[PATCH] drm/panthor: add gpu_load debugfs node
From: Guangliu Ding
Date: Tue Jul 07 2026 - 23:19:34 EST
Expose GPU utilization via /sys/kernel/debug/dri/<N>/gpu_load. The
file reports busy_time_ns, idle_time_ns and gpu_load %.
Values are snapshotted at the end of each devfreq sampling window
(~50 ms) rather than read from live accumulators, avoiding load swings
over short observation intervals.
The snapshot is cleared on suspend to avoid stale data when the GPU
is powered off.
Signed-off-by: Guangliu Ding <guangliu.ding@xxxxxxx>
---
Add /sys/kernel/debug/dri/<N>/gpu_load to expose GPU utilisation
from the last devfreq sampling window (~50 ms).
The file reports busy_time_ns, idle_time_ns and load percentage.
Tested on NXP i.MX95 EVK (Mali-G310 V2).
---
drivers/gpu/drm/panthor/panthor_devfreq.c | 80 +++++++++++++++++++++++++++++++
drivers/gpu/drm/panthor/panthor_devfreq.h | 6 +++
drivers/gpu/drm/panthor/panthor_drv.c | 2 +
3 files changed, 88 insertions(+)
diff --git a/drivers/gpu/drm/panthor/panthor_devfreq.c b/drivers/gpu/drm/panthor/panthor_devfreq.c
index 2249b41ca4af..1b3f58ddfbd3 100644
--- a/drivers/gpu/drm/panthor/panthor_devfreq.c
+++ b/drivers/gpu/drm/panthor/panthor_devfreq.c
@@ -1,12 +1,16 @@
// SPDX-License-Identifier: GPL-2.0 or MIT
/* Copyright 2019 Collabora ltd. */
+/* Copyright 2026 NXP */
#include <linux/clk.h>
+#include <linux/debugfs.h>
#include <linux/devfreq.h>
#include <linux/devfreq_cooling.h>
+#include <linux/math64.h>
#include <linux/platform_device.h>
#include <linux/pm_opp.h>
+#include <drm/drm_file.h>
#include <drm/drm_managed.h>
#include <drm/drm_print.h>
@@ -43,6 +47,22 @@ struct panthor_devfreq {
* and panthor_devfreq_record_{busy,idle}().
*/
spinlock_t lock;
+
+#ifdef CONFIG_DEBUG_FS
+ /**
+ * @last_busy_ns: Busy time in nanoseconds of the last completed devfreq window.
+ * Updated by panthor_devfreq_get_dev_status() before resetting the counters.
+ * Protected by @lock.
+ */
+ u64 last_busy_ns;
+
+ /**
+ * @last_total_ns: Total time in nanoseconds of the last completed devfreq window.
+ * Updated by panthor_devfreq_get_dev_status() before resetting the counters.
+ * Protected by @lock.
+ */
+ u64 last_total_ns;
+#endif
};
static void panthor_devfreq_update_utilization(struct panthor_devfreq *pdevfreq)
@@ -101,6 +121,11 @@ static int panthor_devfreq_get_dev_status(struct device *dev,
status->busy_time = ktime_to_ns(pdevfreq->busy_time);
+#ifdef CONFIG_DEBUG_FS
+ pdevfreq->last_busy_ns = status->busy_time;
+ pdevfreq->last_total_ns = status->total_time;
+#endif
+
panthor_devfreq_reset(pdevfreq);
spin_unlock_irqrestore(&pdevfreq->lock, irqflags);
@@ -283,6 +308,17 @@ void panthor_devfreq_suspend(struct panthor_device *ptdev)
return;
drm_WARN_ON(&ptdev->base, devfreq_suspend_device(pdevfreq->devfreq));
+
+#ifdef CONFIG_DEBUG_FS
+ {
+ unsigned long irqflags;
+
+ spin_lock_irqsave(&pdevfreq->lock, irqflags);
+ pdevfreq->last_busy_ns = 0;
+ pdevfreq->last_total_ns = 0;
+ spin_unlock_irqrestore(&pdevfreq->lock, irqflags);
+ }
+#endif
}
void panthor_devfreq_record_busy(struct panthor_device *ptdev)
@@ -332,3 +368,47 @@ unsigned long panthor_devfreq_get_freq(struct panthor_device *ptdev)
return freq;
}
+
+#ifdef CONFIG_DEBUG_FS
+static int panthor_devfreq_gpu_load_show(struct seq_file *m, void *unused)
+{
+ struct panthor_device *ptdev = m->private;
+ struct panthor_devfreq *pdevfreq = ptdev->devfreq;
+ unsigned long irqflags;
+ unsigned int gpu_load;
+ u64 total_ns;
+ u64 busy_ns;
+
+ if (!pdevfreq->devfreq) {
+ seq_puts(m, "devfreq not initialized\n");
+ return 0;
+ }
+
+ spin_lock_irqsave(&pdevfreq->lock, irqflags);
+ busy_ns = pdevfreq->last_busy_ns;
+ total_ns = pdevfreq->last_total_ns;
+ spin_unlock_irqrestore(&pdevfreq->lock, irqflags);
+
+ busy_ns = min(busy_ns, total_ns);
+ gpu_load = total_ns ? (unsigned int)div64_u64(busy_ns * 100ULL, total_ns) : 0;
+
+ seq_printf(m, "busy_time_ns: %llu idle_time_ns: %llu gpu_load: %u%%\n",
+ busy_ns, total_ns - busy_ns, gpu_load);
+
+ return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(panthor_devfreq_gpu_load);
+
+/**
+ * panthor_devfreq_debugfs_init() - Initialize devfreq debugfs entries
+ * @minor: DRM minor.
+ */
+void panthor_devfreq_debugfs_init(struct drm_minor *minor)
+{
+ struct panthor_device *ptdev = container_of(minor->dev,
+ struct panthor_device, base);
+
+ debugfs_create_file("gpu_load", 0444, minor->debugfs_root, ptdev,
+ &panthor_devfreq_gpu_load_fops);
+}
+#endif /* CONFIG_DEBUG_FS */
diff --git a/drivers/gpu/drm/panthor/panthor_devfreq.h b/drivers/gpu/drm/panthor/panthor_devfreq.h
index f8e29e02f66c..4552569abfe4 100644
--- a/drivers/gpu/drm/panthor/panthor_devfreq.h
+++ b/drivers/gpu/drm/panthor/panthor_devfreq.h
@@ -1,5 +1,6 @@
/* SPDX-License-Identifier: GPL-2.0 or MIT */
/* Copyright 2019 Collabora ltd. */
+/* Copyright 2026 NXP */
#ifndef __PANTHOR_DEVFREQ_H__
#define __PANTHOR_DEVFREQ_H__
@@ -20,4 +21,9 @@ void panthor_devfreq_record_idle(struct panthor_device *ptdev);
unsigned long panthor_devfreq_get_freq(struct panthor_device *ptdev);
+#ifdef CONFIG_DEBUG_FS
+struct drm_minor;
+void panthor_devfreq_debugfs_init(struct drm_minor *minor);
+#endif
+
#endif /* __PANTHOR_DEVFREQ_H__ */
diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
index e8dc4096c1d2..4093a6d21337 100644
--- a/drivers/gpu/drm/panthor/panthor_drv.c
+++ b/drivers/gpu/drm/panthor/panthor_drv.c
@@ -2,6 +2,7 @@
/* Copyright 2018 Marty E. Plummer <hanetzer@xxxxxxxxxxxxx> */
/* Copyright 2019 Linaro, Ltd., Rob Herring <robh@xxxxxxxxxx> */
/* Copyright 2019 Collabora ltd. */
+/* Copyright 2026 NXP */
#ifdef CONFIG_ARM_ARCH_TIMER
#include <asm/arch_timer.h>
@@ -1761,6 +1762,7 @@ static void panthor_debugfs_init(struct drm_minor *minor)
{
panthor_mmu_debugfs_init(minor);
panthor_gem_debugfs_init(minor);
+ panthor_devfreq_debugfs_init(minor);
}
#endif
---
base-commit: 8cdeaa50eae8dad34885515f62559ee83e7e8dda
change-id: 20260706-master-bd0eef99ca8e
Best regards,
--
Guangliu Ding <guangliu.ding@xxxxxxx>