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

Philip Radford
2026-05-05T21:21:35Z

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