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

drivers/gpu/drm/panthor/panthor_drv.c

@@ -3,6 +3,10 @@
 /* Copyright 2019 Linaro, Ltd., Rob Herring <robh@kernel.org> */
 /* Copyright 2019 Collabora ltd. */
 
+#ifdef CONFIG_ARM_ARCH_TIMER
+#include <asm/arch_timer.h>
+#endif
+
 #include <linux/list.h>
 #include <linux/module.h>
 #include <linux/of_platform.h>
@@ -164,6 +168,7 @@ panthor_get_uobj_array(const struct drm_panthor_obj_array *in, u32 min_stride,
 	_Generic(_obj_name, \
 		 PANTHOR_UOBJ_DECL(struct drm_panthor_gpu_info, tiler_present), \
 		 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_sync_op, timeline_value), \
 		 PANTHOR_UOBJ_DECL(struct drm_panthor_queue_submit, syncs), \
 		 PANTHOR_UOBJ_DECL(struct drm_panthor_queue_create, ringbuf_size), \
@@ -750,10 +755,33 @@ static void panthor_submit_ctx_cleanup(struct panthor_submit_ctx *ctx,
 	kvfree(ctx->jobs);
 }
 
+static int panthor_query_timestamp_info(struct panthor_device *ptdev,
+					struct drm_panthor_timestamp_info *arg)
+{
+	int ret;
+
+	ret = pm_runtime_resume_and_get(ptdev->base.dev);
+	if (ret)
+		return ret;
+
+#ifdef CONFIG_ARM_ARCH_TIMER
+	arg->timestamp_frequency = arch_timer_get_cntfrq();
+#else
+	arg->timestamp_frequency = 0;
+#endif
+	arg->current_timestamp = panthor_gpu_read_timestamp(ptdev);
+	arg->timestamp_offset = panthor_gpu_read_timestamp_offset(ptdev);
+
+	pm_runtime_put(ptdev->base.dev);
+	return 0;
+}
+
 static int panthor_ioctl_dev_query(struct drm_device *ddev, void *data, struct drm_file *file)
 {
 	struct panthor_device *ptdev = container_of(ddev, struct panthor_device, base);
 	struct drm_panthor_dev_query *args = data;
+	struct drm_panthor_timestamp_info timestamp_info;
+	int ret;
 
 	if (!args->pointer) {
 		switch (args->type) {
@@ -765,6 +793,10 @@ static int panthor_ioctl_dev_query(struct drm_device *ddev, void *data, struct d
 			args->size = sizeof(ptdev->csif_info);
 			return 0;
 
+		case DRM_PANTHOR_DEV_QUERY_TIMESTAMP_INFO:
+			args->size = sizeof(timestamp_info);
+			return 0;
+
 		default:
 			return -EINVAL;
 		}
@@ -777,6 +809,14 @@ static int panthor_ioctl_dev_query(struct drm_device *ddev, void *data, struct d
 	case DRM_PANTHOR_DEV_QUERY_CSIF_INFO:
 		return PANTHOR_UOBJ_SET(args->pointer, args->size, ptdev->csif_info);
 
+	case DRM_PANTHOR_DEV_QUERY_TIMESTAMP_INFO:
+		ret = panthor_query_timestamp_info(ptdev, &timestamp_info);
+
+		if (ret)
+			return ret;
+
+		return PANTHOR_UOBJ_SET(args->pointer, args->size, timestamp_info);
+
 	default:
 		return -EINVAL;
 	}
@@ -1387,6 +1427,7 @@ static const struct file_operations panthor_drm_driver_fops = {
 /*
  * PanCSF driver version:
  * - 1.0 - initial interface
+ * - 1.1 - adds DEV_QUERY_TIMESTAMP_INFO query
  */
 static const struct drm_driver panthor_drm_driver = {
 	.driver_features = DRIVER_RENDER | DRIVER_GEM | DRIVER_SYNCOBJ |
@@ -1400,7 +1441,7 @@ static const struct drm_driver panthor_drm_driver = {
 	.desc = "Panthor DRM driver",
 	.date = "20230801",
 	.major = 1,
-	.minor = 0,
+	.minor = 1,
 
 	.gem_create_object = panthor_gem_create_object,
 	.gem_prime_import_sg_table = drm_gem_shmem_prime_import_sg_table,

drivers/gpu/drm/panthor/panthor_gpu.c

@@ -480,3 +480,50 @@ void panthor_gpu_resume(struct panthor_device *ptdev)
 	panthor_gpu_irq_resume(&ptdev->gpu->irq, GPU_INTERRUPTS_MASK);
 	panthor_gpu_l2_power_on(ptdev);
 }
+
+/**
+ * panthor_gpu_read_64bit_counter() - Read a 64-bit counter at a given offset.
+ * @ptdev: Device.
+ * @reg: The offset of the register to read.
+ *
+ * Return: The counter value.
+ */
+static u64
+panthor_gpu_read_64bit_counter(struct panthor_device *ptdev, u32 reg)
+{
+	u32 hi, lo;
+
+	do {
+		hi = gpu_read(ptdev, reg + 0x4);
+		lo = gpu_read(ptdev, reg);
+	} while (hi != gpu_read(ptdev, reg + 0x4));
+
+	return ((u64)hi << 32) | lo;
+}
+
+/**
+ * panthor_gpu_read_timestamp() - Read the timestamp register.
+ * @ptdev: Device.
+ *
+ * Return: The GPU timestamp value.
+ */
+u64 panthor_gpu_read_timestamp(struct panthor_device *ptdev)
+{
+	return panthor_gpu_read_64bit_counter(ptdev, GPU_TIMESTAMP_LO);
+}
+
+/**
+ * panthor_gpu_read_timestamp_offset() - Read the timestamp offset register.
+ * @ptdev: Device.
+ *
+ * Return: The GPU timestamp offset value.
+ */
+u64 panthor_gpu_read_timestamp_offset(struct panthor_device *ptdev)
+{
+	u32 hi, lo;
+
+	hi = gpu_read(ptdev, GPU_TIMESTAMP_OFFSET_HI);
+	lo = gpu_read(ptdev, GPU_TIMESTAMP_OFFSET_LO);
+
+	return ((u64)hi << 32) | lo;
+}

drivers/gpu/drm/panthor/panthor_gpu.h

@@ -5,6 +5,8 @@
 #ifndef __PANTHOR_GPU_H__
 #define __PANTHOR_GPU_H__
 
+#include <linux/types.h>
+
 struct panthor_device;
 
 int panthor_gpu_init(struct panthor_device *ptdev);
@@ -48,5 +50,7 @@ int panthor_gpu_l2_power_on(struct panthor_device *ptdev);
 int panthor_gpu_flush_caches(struct panthor_device *ptdev,
 			     u32 l2, u32 lsc, u32 other);
 int panthor_gpu_soft_reset(struct panthor_device *ptdev);
+u64 panthor_gpu_read_timestamp(struct panthor_device *ptdev);
+u64 panthor_gpu_read_timestamp_offset(struct panthor_device *ptdev);
 
 #endif

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
  */