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

[Philip Radford <philip.radford@arm.com>]

On Tue, May 05, 2026 at 09:36:26PM +0100, Cristian Marussi wrote:
> On Tue, Apr 28, 2026 at 10:09:18AM +0100, Philip Radford wrote:
> > Add support for Power Measurement Averaging Interval (MAI)
> 
> Hi,
> 

Hi,
Thanks for the review.

> > 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
> 

Noted. I was too concerned about going over the limit and didn't think
about the opposite being an issue.

> > 
> > Signed-off-by: Philip Radford <philip.radford@arm.com>
> > ---
> >  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..."
> 

Noted, will change.

> > +					 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...
> 

I will address this, but I'm quite certain it wasn't flagged by checkpatch.

> > +{
> > +	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
> 

Will address.

> > +
> > +	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..
> 

Will do.

> > +{
> > +	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
> 

I'm not sure why I split that over two lines, will change.

> > +	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
> 

Will do.

> > +	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

Noted

> > +		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
> 

Noted.

> > +	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 ?
> 

Will add them.

> >  	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 ?
> 

Will add them.
And will pay more attention to col length from now on.

Regards,
Phil.