causes
> + * the entire process to fail since we cannot assume the correctness of an SCMI
> + * powercap zones hierarchy if some of the internal nodes are missing.
> + *
> + * Note that the array of SCMI powercap zones as returned by the SCMI platform
> + * is known to be sane, i.e. zones relationships have been validated at the
> + * protocol layer.
> + *
> + * Return: 0 on Success
> + */
> +static int scmi_powercap_register_zone(struct scmi_powercap_root *pr,
> +                                      struct scmi_powercap_zone *spz)
> +{
> +       int ret = 0;
> +       struct scmi_powercap_zone *parent;
> +
> +       if (!spz->info)
> +               return ret;
> +
> +       parent = scmi_powercap_get_parent_zone(spz);
> +       if (parent && !scmi_powercap_is_zone_registered(parent)) {
> +               /*
> +                * Bail out if a parent domain was marked as unsupported:
> +                * only domains participating as leaves can be skipped.
> +                */
> +               if (!parent->info)
> +                       return -ENODEV;
> +
> +               ret = scmi_powercap_register_zone(pr, parent);
> +               if (ret)
> +                       return ret;
> +       }
> +
> +       if (!scmi_powercap_is_zone_registered(spz)) {
> +               struct powercap_zone *z;
> +
> +               z = powercap_register_zone(&spz->zone,
> +                                          scmi_top_pcntrl,
> +                                          spz->info->name,
> +                                          parent ? &parent->zone : NULL,
> +                                          &zone_ops, 1, &constraint_ops);
> +               if (!IS_ERR(z)) {
> +                       spz->height = scmi_powercap_get_zone_height(spz);
> +                       list_add(&spz->node,
> +                                &pr->registered_zones[spz->height]);
> +                       dev_dbg(spz->dev,
> +                               "Registered node %s - parent %s - height:%d\n",
> +                               spz->info->name,
> +                               parent ? parent->info->name : "ROOT",
> +                               spz->height);
> +                       ret = 0;
> +               } else {
> +                       ret = PTR_ERR(z);
> +                       dev_err(spz->dev,
> +                               "Error registering node:%s - parent:%s - h:%d - ret:%d\n",
> +                                spz->info->name,
> +                                parent ? parent->info->name : "ROOT",
> +                                spz->height, ret);
> +               }
> +       }
> +
> +       return ret;
> +}
> +
> +static int scmi_powercap_probe(struct scmi_device *sdev)
> +{
> +       int ret, i;
> +       struct scmi_powercap_root *pr;
> +       struct scmi_powercap_zone *spz;
> +       struct scmi_protocol_handle *ph;
> +       struct device *dev = &sdev->dev;
> +
> +       if (!sdev->handle)
> +               return -ENODEV;
> +
> +       powercap_ops = sdev->handle->devm_protocol_get(sdev,
> +                                                      SCMI_PROTOCOL_POWERCAP,
> +                                                      &ph);
> +       if (IS_ERR(powercap_ops))
> +               return PTR_ERR(powercap_ops);
> +
> +       pr = devm_kzalloc(dev, sizeof(*pr), GFP_KERNEL);
> +       if (!pr)
> +               return -ENOMEM;
> +
> +       pr->num_zones = powercap_ops->num_domains_get(ph);
> +       if (pr->num_zones < 0) {
> +               dev_err(dev, "number of powercap domains not found\n");
> +               return pr->num_zones;
> +       }
> +
> +       pr->spzones = devm_kcalloc(dev, pr->num_zones,
> +                                  sizeof(*pr->spzones), GFP_KERNEL);
> +       if (!pr->spzones)
> +               return -ENOMEM;
> +
> +       /* Allocate for worst possible scenario of maximum tree height. */
> +       pr->registered_zones = devm_kcalloc(dev, pr->num_zones,
> +                                           sizeof(*pr->registered_zones),
> +                                           GFP_KERNEL);
> +       if (!pr->registered_zones)
> +               return -ENOMEM;
> +
> +       for (i = 0, spz = pr->spzones; i < pr->num_zones; i++, spz++) {
> +               /*
> +                * Powercap domains are validate by the protocol layer, i.e.
> +                * when only non-NULL domains are returned here, whose
> +                * parent_id is assured to point to another valid domain.
> +                */
> +               spz->info = powercap_ops->info_get(ph, i);
> +
> +               spz->dev = dev;
> +               spz->ph = ph;
> +               spz->spzones = pr->spzones;
> +               INIT_LIST_HEAD(&spz->node);
> +               INIT_LIST_HEAD(&pr->registered_zones[i]);
> +
> +               /*
> +                * Forcibly skip powercap domains using an abstract scale.
> +                * Note that only leaves domains can be skipped, so this could
> +                * lead later to a global failure.
> +                */
> +               if (!spz->info->powercap_scale_uw &&
> +                   !spz->info->powercap_scale_mw) {
> +                       dev_warn(dev,
> +                                "Abstract power scale not supported. Skip %s.\n",
> +                                spz->info->name);
> +                       spz->info = NULL;
> +                       continue;
> +               }
> +       }
> +
> +       /*
> +        * Scan array of retrieved SCMI powercap domains and register them
> +        * recursively starting from the root domains.
> +        */
> +       for (i = 0, spz = pr->spzones; i < pr->num_zones; i++, spz++) {
> +               ret = scmi_powercap_register_zone(pr, spz);
> +               if (ret) {
> +                       dev_err(dev,
> +                               "Failed to register powercap zone %s - ret:%d\n",
> +                               spz->info->name, ret);
> +                       scmi_powercap_unregister_all_zones(pr);
> +                       return ret;
> +               }
> +       }
> +
> +       dev_set_drvdata(dev, pr);
> +
> +       dev_info(dev, "Registered %d SCMI Powercap domains !\n", pr->num_zones);
> +
> +       return ret;
> +}
> +
> +static void scmi_powercap_remove(struct scmi_device *sdev)
> +{
> +       struct device *dev = &sdev->dev;
> +       struct scmi_powercap_root *pr = dev_get_drvdata(dev);
> +
> +       scmi_powercap_unregister_all_zones(pr);
> +}
> +
> +static const struct scmi_device_id scmi_id_table[] = {
> +       { SCMI_PROTOCOL_POWERCAP, "powercap" },
> +       { },
> +};
> +MODULE_DEVICE_TABLE(scmi, scmi_id_table);
> +
> +static struct scmi_driver scmi_powercap_driver = {
> +       .name = "scmi-powercap",
> +       .probe = scmi_powercap_probe,
> +       .remove = scmi_powercap_remove,
> +       .id_table = scmi_id_table,
> +};
> +
> +static int __init scmi_powercap_init(void)
> +{
> +       int ret;
> +
> +       scmi_top_pcntrl = powercap_register_control_type(NULL, "arm-scmi", NULL);
> +       if (!scmi_top_pcntrl)
> +               return -ENODEV;
> +
> +       ret = scmi_register(&scmi_powercap_driver);
> +       if (ret)
> +               powercap_unregister_control_type(scmi_top_pcntrl);
> +
> +       return ret;
> +}
> +module_init(scmi_powercap_init);
> +
> +static void __exit scmi_powercap_exit(void)
> +{
> +       scmi_unregister(&scmi_powercap_driver);
> +
> +       powercap_unregister_control_type(scmi_top_pcntrl);
> +}
> +module_exit(scmi_powercap_exit);
> +
> +MODULE_AUTHOR("Cristian Marussi <cristian.marussi@xxxxxxx>");
> +MODULE_DESCRIPTION("ARM SCMI Powercap driver");
> +MODULE_LICENSE("GPL");
> --
> 2.32.0
>