Re: [PATCH v5 06/12] firmware: arm_scmi: Extend powercap report to include MAI

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

On Tue, May 05, 2026 at 09:13:32PM +0100, Cristian Marussi wrote:
> On Tue, Apr 28, 2026 at 10:09:15AM +0100, Philip Radford wrote:
> > Extend scmi_powercap_meas_changed_report to include MAI change
> > notifications.
> > 
> 
> Hi
> 

Hi,
Thanks for the review.

> > Signed-off-by: Philip Radford <philip.radford@arm.com>
> > ---
> >  drivers/firmware/arm_scmi/powercap.c | 20 ++++++++++++--------
> >  include/linux/scmi_protocol.h        |  1 +
> >  2 files changed, 13 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/firmware/arm_scmi/powercap.c b/drivers/firmware/arm_scmi/powercap.c
> > index 1d1188e98d49..b9d50f4e8ae5 100644
> > --- a/drivers/firmware/arm_scmi/powercap.c
> > +++ b/drivers/firmware/arm_scmi/powercap.c
> > @@ -11,6 +11,7 @@
> >  #include <linux/io.h>
> >  #include <linux/module.h>
> >  #include <linux/scmi_protocol.h>
> > +#include <linux/stddef.h>
> >  
> >  #include <trace/events/scmi.h>
> >  
> > @@ -164,6 +165,7 @@ struct scmi_powercap_meas_changed_notify_payld {
> >  	__le32 agent_id;
> >  	__le32 domain_id;
> >  	__le32 power;
> > +	__le32 mai;
> >  };
> >  
> >  struct scmi_msg_powercap_cpc {
> > @@ -1212,13 +1214,6 @@ static int scmi_powercap_notify(const struct scmi_protocol_handle *ph,
> >  		if (ret)
> >  			return ret;
> >  
> > -		if (enable && !low && !high) {
> > -			dev_err(ph->dev,
> > -				"Invalid Measurements Notify thresholds: %u/%u\n",
> > -				low, high);
> > -			return -EINVAL;
> > -		}
> > -
> 
> Ok so you removed this check because now that a notification can be
> emitted even only to notify a MAI change, it is possible that the
> thresholds are zero and the notification will be emitted anyway due to
> a MAI change....BUT you have to review or completely remove the comment
> block that precedes this that says:
> 
>    /*                                                               
>     * Note that we have to pick the most recently configured        
>     * thresholds to build a proper POWERCAP_MEASUREMENTS_NOTIFY     
>     * enable request and we fail, complaining, if no thresholds     
>     * were ever set, since this is an indication the API has been   
>     * used wrongly.                                                 
>     */                                                              
> 
> ...becasue NOW is no more true and misleading, since you just removed the
> fail and complain part...
> 
> It would be good to shortly explain in a comment the new possible
> scenarios in which notification can be enabled...
> 

Apologies, I have overlooked this comment. I will amend it.

> >  		ret = ph->xops->xfer_get_init(ph, message_id,
> >  					      sizeof(*notify), 0, &t);
> >  		if (ret)
> > @@ -1333,14 +1328,23 @@ scmi_powercap_fill_custom_report(const struct scmi_protocol_handle *ph,
> >  	{
> >  		const struct scmi_powercap_meas_changed_notify_payld *p = payld;
> >  		struct scmi_powercap_meas_changed_report *r = report;
> > +		const size_t sz_v2 = offsetofend(struct scmi_powercap_meas_changed_notify_payld,
> > +						 power);
> > +		const size_t sz_v3 = sizeof(*p);
> 
> While this is a valid and nice construct, I think is overkill here since
> these offsets/sizes will never change at runtime....
> 
> ...you can just define above a couples of DEFINE that hardcodes the
> sizes of the v2 and v3 by using the
> 
> 	#define SZ_V2 	(sizeof(struct scmi_powercap_meas_changed_notify_payld))
> 
> and
> 	#define SZ_V3   (SZ_V2 - sizeof(__le32))
> 

Noted, will do.

> >  
> > -		if (sizeof(*p) != payld_sz)
> > +		if (payld_sz != sz_v2 && payld_sz != sz_v3)
> >  			break;
> >  
> >  		r->timestamp = timestamp;
> >  		r->agent_id = le32_to_cpu(p->agent_id);
> >  		r->domain_id = le32_to_cpu(p->domain_id);
> >  		r->power = le32_to_cpu(p->power);
> 
> maybe more clear to simply:
> 		
> 		r->mai = 0;
> 		if (payld_sz == SZ_V3 && PROTOCOL_REV_MAJOR(ph->version) >= 0x3)
> 			r->mai = le32_to_cpu(p->mai);
> 
> 	

Agreed.
	
> > +
> > +		if (payld_sz == sz_v3 && PROTOCOL_REV_MAJOR(ph->version) >= 0x3)
> > +			r->mai = le32_to_cpu(p->mai);
> > +		else
> > +			r->mai = 0;
> > +
> >  		*src_id = r->domain_id;
> 

Thanks,
Phil