Hello Chia-I,
On 16/09/2025 21:07, Chia-I Wu wrote:
> DRM_PANTHOR_DEV_QUERY_CALIBRATED_TIMESTAMP_INFO provides a way to query
> and calibrate CPU and GPU timestamps.
>
> This is needed because CPU and GPU timestamps are captured separately.
> The implementation makes an effort to minimize the capture duration,
> which is crucial for calibration and not exactly feasible from
> userspace.
>
> Signed-off-by: Chia-I Wu <[email protected]>
>
> ---
> The query is inspired by xe's DRM_XE_DEVICE_QUERY_ENGINE_CYCLES and the
> naming is inspired by VK_KHR_calibrated_timestamps. The userspace change
> is https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37424.
> ---
> drivers/gpu/drm/panthor/panthor_drv.c | 88 ++++++++++++++++++++++++++-
> include/uapi/drm/panthor_drm.h | 31 ++++++++++
> 2 files changed, 118 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/panthor/panthor_drv.c
> b/drivers/gpu/drm/panthor/panthor_drv.c
> index fdbe89ef7f43c..06da6dcf016ef 100644
> --- a/drivers/gpu/drm/panthor/panthor_drv.c
> +++ b/drivers/gpu/drm/panthor/panthor_drv.c
> @@ -13,6 +13,7 @@
> #include <linux/pagemap.h>
> #include <linux/platform_device.h>
> #include <linux/pm_runtime.h>
> +#include <linux/sched/clock.h>
> #include <linux/time64.h>
>
> #include <drm/drm_auth.h>
> @@ -172,6 +173,7 @@ panthor_get_uobj_array(const struct drm_panthor_obj_array
> *in, u32 min_stride,
> PANTHOR_UOBJ_DECL(struct drm_panthor_csif_info, pad), \
> PANTHOR_UOBJ_DECL(struct drm_panthor_timestamp_info,
> current_timestamp), \
> PANTHOR_UOBJ_DECL(struct drm_panthor_group_priorities_info,
> pad), \
> + PANTHOR_UOBJ_DECL(struct
> drm_panthor_calibrated_timestamp_info, gpu_timestamp), \
> PANTHOR_UOBJ_DECL(struct drm_panthor_sync_op, timeline_value),
> \
> PANTHOR_UOBJ_DECL(struct drm_panthor_queue_submit, syncs), \
> PANTHOR_UOBJ_DECL(struct drm_panthor_queue_create,
> ringbuf_size), \
> @@ -779,6 +781,74 @@ static int panthor_query_timestamp_info(struct
> panthor_device *ptdev,
> return 0;
> }
>
> +static int panthor_query_calibrated_timestamp_info(
> + struct panthor_device *ptdev, const struct
> drm_panthor_calibrated_timestamp_info __user *in,
> + u32 in_size, struct drm_panthor_calibrated_timestamp_info *out)
> +{
> + /* cpu_clockid and pad take up the first 8 bytes */
> + const u32 min_size = 8;
> + u64 (*cpu_timestamp)(void);
> + int ret;
> +
> + if (in_size < min_size)
> + return -EINVAL;
> + if (!access_ok(in, min_size))
> + return -EFAULT;
> + ret = __get_user(out->cpu_clockid, &in->cpu_clockid);
> + if (ret)
> + return ret;
> + ret = __get_user(out->pad, &in->pad);
> + if (ret)
> + return ret;
> +
> + switch (out->cpu_clockid) {
> + case CLOCK_MONOTONIC:
> + cpu_timestamp = ktime_get_ns;
> + break;
> + case CLOCK_MONOTONIC_RAW:
> + cpu_timestamp = ktime_get_raw_ns;
> + break;
> + case CLOCK_REALTIME:
> + cpu_timestamp = ktime_get_real_ns;
> + break;
> + case CLOCK_BOOTTIME:
> + cpu_timestamp = ktime_get_boottime_ns;
> + break;
> + case CLOCK_TAI:
> + cpu_timestamp = ktime_get_clocktai_ns;
> + break;
Out of interest, what is the use-case for the REALTIME, BOOTTIME and TAI
clocks? Looking at
VK_KHR_calibrated_timestamps, it seems that only MONOTONIC and MONOTONIC_RAW
are exposed directly.
I worry that providing the other clocks may make it easier for accidentally
querying timestamps that
can't be correlated with driver state. A recent Mesa change aligned PanVK
Perfetto instrumentation on
MONOTONIC_RAW [1], and the performance counter patches I've proposed also use
MONOTONIC_RAW
as the only clock source.
> + default:
> + return -EINVAL;
> + }
> +
> + if (out->pad)
> + return -EINVAL;
> +
> + ret = panthor_device_resume_and_get(ptdev);
> + if (ret)
> + return ret;
> +
> + do {
> + const u32 hi = gpu_read(ptdev, GPU_TIMESTAMP + 4);
> +
> + /* keep duration minimal */
> + preempt_disable();
> + out->duration = local_clock();
> + out->cpu_timestamp = cpu_timestamp();
> + out->gpu_timestamp = gpu_read(ptdev, GPU_TIMESTAMP);
> + out->duration = local_clock() - out->duration;
> + preempt_enable();
> +
> + if (likely(hi == gpu_read(ptdev, GPU_TIMESTAMP + 4))) {
> + out->gpu_timestamp |= (u64)hi << 32;
> + break;
> + }
> + } while (true);
> +
> + pm_runtime_put(ptdev->base.dev);
> + return 0;
> +}
> +
> static int group_priority_permit(struct drm_file *file,
> u8 priority)
> {
> @@ -815,6 +885,7 @@ static int panthor_ioctl_dev_query(struct drm_device
> *ddev, void *data, struct d
> struct drm_panthor_dev_query *args = data;
> struct drm_panthor_timestamp_info timestamp_info;
> struct drm_panthor_group_priorities_info priorities_info;
> + struct drm_panthor_calibrated_timestamp_info calibrated_timestamp_info;
> int ret;
>
> if (!args->pointer) {
> @@ -835,6 +906,10 @@ static int panthor_ioctl_dev_query(struct drm_device
> *ddev, void *data, struct d
> args->size = sizeof(priorities_info);
> return 0;
>
> + case DRM_PANTHOR_DEV_QUERY_CALIBRATED_TIMESTAMP_INFO:
> + args->size = sizeof(calibrated_timestamp_info);
> + return 0;
> +
> default:
> return -EINVAL;
> }
> @@ -859,6 +934,16 @@ static int panthor_ioctl_dev_query(struct drm_device
> *ddev, void *data, struct d
> panthor_query_group_priorities_info(file, &priorities_info);
> return PANTHOR_UOBJ_SET(args->pointer, args->size,
> priorities_info);
>
> + case DRM_PANTHOR_DEV_QUERY_CALIBRATED_TIMESTAMP_INFO: {
> + ret = panthor_query_calibrated_timestamp_info(ptdev,
> u64_to_user_ptr(args->pointer),
> + args->size,
> +
> &calibrated_timestamp_info);
> + if (ret)
> + return ret;
> +
> + return PANTHOR_UOBJ_SET(args->pointer, args->size,
> calibrated_timestamp_info);
> + }
> +
> default:
> return -EINVAL;
> }
> @@ -1601,6 +1686,7 @@ static void panthor_debugfs_init(struct drm_minor
> *minor)
> * - 1.3 - adds DRM_PANTHOR_GROUP_STATE_INNOCENT flag
> * - 1.4 - adds DRM_IOCTL_PANTHOR_BO_SET_LABEL ioctl
> * - 1.5 - adds DRM_PANTHOR_SET_USER_MMIO_OFFSET ioctl
> + * - 1.6 - adds DRM_PANTHOR_DEV_QUERY_CALIBRATED_TIMESTAMP_INFO query
> */
> static const struct drm_driver panthor_drm_driver = {
> .driver_features = DRIVER_RENDER | DRIVER_GEM | DRIVER_SYNCOBJ |
> @@ -1614,7 +1700,7 @@ static const struct drm_driver panthor_drm_driver = {
> .name = "panthor",
> .desc = "Panthor DRM driver",
> .major = 1,
> - .minor = 5,
> + .minor = 6,
>
> .gem_create_object = panthor_gem_create_object,
> .gem_prime_import_sg_table = drm_gem_shmem_prime_import_sg_table,
> diff --git a/include/uapi/drm/panthor_drm.h b/include/uapi/drm/panthor_drm.h
> index 467d365ed7ba7..7f3ff43f17952 100644
> --- a/include/uapi/drm/panthor_drm.h
> +++ b/include/uapi/drm/panthor_drm.h
> @@ -243,6 +243,11 @@ enum drm_panthor_dev_query_type {
> * @DRM_PANTHOR_DEV_QUERY_GROUP_PRIORITIES_INFO: Query allowed group
> priorities information.
> */
> DRM_PANTHOR_DEV_QUERY_GROUP_PRIORITIES_INFO,
> +
> + /** @DRM_PANTHOR_DEV_QUERY_CALIBRATED_TIMESTAMP_INFO: Query calibrated
> + * timestamp information.
> + */
> + DRM_PANTHOR_DEV_QUERY_CALIBRATED_TIMESTAMP_INFO,
> };
>
> /**
> @@ -402,6 +407,32 @@ struct drm_panthor_group_priorities_info {
> __u8 pad[3];
> };
>
> +/**
> + * struct drm_panthor_calibrated_timestamp_info - Calibrated timestamp
> information
> + *
> + * Structure grouping all queryable information relating to the calibrated
> timestamp.
> + */
> +struct drm_panthor_calibrated_timestamp_info {
> + /** @clockid: The CPU clock id.
> + *
> + * Must be one of CLOCK_MONOTONIC, CLOCK_MONOTONIC_RAW,
> + * CLOCK_REALTIME, CLOCK_BOOTTIME, or CLOCK_TAI.
> + */
> + __s32 cpu_clockid;
> +
> + /** @pad: MBZ. */
> + __u32 pad;
> +
> + /** @duration: Duration for querying all timestamps in nanoseconds. */
> + __u64 duration;
> +
> + /** @cpu_timestamp: The current CPU timestamp in nanoseconds. */
> + __u64 cpu_timestamp;
> +
> + /** @gpu_timestamp: The current GPU timestamp in cycles. */
> + __u64 gpu_timestamp;
> +};
> +
> /**
> * struct drm_panthor_dev_query - Arguments passed to
> DRM_PANTHOR_IOCTL_DEV_QUERY
> */
Kind regards,
Lukas
[1]: https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34390
