linux-kernel - Re: [PATCH v10 3/4] drm/panthor: Add tracepoint for hardware utilisation changes

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Message-ID: <aXLyzd6pMmexwWlY@laps>
Date: Thu, 22 Jan 2026 23:02:21 -0500
From: Sasha Levin <sashal@...nel.org>
To: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
Cc: 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>,
	Chia-I Wu <olvaffe@...il.com>,
	Karunika Choo <karunika.choo@....com>, kernel@...labora.com,
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v10 3/4] drm/panthor: Add tracepoint for hardware
 utilisation changes

Hi Nicolas,

On Fri, Jan 16, 2026 at 01:57:32PM +0100, Nicolas Frattaroli wrote:
>Mali GPUs have three registers that indicate which parts of the hardware
>are powered at any moment. These take the form of bitmaps. In the case
>of SHADER_READY for example, a high bit indicates that the shader core
>corresponding to that bit index is powered on. 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 _READY registers will contain new interesting data. During
>power transitions, the GPU_IRQ_POWER_CHANGED interrupt will fire, and
>the registers will likewise contain potentially changed data.
>
>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
>_READY registers and corresponding interrupts are already available in
>v9 and onwards.
>
>Expose the data 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 powered shader core, measuring when hardware
>is allowed to go to a powered off state again, and so on.
>
>The registration/unregistration functions for the tracepoint go through
>a wrapper in panthor_hw.c, so that v14+ can implement the same
>tracepoint by adding its hardware specific IRQ on/off callbacks to the
>panthor_hw.ops member.
>
>Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
>---
> drivers/gpu/drm/panthor/panthor_gpu.c   | 28 +++++++++++++++
> drivers/gpu/drm/panthor/panthor_gpu.h   |  2 ++
> drivers/gpu/drm/panthor/panthor_hw.c    | 62 +++++++++++++++++++++++++++++++++
> drivers/gpu/drm/panthor/panthor_hw.h    |  8 +++++
> drivers/gpu/drm/panthor/panthor_trace.h | 58 ++++++++++++++++++++++++++++++
> 5 files changed, 158 insertions(+)
>
>diff --git a/drivers/gpu/drm/panthor/panthor_gpu.c b/drivers/gpu/drm/panthor/panthor_gpu.c
>index 9304469a711a..2ab444ee8c71 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"

With this commit, I'm seeing:

In file included from drivers/gpu/drm/panthor/panthor_trace.h:86,
                  from drivers/gpu/drm/panthor/panthor_gpu.c:26:
./include/trace/define_trace.h:118:42: fatal error: ./panthor_trace.h: No such file or directory
   118 | #include TRACE_INCLUDE(TRACE_INCLUDE_FILE)

I think we need to add in 'CFLAGS_panthor_gpu.o := -I$(src)' to the Makefile
too, but I haven't tested that yet.

-- 
Thanks,
Sasha