Subject: Re: [PATCH v5 09/12] firmware: arm_scmi: add Powercap MAI get/set support

From: Cristian Marussi <[email-masked]>
Date: Tue, 5 May 2026 21:36:26 +0100

On Tue, Apr 28, 2026 at 10:09:18AM +0100, Philip Radford wrote:
> Add support for Power Measurement Averaging Interval (MAI)

Hi,

> get and set operations to the SCMI powercap protocol driver.
> Extends scmi_powercap_info to store MAI configuration and
> implement MAI get/set via xfer and optional fast-channel
> support.

You have to stay under 75 chars...ok...but I'd say this commit message
lines are way to short...you can stretch a bit more towards 75chars
without having to split words I think....because

t
o
o

s
h
o
r
t

l
i
n
e
s

are not so good anyway :P

> 
> Signed-off-by: Philip Radford <[email-masked]>
> ---
>  drivers/firmware/arm_scmi/powercap.c | 120 +++++++++++++++++++++++++++
>  include/linux/scmi_protocol.h        |   8 ++
>  2 files changed, 128 insertions(+)
> 
> diff --git a/drivers/firmware/arm_scmi/powercap.c b/drivers/firmware/arm_scmi/powercap.c
> index 86262eb0f34a..b5879f204b5e 100644
> --- a/drivers/firmware/arm_scmi/powercap.c
> +++ b/drivers/firmware/arm_scmi/powercap.c
> @@ -401,6 +401,34 @@ scmi_powercap_domain_attrs_process(const struct scmi_protocol_handle *ph,
>  		dom_info->notify_powercap_measurement_change =
>  			SUPPORTS_POWERCAP_MEASUREMENTS_CHANGE_NOTIFY(flags);
>  
> +	if (PROTOCOL_REV_MAJOR(ph->version) >= 0x3) {
> +		struct scmi_msg_resp_powercap_domain_attributes_v3 *resp_v3 = r;
> +
> +		flags = le32_to_cpu(resp_v3->attributes);
> +		if (pinfo->notify_measurements_cmd)
> +			dom_info->notify_powercap_measurement_change =
> +			       SUPPORTS_POWERCAP_MEASUREMENTS_CHANGE_NOTIFY(flags);
> +
> +		dom_info->mai_config = SUPPORTS_POWERCAP_MAI_CONFIGURATION(flags);
> +		dom_info->min_mai = le32_to_cpu(resp_v3->min_mai);
> +		dom_info->max_mai = le32_to_cpu(resp_v3->max_mai);
> +		dom_info->mai_step = le32_to_cpu(resp_v3->mai_step);
> +
> +		if (dom_info->mai_config) {
> +			ret = scmi_powercap_validate(dom_info->min_mai,
> +						     dom_info->max_mai,
> +						     dom_info->mai_step,
> +						     dom_info->mai_config);
> +
> +			if (ret) {
> +				dev_warn(ph->dev, "Platform reported problem MAI config for domain %d - %s\n",

"....reported invalid MAI config for domain..."

> +					 dom_info->id, dom_info->name);
> +
> +				return ret;
> +			}
> +		}
> +	}
> +
>  	dom_info->extended_names = SUPPORTS_EXTENDED_NAMES(flags);
>  
>  	dom_info->async_powercap_cap_set =
> @@ -1082,6 +1110,96 @@ static int scmi_powercap_cap_enable_get(const struct scmi_protocol_handle *ph,
>  	return 0;
>  }
>  
> +static int scmi_powercap_xfer_mai_get(const struct scmi_protocol_handle *ph, u32 domain_id,
> +				      u32 *mai)

..bad alignment and till now we try still to stick tpo 80cols in the SCMI
stack if it does NOT really hamper readability...

> +{
> +	int ret;
> +	struct scmi_xfer *t;
> +
> +	ret = ph->xops->xfer_get_init(ph, POWERCAP_MAI_GET, sizeof(u32),
> +								sizeof(u32), &t);

...terrible alignment...and you know why :D

> +
> +	if (ret)
> +		return ret;
> +
> +	put_unaligned_le32(domain_id, t->tx.buf);
> +
> +	ret = ph->xops->do_xfer(ph, t);
> +	if (!ret)
> +		*mai = get_unaligned_le32(t->rx.buf);
> +
> +	ph->xops->xfer_put(ph, t);
> +	return ret;
> +}
> +
> +static int scmi_powercap_xfer_mai_set(const struct scmi_protocol_handle *ph, u32 domain_id, u32 mai)

..same...try to stick to 80 cols when not impossibly ugly..

> +{
> +	int ret;
> +	struct scmi_xfer *t;
> +	struct scmi_msg_powercap_cap_or_pai_set *msg;
> +
> +	ret = ph->xops->xfer_get_init(ph, POWERCAP_MAI_SET, sizeof(*msg), 0, &t);

same

> +	if (ret)
> +		return ret;
> +
> +	msg = t->tx.buf;
> +	msg->domain_id = cpu_to_le32(domain_id);
> +	msg->flags = cpu_to_le32(0);
> +	msg->value = cpu_to_le32(mai);
> +
> +	ret = ph->xops->do_xfer(ph, t);
> +
> +	ph->xops->xfer_put(ph, t);
> +	return ret;
> +}
> +
> +static int scmi_powercap_measurements_interval_get(const struct scmi_protocol_handle *ph,
> +						   u32 domain_id, u32 *val)
> +{

ditto

> +	const struct scmi_powercap_info *pc;
> +	struct scmi_fc_info *fci;
> +
> +	if (!val)
> +		return -EINVAL;
> +
> +	pc = scmi_powercap_dom_info_get(ph, domain_id);
> +	if (!pc)
> +		return -EINVAL;
> +
> +	fci = pc->cpli[CPL0].fc_info;
> +	if (fci && fci[POWERCAP_FC_MAI].get_addr) {
> +		*val = ioread32(fci[POWERCAP_FC_MAI].get_addr);
> +		trace_scmi_fc_call(SCMI_PROTOCOL_POWERCAP, POWERCAP_MAI_GET, domain_id, 0, *val, 0);
ditto
> +		return 0;
> +	}
> +
> +	return scmi_powercap_xfer_mai_get(ph, domain_id, val);
> +}
> +
> +static int scmi_powercap_measurements_interval_set(const struct scmi_protocol_handle *ph,
> +						   u32 domain_id, u32 val)
> +{

ditto

> +	const struct scmi_powercap_info *pc;
> +	struct scmi_fc_info *fci;
> +
> +	pc = scmi_powercap_dom_info_get(ph, domain_id);
> +	if (!pc)
> +		return -EINVAL;
> +
> +	if (!pc->mai_config || !val || val < pc->min_mai || val > pc->max_mai)
> +		return -EINVAL;
> +
> +	fci = pc->cpli[CPL0].fc_info;
> +	if (fci && fci[POWERCAP_FC_MAI].set_addr) {
> +		iowrite32(val, fci[POWERCAP_FC_MAI].set_addr);
> +		ph->hops->fastchannel_db_ring(fci[POWERCAP_FC_MAI].set_db);
> +		trace_scmi_fc_call(SCMI_PROTOCOL_POWERCAP, POWERCAP_MAI_SET, domain_id, 0, val, 0);
> +		return 0;
> +	}
> +
> +	return scmi_powercap_xfer_mai_set(ph, domain_id, val);
> +}
> +
>  static const struct scmi_powercap_proto_ops powercap_proto_ops = {
>  	.num_domains_get = scmi_powercap_num_domains_get,
>  	.info_get = scmi_powercap_dom_info_get,
> @@ -1094,6 +1212,8 @@ static const struct scmi_powercap_proto_ops powercap_proto_ops = {
>  	.measurements_get = scmi_powercap_measurements_get,
>  	.measurements_threshold_set = scmi_powercap_measurements_threshold_set,
>  	.measurements_threshold_get = scmi_powercap_measurements_threshold_get,
> +	.measurements_interval_get = scmi_powercap_measurements_interval_get,
> +	.measurements_interval_set = scmi_powercap_measurements_interval_set,
>  };
>  
>  static void scmi_powercap_domain_init_fc(const struct scmi_protocol_handle *ph,
> diff --git a/include/linux/scmi_protocol.h b/include/linux/scmi_protocol.h
> index d0f6c0102559..73d66281dcc3 100644
> --- a/include/linux/scmi_protocol.h
> +++ b/include/linux/scmi_protocol.h
> @@ -675,6 +675,10 @@ struct scmi_powercap_info {
>  	bool powercap_scale_uw;
>  	bool extended_names;
>  	bool fastchannels;
> +	bool mai_config;
> +	u32 min_mai;
> +	u32 max_mai;
> +	u32 mai_step;

No docs for new fields ?

>  	char name[SCMI_MAX_STR_SIZE];
>  	unsigned int sustainable_power;
>  	unsigned int accuracy;
> @@ -758,6 +762,10 @@ struct scmi_powercap_proto_ops {
>  	int (*measurements_threshold_get)(const struct scmi_protocol_handle *ph,
>  					  u32 domain_id, u32 *power_thresh_low,
>  					  u32 *power_thresh_high);
> +	int (*measurements_interval_get)(const struct scmi_protocol_handle *ph,
> +					 u32 domain_id, u32 *val);
> +	int (*measurements_interval_set)(const struct scmi_protocol_handle *ph,
> +					 u32 domain_id, u32 val);

No docs for new fields ?

Thanks,
Cristian