On 11/12/2025 16:15, 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 <[email protected]>
> ---
> drivers/gpu/drm/panthor/panthor_gpu.c | 38 ++++++++++++++++++--
> 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 | 59 +++++++++++++++++++++++++++++++
> 5 files changed, 167 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/panthor/panthor_gpu.c
> b/drivers/gpu/drm/panthor/panthor_gpu.c
> index 057e167468d0..67572b607b55 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.
> */
> @@ -29,6 +32,9 @@ struct panthor_gpu {
> /** @irq: GPU irq. */
> struct panthor_irq irq;
>
> + /** @irq_mask: GPU irq mask. */
> + u32 irq_mask;
> +
> /** @reqs_lock: Lock protecting access to pending_reqs. */
> spinlock_t reqs_lock;
>
> @@ -48,6 +54,9 @@ struct panthor_gpu {
> GPU_IRQ_RESET_COMPLETED | \
> GPU_IRQ_CLEAN_CACHES_COMPLETED)
>
> +#define GPU_POWER_INTERRUPTS_MASK \
> + (GPU_IRQ_POWER_CHANGED | GPU_IRQ_POWER_CHANGED_ALL)
> +
> static void panthor_gpu_coherency_set(struct panthor_device *ptdev)
> {
> gpu_write(ptdev, GPU_COHERENCY_PROTOCOL,
> @@ -80,6 +89,12 @@ static void panthor_gpu_irq_handler(struct panthor_device
> *ptdev, u32 status)
> {
> gpu_write(ptdev, GPU_INT_CLEAR, status);
>
> + if (tracepoint_enabled(gpu_power_status) && (status &
> GPU_POWER_INTERRUPTS_MASK))
> + trace_gpu_power_status(ptdev->base.dev,
> + gpu_read64(ptdev, SHADER_READY),
> + gpu_read64(ptdev, TILER_READY),
> + gpu_read64(ptdev, L2_READY));
> +
> if (status & GPU_IRQ_FAULT) {
> u32 fault_status = gpu_read(ptdev, GPU_FAULT_STATUS);
> u64 address = gpu_read64(ptdev, GPU_FAULT_ADDR);
> @@ -139,6 +154,7 @@ int panthor_gpu_init(struct panthor_device *ptdev)
> init_waitqueue_head(&gpu->reqs_acked);
> mutex_init(&gpu->cache_flush_lock);
> ptdev->gpu = gpu;
> + gpu->irq_mask = GPU_INTERRUPTS_MASK;
>
> dma_set_max_seg_size(ptdev->base.dev, UINT_MAX);
> pa_bits = GPU_MMU_FEATURES_PA_BITS(ptdev->gpu_info.mmu_features);
> @@ -150,13 +166,31 @@ int panthor_gpu_init(struct panthor_device *ptdev)
> if (irq < 0)
> return irq;
>
> - ret = panthor_request_gpu_irq(ptdev, &ptdev->gpu->irq, irq,
> GPU_INTERRUPTS_MASK);
> + ret = panthor_request_gpu_irq(ptdev, &ptdev->gpu->irq, irq,
> gpu->irq_mask);
> if (ret)
> return ret;
>
> return 0;
> }
>
> +int panthor_gpu_power_changed_on(struct panthor_device *ptdev)
> +{
> + guard(pm_runtime_active)(ptdev->base.dev);
> +
> + ptdev->gpu->irq_mask |= GPU_POWER_INTERRUPTS_MASK;
> + panthor_gpu_irq_mask_set(&ptdev->gpu->irq, ptdev->gpu->irq_mask);
> +
> + return 0;
> +}
> +
> +void panthor_gpu_power_changed_off(struct panthor_device *ptdev)
> +{
> + guard(pm_runtime_active)(ptdev->base.dev);
> +
> + ptdev->gpu->irq_mask &= ~GPU_POWER_INTERRUPTS_MASK;
> + panthor_gpu_irq_mask_set(&ptdev->gpu->irq, ptdev->gpu->irq_mask);
> +}
> +
> /**
> * panthor_gpu_block_power_off() - Power-off a specific block of the GPU
> * @ptdev: Device.
> @@ -395,7 +429,7 @@ void panthor_gpu_suspend(struct panthor_device *ptdev)
> */
> void panthor_gpu_resume(struct panthor_device *ptdev)
> {
> - panthor_gpu_irq_resume(&ptdev->gpu->irq, GPU_INTERRUPTS_MASK);
> + panthor_gpu_irq_resume(&ptdev->gpu->irq, ptdev->gpu->irq_mask);
> panthor_hw_l2_power_on(ptdev);
> }
>
> diff --git a/drivers/gpu/drm/panthor/panthor_gpu.h
> b/drivers/gpu/drm/panthor/panthor_gpu.h
> index 12e66f48ced1..12c263a39928 100644
> --- a/drivers/gpu/drm/panthor/panthor_gpu.h
> +++ b/drivers/gpu/drm/panthor/panthor_gpu.h
> @@ -51,5 +51,7 @@ 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);
> +void panthor_gpu_power_changed_off(struct panthor_device *ptdev);
> +int panthor_gpu_power_changed_on(struct panthor_device *ptdev);
>
> #endif
> diff --git a/drivers/gpu/drm/panthor/panthor_hw.c
> b/drivers/gpu/drm/panthor/panthor_hw.c
> index 87ebb7ae42c4..ae3320d0e251 100644
> --- a/drivers/gpu/drm/panthor/panthor_hw.c
> +++ b/drivers/gpu/drm/panthor/panthor_hw.c
> @@ -1,6 +1,8 @@
> // SPDX-License-Identifier: GPL-2.0 or MIT
> /* Copyright 2025 ARM Limited. All rights reserved. */
>
> +#include <linux/platform_device.h>
> +
> #include <drm/drm_print.h>
>
> #include "panthor_device.h"
> @@ -29,6 +31,8 @@ static struct panthor_hw panthor_hw_arch_v10 = {
> .soft_reset = panthor_gpu_soft_reset,
> .l2_power_off = panthor_gpu_l2_power_off,
> .l2_power_on = panthor_gpu_l2_power_on,
> + .power_changed_off = panthor_gpu_power_changed_off,
> + .power_changed_on = panthor_gpu_power_changed_on,
> },
> };
>
> @@ -53,6 +57,64 @@ static struct panthor_hw_entry panthor_hw_match[] = {
> },
> };
>
> +static int panthor_hw_set_power_tracing(struct device *dev, void *data)
> +{
> + struct panthor_device *ptdev = dev_get_drvdata(dev);
> +
> + if (!ptdev)
> + return -ENODEV;
> +
> + if (!ptdev->hw)
> + return 0;
> +
> + if (data) {
> + if (ptdev->hw->ops.power_changed_on)
> + return ptdev->hw->ops.power_changed_on(ptdev);
> + } else {
> + if (ptdev->hw->ops.power_changed_off)
> + ptdev->hw->ops.power_changed_off(ptdev);
> + }
> +
> + return 0;
> +}
> +
> +int panthor_hw_power_status_register(void)
> +{
> + struct device_driver *drv;
> + int ret;
> +
> + drv = driver_find("panthor", &platform_bus_type);
> + if (!drv)
> + return -ENODEV;
> +
> + ret = driver_for_each_device(drv, NULL, (void *)true,
> + panthor_hw_set_power_tracing);
> +
> + return ret;
> +}
> +
> +void panthor_hw_power_status_unregister(void)
> +{
> + struct device_driver *drv;
> + int ret;
> +
> + drv = driver_find("panthor", &platform_bus_type);
> + if (!drv)
> + return;
> +
> + ret = driver_for_each_device(drv, NULL, NULL,
> panthor_hw_set_power_tracing);
> +
> + /*
> + * Ideally, it'd be possible to ask driver_for_each_device to hand us
> + * another "start" to keep going after the failing device, but it
> + * doesn't do that. Minor inconvenience in what is probably a bad day
> + * on the computer already though.
> + */
> + if (ret)
> + pr_warn("Couldn't mask power IRQ for at least one device:
> %pe\n",
> + ERR_PTR(ret));
> +}
> +
> static char *get_gpu_model_name(struct panthor_device *ptdev)
> {
> const u32 gpu_id = ptdev->gpu_info.gpu_id;
> diff --git a/drivers/gpu/drm/panthor/panthor_hw.h
> b/drivers/gpu/drm/panthor/panthor_hw.h
> index 56c68c1e9c26..2c28aea82841 100644
> --- a/drivers/gpu/drm/panthor/panthor_hw.h
> +++ b/drivers/gpu/drm/panthor/panthor_hw.h
> @@ -19,6 +19,12 @@ struct panthor_hw_ops {
>
> /** @l2_power_on: L2 power on function pointer */
> int (*l2_power_on)(struct panthor_device *ptdev);
> +
> + /** @power_changed_on: Start listening to power change IRQs */
> + int (*power_changed_on)(struct panthor_device *ptdev);
> +
> + /** @power_changed_off: Stop listening to power change IRQs */
> + void (*power_changed_off)(struct panthor_device *ptdev);
> };
>
> /**
> @@ -32,6 +38,8 @@ struct panthor_hw {
> };
>
> int panthor_hw_init(struct panthor_device *ptdev);
> +int panthor_hw_power_status_register(void);
> +void panthor_hw_power_status_unregister(void);
>
> static inline int panthor_hw_soft_reset(struct panthor_device *ptdev)
> {
> diff --git a/drivers/gpu/drm/panthor/panthor_trace.h
> b/drivers/gpu/drm/panthor/panthor_trace.h
> new file mode 100644
> index 000000000000..2b59d7f156b6
> --- /dev/null
> +++ b/drivers/gpu/drm/panthor/panthor_trace.h
> @@ -0,0 +1,59 @@
> +/* 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>
> +
> +int panthor_hw_power_status_register(void);
> +void panthor_hw_power_status_unregister(void);
Hello, not sure if I'm missing something but, would doing
#include "panthor_hw.h"
address the need to redeclare panthor_hw_power_status_* in this file?
The change looks good otherwise.
Reviewed-by: Karunika Choo <[email protected]>
> +
> +/**
> + * gpu_power_status - called whenever parts of GPU hardware are turned on or
> off
> + * @dev: pointer to the &struct device, for printing the device name
> + * @shader_bitmap: bitmap where a high bit indicates the shader core at a
> given
> + * bit index is on, and a low bit indicates a shader core is
> + * either powered off or absent
> + * @tiler_bitmap: bitmap where a high bit indicates the tiler unit at a given
> + * bit index is on, and a low bit indicates a tiler unit is
> + * either powered off or absent
> + * @l2_bitmap: bitmap where a high bit indicates the L2 cache at a given bit
> + * index is on, and a low bit indicates the L2 cache is either
> + * powered off or absent
> + */
> +TRACE_EVENT_FN(gpu_power_status,
> + TP_PROTO(const struct device *dev, u64 shader_bitmap, u64 tiler_bitmap,
> + u64 l2_bitmap),
> + TP_ARGS(dev, shader_bitmap, tiler_bitmap, l2_bitmap),
> + TP_STRUCT__entry(
> + __string(dev_name, dev_name(dev))
> + __field(u64, shader_bitmap)
> + __field(u64, tiler_bitmap)
> + __field(u64, l2_bitmap)
> + ),
> + TP_fast_assign(
> + __assign_str(dev_name);
> + __entry->shader_bitmap = shader_bitmap;
> + __entry->tiler_bitmap = tiler_bitmap;
> + __entry->l2_bitmap = l2_bitmap;
> + ),
> + TP_printk("%s: shader_bitmap=0x%llx tiler_bitmap=0x%llx
> l2_bitmap=0x%llx",
> + __get_str(dev_name), __entry->shader_bitmap,
> __entry->tiler_bitmap,
> + __entry->l2_bitmap
> + ),
> + panthor_hw_power_status_register, panthor_hw_power_status_unregister
> +);
> +
> +#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>
>
