[PATCH v9 04/13] firmware: arm_scmi: Add SCMIv4.0 Powercap basic support
Sudeep Holla
sudeep.holla at kernel.org
Thu Oct 15 05:57:14 PDT 2026
On Wed, Sep 09, 2026 at 10:04:28PM +0000, Philip Radford wrote:
> From: Cristian Marussi <cristian.marussi at arm.com>
>
> Add SCMIv4.0 Powercap support for enumerating multiple CPLs of a domain
> when available.
>
> Signed-off-by: Cristian Marussi <cristian.marussi at arm.com>
> [Philip: Fixed sparse issues where int was expected]
> Signed-off-by: Philip Radford <philip.radford at arm.com>
> ---
> V8->V9
> - included validation of the number of cpls in iter_powercap_cpls_update_state
> - re-ordered validation of cap_config and num_cpli in powercap_domain_attrs_process
> - included validation of length in powercap_domain_attributes_get
> - amended cap_get and cap_set referencing apl_id array index instead fo firmware CPL identifier
> - added bounds check to make sure cpl_id is less than num_cpli
> ---
> drivers/firmware/arm_scmi/powercap.c | 495 ++++++++++++++++++++++-----
> drivers/powercap/arm_scmi_powercap.c | 2 +-
> include/linux/scmi_protocol.h | 1 +
> 3 files changed, 402 insertions(+), 96 deletions(-)
>
> diff --git a/drivers/firmware/arm_scmi/powercap.c b/drivers/firmware/arm_scmi/powercap.c
> index 4666030176c3..7ee39434a4db 100644
> --- a/drivers/firmware/arm_scmi/powercap.c
> +++ b/drivers/firmware/arm_scmi/powercap.c
> @@ -33,6 +33,7 @@ enum scmi_powercap_protocol_cmd {
> POWERCAP_CAP_NOTIFY = 0xa,
> POWERCAP_MEASUREMENTS_NOTIFY = 0xb,
> POWERCAP_DESCRIBE_FASTCHANNEL = 0xc,
> + POWERCAP_CPC_ATTRIBUTES = 0xd,
> };
>
> enum {
> @@ -69,17 +70,56 @@ struct scmi_msg_resp_powercap_domain_attributes {
> __le32 parent_id;
> };
>
> +struct scmi_msg_resp_powercap_domain_attributes_v3 {
> + __le32 attributes;
> +#define SUPPORTS_POWERCAP_MAI_CONFIGURATION(x) ((x) & BIT(25))
> +#define SUPPORTS_POWERCAP_FASTCHANNELS(x) ((x) & BIT(22))
> +#define SUPPORTS_POWERCAP_CAP_CHANGE_NOTIFY_V3(x) ((x) & BIT(21))
> +#define SUPPORTS_POWERCAP_CAI_CONFIGURATION(x) ((x) & BIT(20))
> + u8 name[SCMI_SHORT_NAME_MAX_SIZE];
> + __le32 min_mai;
> + __le32 max_mai;
> + __le32 mai_step;
> + __le32 min_power_cap;
> + __le32 max_power_cap;
> + __le32 power_cap_step;
> + __le32 sustainable_power;
> + __le32 accuracy;
> + __le32 parent_id;
> + __le32 min_cai;
> + __le32 max_cai;
> + __le32 cai_step;
> +};
> +
> +struct scmi_msg_powercap_get_v3 {
> + __le32 domain_id;
> + __le32 cpli;
> +};
> +
> struct scmi_msg_powercap_set_cap_or_pai {
> - __le32 domain;
> + __le32 domain_id;
> __le32 flags;
> #define CAP_SET_ASYNC BIT(1)
> #define CAP_SET_IGNORE_DRESP BIT(0)
> __le32 value;
> };
>
> +struct scmi_msg_powercap_set_cap_v3 {
> + __le32 domain_id;
> + __le32 cpli;
> + __le32 flags;
> + __le32 power_cap;
> +};
> +
> struct scmi_msg_resp_powercap_cap_set_complete {
> - __le32 domain;
> + __le32 domain_id;
> + __le32 power_cap;
> +};
> +
> +struct scmi_msg_resp_powercap_cap_set_complete_v3 {
> + __le32 domain_id;
> __le32 power_cap;
> + __le32 cpli;
> };
>
> struct scmi_msg_resp_powercap_meas_get {
> @@ -112,6 +152,33 @@ struct scmi_powercap_meas_changed_notify_payld {
> __le32 power;
> };
>
> +struct scmi_msg_powercap_cpc {
> + __le32 domain_id;
> + __le32 desc_index;
> +};
> +
> +struct scmi_msg_resp_powercap_cpc {
> + __le32 num_cpl;
> +#define NUM_RETURNED(n) (le32_get_bits((n), GENMASK(15, 0)))
> +#define NUM_REMAINING(n) (le32_get_bits((n), GENMASK(31, 16)))
> + struct {
> + __le32 cpli;
> + __le32 flags;
> + __le32 min_power_cap;
> + __le32 max_power_cap;
> + __le32 power_cap_step;
> + __le32 min_cai;
> + __le32 max_cai;
> + __le32 cai_step;
> + u8 name[SCMI_SHORT_NAME_MAX_SIZE];
> + } desc[];
> +};
> +
> +struct scmi_cpls_priv {
> + u32 domain_id;
> + struct scmi_powercap_cpl_info *cpli;
> +};
> +
> struct scmi_powercap_state {
> bool enabled;
> u32 last_pcap;
> @@ -129,6 +196,11 @@ struct powercap_info {
> bool notify_measurements_cmd;
> struct scmi_powercap_state *states;
> struct scmi_powercap_info *powercaps;
> + int (*xfer_cap_get)(const struct scmi_protocol_handle *ph,
> + const struct scmi_powercap_info *pc, u32 cpl_id, u32 *power_cap);
> + int (*xfer_cap_set)(const struct scmi_protocol_handle *ph,
> + const struct scmi_powercap_info *pc,
> + u32 cpl_id, u32 power_cap, bool ignore_dresp);
> };
>
> static enum scmi_powercap_protocol_cmd evt_2_cmd[] = {
> @@ -192,18 +264,227 @@ scmi_powercap_validate(unsigned int min_val, unsigned int max_val,
> return 0;
> }
>
> +static void iter_powercap_cpls_prepare_message(void *message,
> + unsigned int desc_index,
> + const void *priv)
> +{
> + struct scmi_msg_powercap_cpc *msg = message;
> + const struct scmi_cpls_priv *p = priv;
> +
> + msg->domain_id = cpu_to_le32(p->domain_id);
> + msg->desc_index = cpu_to_le32(desc_index);
> +}
> +
> +static int iter_powercap_cpls_update_state(struct scmi_iterator_state *st,
> + const void *response, void *priv)
> +{
> + const struct scmi_msg_resp_powercap_cpc *r = response;
> + size_t needed;
> +
> + if (st->rx_len < sizeof(r->num_cpl))
> + return -EPROTO;
> +
> + st->num_returned = NUM_RETURNED(r->num_cpl);
> + st->num_remaining = NUM_REMAINING(r->num_cpl);
> +
> + needed = struct_size(r, desc, st->num_returned);
> + if (st->rx_len < needed)
> + return -EPROTO;
> +
> + return 0;
> +}
> +
> +static int
> +iter_powercap_cpls_process_response(const struct scmi_protocol_handle *ph,
> + const void *response,
> + struct scmi_iterator_state *st, void *priv)
> +{
> + const struct scmi_msg_resp_powercap_cpc *r = response;
> + struct scmi_cpls_priv *p = priv;
> + struct scmi_powercap_cpl_info *cpl;
> +
> + cpl = &p->cpli[st->desc_index + st->loop_idx];
> +
> + cpl->id = le32_to_cpu(r->desc[st->loop_idx].cpli);
> + cpl->cap_config = le32_to_cpu(r->desc[st->loop_idx].flags) & BIT(0);
> +
> + cpl->min_power_cap = le32_to_cpu(r->desc[st->loop_idx].min_power_cap);
> + cpl->max_power_cap = le32_to_cpu(r->desc[st->loop_idx].max_power_cap);
> + cpl->power_cap_step = le32_to_cpu(r->desc[st->loop_idx].power_cap_step);
> + if (!cpl->power_cap_step && cpl->min_power_cap != cpl->max_power_cap)
> + return -EINVAL;
> +
> + cpl->min_avg_ivl = le32_to_cpu(r->desc[st->loop_idx].min_cai);
> + cpl->max_avg_ivl = le32_to_cpu(r->desc[st->loop_idx].max_cai);
> + cpl->avg_ivl_step = le32_to_cpu(r->desc[st->loop_idx].cai_step);
> + if (!cpl->avg_ivl_step && cpl->min_avg_ivl != cpl->max_avg_ivl)
> + return -EINVAL;
> +
> + cpl->avg_ivl_config = cpl->min_avg_ivl != cpl->max_avg_ivl;
> +
> + strscpy(cpl->name, r->desc[st->loop_idx].name, SCMI_SHORT_NAME_MAX_SIZE);
> +
> + return 0;
> +}
> +
> +static int scmi_powercap_cpls_enumerate(const struct scmi_protocol_handle *ph,
> + struct scmi_powercap_info *dom_info)
> +{
> + void *iter;
> + struct scmi_iterator_ops ops = {
> + .prepare_message = iter_powercap_cpls_prepare_message,
> + .update_state = iter_powercap_cpls_update_state,
> + .process_response = iter_powercap_cpls_process_response,
> + };
> + struct scmi_cpls_priv cpriv = {
> + .domain_id = dom_info->id,
> + .cpli = dom_info->cpli,
> + };
> +
> + iter = ph->hops->iter_response_init(ph, &ops, dom_info->num_cpli,
> + POWERCAP_CPC_ATTRIBUTES,
> + sizeof(struct scmi_msg_powercap_cpc),
> + &cpriv);
> + if (IS_ERR(iter))
> + return PTR_ERR(iter);
> +
> + return ph->hops->iter_response_run(iter);
> +}
> +
> +static int
> +scmi_powercap_domain_attrs_process(const struct scmi_protocol_handle *ph,
> + struct powercap_info *pinfo,
> + struct scmi_powercap_info *dom_info, void *r)
> +{
> + struct scmi_msg_resp_powercap_domain_attributes *resp = r;
> + u32 flags = le32_to_cpu(resp->attributes);
> + bool cap_config;
> + int ret;
> +
> + cap_config = SUPPORTS_POWERCAP_CAP_CONFIGURATION(flags);
> + if (PROTOCOL_REV_MAJOR(ph->version) < 0x3) {
> + dom_info->num_cpli = 1;
> + } else {
> + dom_info->num_cpli = le32_get_bits(resp->attributes,
> + GENMASK(18, 15));
> +
> + if (cap_config && !dom_info->num_cpli)
> + return -EINVAL;
> +
> + if (!dom_info->num_cpli)
> + dom_info->num_cpli = 1;
> + }
> +
> + dom_info->cpli = devm_kcalloc(ph->dev, dom_info->num_cpli,
> + sizeof(*dom_info->cpli), GFP_KERNEL);
> + if (!dom_info->cpli)
> + return -ENOMEM;
> +
> + if (pinfo->notify_cap_cmd) {
> + if (PROTOCOL_REV_MAJOR(ph->version) < 0x3)
> + dom_info->notify_powercap_cap_change =
> + SUPPORTS_POWERCAP_CAP_CHANGE_NOTIFY(flags);
> + else
> + dom_info->notify_powercap_cap_change =
> + SUPPORTS_POWERCAP_CAP_CHANGE_NOTIFY_V3(flags);
> + }
> +
> + if (pinfo->notify_measurements_cmd)
> + dom_info->notify_powercap_measurement_change =
> + SUPPORTS_POWERCAP_MEASUREMENTS_CHANGE_NOTIFY(flags);
> +
> + dom_info->extended_names = SUPPORTS_EXTENDED_NAMES(flags);
> +
> + dom_info->async_powercap_cap_set =
> + SUPPORTS_ASYNC_POWERCAP_CAP_SET(flags);
> +
> + dom_info->powercap_monitoring =
> + SUPPORTS_POWERCAP_MONITORING(flags);
> + dom_info->powercap_scale_mw =
> + SUPPORTS_POWER_UNITS_MW(flags);
> + dom_info->powercap_scale_uw =
> + SUPPORTS_POWER_UNITS_UW(flags);
> + dom_info->fastchannels =
> + SUPPORTS_POWERCAP_FASTCHANNELS(flags);
> +
> + strscpy(dom_info->name, resp->name, SCMI_SHORT_NAME_MAX_SIZE);
> +
> + dom_info->sustainable_power =
> + le32_to_cpu(resp->sustainable_power);
> + dom_info->accuracy = le32_to_cpu(resp->accuracy);
> +
> + dom_info->parent_id = le32_to_cpu(resp->parent_id);
> + if (dom_info->parent_id != SCMI_POWERCAP_ROOT_ZONE_ID &&
> + (dom_info->parent_id >= pinfo->num_domains ||
> + dom_info->parent_id == dom_info->id)) {
> + dev_err(ph->dev,
> + "Platform reported inconsistent parent ID for domain %d - %s\n",
> + dom_info->id, dom_info->name);
> + return -ENODEV;
> + }
> +
> + dom_info->cpli[0].id = CPL0;
> + if (PROTOCOL_REV_MAJOR(ph->version) < 0x3)
> + dom_info->cpli[0].avg_ivl_config =
> + SUPPORTS_POWERCAP_PAI_CONFIGURATION(flags);
> + else
> + dom_info->cpli[0].avg_ivl_config =
> + SUPPORTS_POWERCAP_CAI_CONFIGURATION(flags);
> +
> + if (PROTOCOL_REV_MAJOR(ph->version) < 0x3) {
> + dom_info->cpli[0].min_avg_ivl = le32_to_cpu(resp->min_pai);
> + dom_info->cpli[0].max_avg_ivl = le32_to_cpu(resp->max_pai);
> + dom_info->cpli[0].avg_ivl_step = le32_to_cpu(resp->pai_step);
> + } else {
> + struct scmi_msg_resp_powercap_domain_attributes_v3 *resp = r;
> +
> + dom_info->cpli[0].min_avg_ivl = le32_to_cpu(resp->min_cai);
> + dom_info->cpli[0].max_avg_ivl = le32_to_cpu(resp->max_cai);
> + dom_info->cpli[0].avg_ivl_step = le32_to_cpu(resp->cai_step);
> + }
> +
> + ret = scmi_powercap_validate(dom_info->cpli[0].min_avg_ivl,
> + dom_info->cpli[0].max_avg_ivl,
> + dom_info->cpli[0].avg_ivl_step,
> + dom_info->cpli[0].avg_ivl_config);
This could be existing bug w.r.t conformance as we are supposed to allow
0 as valid CAI and MAI values. It may need fixing with current PAI handling
and we need to avoid using the same check on CAI.
The spec states: "The platform may choose not to report CAI or MAI".
Please take a look and fix the existing bug and the one in this series
that applies for CAI.
I am just looking at conformance for now.
--
Regards,
Sudeep
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