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Message-ID: <4363e055-c1f9-49c6-81dd-c2e5f8307310@arm.com>
Date: Mon, 8 Dec 2025 17:14:53 +0000
From: Karunika Choo <karunika.choo@....com>
To: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>,
Boris Brezillon <boris.brezillon@...labora.com>,
Steven Price <steven.price@....com>, Liviu Dudau <liviu.dudau@....com>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Cc: kernel@...labora.com, linux-kernel@...r.kernel.org,
dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 1/2] drm/panthor: Add tracepoint for hardware utilisation
changes
On 03/12/2025 13:56, Nicolas Frattaroli wrote:
> Mali GPUs have three registers that indicate which parts of the hardware
> are powered and active at any moment. These take the form of bitmaps. In
> the case of SHADER_PWRACTIVE for example, a high bit indicates that the
> shader core corresponding to that bit index is active. These bitmaps
> aren't solely contiguous bits, as it's common to have holes in the
> sequence of shader core indices, and the actual set of which cores are
> present is defined by the "shader present" register.
>
> When the GPU finishes a power state transition, it fires a
> GPU_IRQ_POWER_CHANGED_ALL interrupt. After such an interrupt is
> received, the PWRACTIVE registers will likely contain interesting new
> information.
>
> This is not to be confused with the PWR_IRQ_POWER_CHANGED_ALL interrupt,
> which is something related to Mali v14+'s power control logic. The
> PWRACTIVE registers and corresponding interrupts are already available
> in v9 and onwards.
>
> Expose this as a tracepoint to userspace. This allows users to debug
> various scenarios and gather interesting information, such as: knowing
> how much hardware is lit up at any given time, correlating graphics
> corruption with a specific active shader core, measuring when hardware
> is allowed to go to an inactive state again, and so on.
>
> Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
> ---
> drivers/gpu/drm/panthor/panthor_device.c | 1 +
> drivers/gpu/drm/panthor/panthor_gpu.c | 9 ++++++++
> drivers/gpu/drm/panthor/panthor_trace.h | 38 ++++++++++++++++++++++++++++++++
> 3 files changed, 48 insertions(+)
>
> diff --git a/drivers/gpu/drm/panthor/panthor_device.c b/drivers/gpu/drm/panthor/panthor_device.c
> index e133b1e0ad6d..a3cb934104b8 100644
> --- a/drivers/gpu/drm/panthor/panthor_device.c
> +++ b/drivers/gpu/drm/panthor/panthor_device.c
> @@ -548,6 +548,7 @@ int panthor_device_resume(struct device *dev)
> DRM_PANTHOR_USER_MMIO_OFFSET, 0, 1);
> atomic_set(&ptdev->pm.state, PANTHOR_DEVICE_PM_STATE_ACTIVE);
> mutex_unlock(&ptdev->pm.mmio_lock);
> +
> return 0;
>
> err_suspend_devfreq:
> diff --git a/drivers/gpu/drm/panthor/panthor_gpu.c b/drivers/gpu/drm/panthor/panthor_gpu.c
> index 9cb5dee93212..8830aa9a5c4b 100644
> --- a/drivers/gpu/drm/panthor/panthor_gpu.c
> +++ b/drivers/gpu/drm/panthor/panthor_gpu.c
> @@ -22,6 +22,9 @@
> #include "panthor_hw.h"
> #include "panthor_regs.h"
>
> +#define CREATE_TRACE_POINTS
> +#include "panthor_trace.h"
> +
> /**
> * struct panthor_gpu - GPU block management data.
> */
> @@ -46,6 +49,7 @@ struct panthor_gpu {
> (GPU_IRQ_FAULT | \
> GPU_IRQ_PROTM_FAULT | \
> GPU_IRQ_RESET_COMPLETED | \
> + GPU_IRQ_POWER_CHANGED_ALL | \
> GPU_IRQ_CLEAN_CACHES_COMPLETED)
>
> static void panthor_gpu_coherency_set(struct panthor_device *ptdev)
> @@ -97,6 +101,11 @@ static void panthor_gpu_irq_handler(struct panthor_device *ptdev, u32 status)
> wake_up_all(&ptdev->gpu->reqs_acked);
> }
> spin_unlock(&ptdev->gpu->reqs_lock);
> +
> + if (status & GPU_IRQ_POWER_CHANGED_ALL)
> + trace_gpu_power_active(gpu_read64(ptdev, SHADER_PWRACTIVE),
> + gpu_read64(ptdev, TILER_PWRACTIVE),
> + gpu_read64(ptdev, L2_PWRACTIVE));
> }
> PANTHOR_IRQ_HANDLER(gpu, GPU, panthor_gpu_irq_handler);
>
> diff --git a/drivers/gpu/drm/panthor/panthor_trace.h b/drivers/gpu/drm/panthor/panthor_trace.h
> new file mode 100644
> index 000000000000..01013f81e68a
> --- /dev/null
> +++ b/drivers/gpu/drm/panthor/panthor_trace.h
> @@ -0,0 +1,38 @@
> +/* SPDX-License-Identifier: GPL-2.0 or MIT */
> +/* Copyright 2025 Collabora ltd. */
> +
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM panthor
> +
> +#if !defined(__PANTHOR_TRACE_H__) || defined(TRACE_HEADER_MULTI_READ)
> +#define __PANTHOR_TRACE_H__
> +
> +#include <linux/tracepoint.h>
> +#include <linux/types.h>
> +
> +TRACE_EVENT(gpu_power_active,
> + TP_PROTO(u64 shader_bitmap, u64 tiler_bitmap, u64 l2_bitmap),
nit: if you want to add tracing can we also add the device name as
well? Something like:
TP_PROTO(struct device *dev, ...),
TP_ARGS(dev, ...),
TP_STRUCT__ENTRY(
__string(dev_name, dev_name(dev))
...
).
...
This will help differentiate the device it is originating from in
a multi GPU situation.
Kind regards,
Karunika
> + TP_ARGS(shader_bitmap, tiler_bitmap, l2_bitmap),
> + TP_STRUCT__entry(
> + __field(u64, shader_bitmap)
> + __field(u64, tiler_bitmap)
> + __field(u64, l2_bitmap)
> + ),
> + TP_fast_assign(
> + __entry->shader_bitmap = shader_bitmap;
> + __entry->tiler_bitmap = tiler_bitmap;
> + __entry->l2_bitmap = l2_bitmap;
> + ),
> + TP_printk("shader_bitmap=0x%llx tiler_bitmap=0x%llx l2_bitmap=0x%llx",
> + __entry->shader_bitmap, __entry->tiler_bitmap, __entry->l2_bitmap
> + )
> +);
> +
> +#endif /* __PANTHOR_TRACE_H__ */
> +
> +#undef TRACE_INCLUDE_PATH
> +#define TRACE_INCLUDE_PATH .
> +#undef TRACE_INCLUDE_FILE
> +#define TRACE_INCLUDE_FILE panthor_trace
> +
> +#include <trace/define_trace.h>
>
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