On Thu, Mar 19, 2026 at 01:39:40PM +0100, Marcin Ślusarz wrote:
> On Thu, Mar 19, 2026 at 11:43:45AM +0000, Liviu Dudau wrote:
> > Hi Marcin,
> >
> > On Thu, Mar 19, 2026 at 12:00:53PM +0100, Marcin Slusarz wrote:
> > > ...
> > > +#define VALID_TIMESTAMP_QUERY_FLAGS \
> > > + (DRM_PANTHOR_TIMESTAMP_GPU | \
> > > + DRM_PANTHOR_TIMESTAMP_CPU_TYPE_MASK | \
> > > + DRM_PANTHOR_TIMESTAMP_GPU_OFFSET | \
> > > + DRM_PANTHOR_TIMESTAMP_GPU_CYCLE_COUNT | \
> > > + DRM_PANTHOR_TIMESTAMP_FREQ | \
> > > + DRM_PANTHOR_TIMESTAMP_DURATION)
> > > +
> > > static int panthor_query_timestamp_info(struct panthor_device *ptdev,
> > > struct drm_panthor_timestamp_info *arg)
> > > {
> > > int ret;
> > > + u32 flags;
> > > + unsigned long irq_flags;
> > > + struct timespec64 cpu_ts;
> > > + u64 query_start_time;
> > > + bool minimize_interruption;
> > > + u32 timestamp_types = 0;
> > > +
> > > + if (arg->flags != 0) {
> > > + flags = arg->flags;
> > > + } else {
> > > + /*
> > > + * If flags are 0, then ask for the same things that we asked
> > > + * for before flags were added.
> > > + */
> > > + flags = DRM_PANTHOR_TIMESTAMP_GPU |
> > > + DRM_PANTHOR_TIMESTAMP_GPU_OFFSET |
> > > + DRM_PANTHOR_TIMESTAMP_FREQ;
> > > + }
> > > +
> > > + switch (flags & DRM_PANTHOR_TIMESTAMP_CPU_TYPE_MASK) {
> > > + case 0:
>
> Umm, this should be DRM_PANTHOR_TIMESTAMP_CPU_NONE.
>
> > > + break;
> > > + case DRM_PANTHOR_TIMESTAMP_CPU_MONOTONIC:
> > > + case DRM_PANTHOR_TIMESTAMP_CPU_MONOTONIC_RAW:
> > > + timestamp_types++;
> > > + break;
> > > + default:
> > > + return -EINVAL;
> > > + }
> > > +
> > > + if (flags & ~VALID_TIMESTAMP_QUERY_FLAGS)
> > > + return -EINVAL;
> >
> > Can we move this check before the switch and simplify the switch itself to
> > only do the timestamp_types increment?
>
> DRM_PANTHOR_TIMESTAMP_CPU_TYPE_MASK is bit field that holds individual
> clock type values, so we still need to validate the bit field.
The if () test eliminates the default case, and if you change the switch to:
switch (flags & DRM_PANTHOR_TIMESTAMP_CPU_NONE) {
case DRM_PANTHOR_TIMESTAMP_CPU_MONOTONIC:
case DRM_PANTHOR_TIMESTAMP_CPU_MONOTONIC_RAW:
timestamp_types++;
break;
}
then it should be equivalent, right?
>
> > > +
> > > + if (flags & DRM_PANTHOR_TIMESTAMP_GPU)
> > > + timestamp_types++;
> > > + if (flags & DRM_PANTHOR_TIMESTAMP_GPU_CYCLE_COUNT)
> > > + timestamp_types++;
> > > +
> > > + /* If user asked to obtain timestamps from more than one source,
> > > + * then it very likely means they want them to be as close as possible.
> > > + * If they asked for duration, then that likely means that they
> > > + * want to know how long obtaining timestamp takes, without random
> > > + * events, like process scheduling or interrupts.
> > > + */
> >
> > This comment makes me think that user can ask for both CPU_MONOTONIC and
> > CPU_MONOTONIC_RAW timestamps, but the code is built to make them exclusive.
> > Can we document better what sources can be requested simultaneously?
>
> Somethine like this?
>
> diff --git a/include/uapi/drm/panthor_drm.h b/include/uapi/drm/panthor_drm.h
> index 8a46ef040c3d..0e455d91e77d 100644
> --- a/include/uapi/drm/panthor_drm.h
> +++ b/include/uapi/drm/panthor_drm.h
> @@ -466,6 +466,11 @@ struct drm_panthor_timestamp_info {
> * DRM_PANTHOR_TIMESTAMP_GPU |
> * DRM_PANTHOR_TIMESTAMP_GPU_OFFSET |
> * DRM_PANTHOR_TIMESTAMP_FREQ
> + *
> + * Note: these flags are exclusive to each other (only one can be
> used):
> + * - DRM_PANTHOR_TIMESTAMP_CPU_NONE
> + * - DRM_PANTHOR_TIMESTAMP_CPU_MONOTONIC
> + * - DRM_PANTHOR_TIMESTAMP_CPU_MONOTONIC_RAW
Yes, looks good to me.
Best regards,
Liviu
> */
> __u32 flags;
>
--
====================
| I would like to |
| fix the world, |
| but they're not |
| giving me the |
\ source code! /
---------------
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