drm/panthor: Add DEV_QUERY_TIMESTAMP_INFO dev query

Expose timestamp information supported by the GPU with a new device
query.

Mali uses an external timer as GPU system time. On ARM, this is wired to
the generic arch timer so we wire cntfrq_el0 as device frequency.

This new uAPI will be used in Mesa to implement timestamp queries and
VK_KHR_calibrated_timestamps.

Since this extends the uAPI and because userland needs a way to advertise
those features conditionally, this also bumps the driver minor version.

v2:
- Rewrote to use GPU timestamp register
- Added timestamp_offset to drm_panthor_timestamp_info
- Add missing include for arch_timer_get_cntfrq
- Rework commit message

v3:
- Add panthor_gpu_read_64bit_counter
- Change panthor_gpu_read_timestamp to use
  panthor_gpu_read_64bit_counter

v4:
- Fix multiple typos in uAPI documentation
- Mention behavior when the timestamp frequency is unknown
- Use u64 instead of unsigned long long
  for panthor_gpu_read_timestamp
- Apply r-b from Mihail

Signed-off-by: Mary Guillemard <mary.guillemard@collabora.com>
Reviewed-by: Mihail Atanassov <mihail.atanassov@arm.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240830080349.24736-2-mary.guillemard@collabora.com

include/uapi/drm/panthor_drm.h

@@ -260,6 +260,9 @@ enum drm_panthor_dev_query_type {
 
 	/** @DRM_PANTHOR_DEV_QUERY_CSIF_INFO: Query command-stream interface information. */
 	DRM_PANTHOR_DEV_QUERY_CSIF_INFO,
+
+	/** @DRM_PANTHOR_DEV_QUERY_TIMESTAMP_INFO: Query timestamp information. */
+	DRM_PANTHOR_DEV_QUERY_TIMESTAMP_INFO,
 };
 
 /**
@@ -377,6 +380,25 @@ struct drm_panthor_csif_info {
 	__u32 pad;
 };
 
+/**
+ * struct drm_panthor_timestamp_info - Timestamp information
+ *
+ * Structure grouping all queryable information relating to the GPU timestamp.
+ */
+struct drm_panthor_timestamp_info {
+	/**
+	 * @timestamp_frequency: The frequency of the timestamp timer or 0 if
+	 * unknown.
+	 */
+	__u64 timestamp_frequency;
+
+	/** @current_timestamp: The current timestamp. */
+	__u64 current_timestamp;
+
+	/** @timestamp_offset: The offset of the timestamp timer. */
+	__u64 timestamp_offset;
+};
+
 /**
  * struct drm_panthor_dev_query - Arguments passed to DRM_PANTHOR_IOCTL_DEV_QUERY
  */