On Fri, 16 Jan 2026 13:57:32 +0100 Nicolas Frattaroli <[email protected]> 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 | 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" > + > /** > * struct panthor_gpu - GPU block management data. > */ > @@ -48,6 +51,9 @@ 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 +86,12 @@ 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); > @@ -157,6 +169,22 @@ int panthor_gpu_init(struct panthor_device *ptdev) > return 0; > } > > +int panthor_gpu_power_changed_on(struct panthor_device *ptdev) > +{ > + guard(pm_runtime_active)(ptdev->base.dev); > + > + panthor_gpu_irq_enable_events(&ptdev->gpu->irq, > GPU_POWER_INTERRUPTS_MASK); > + > + return 0; > +} > + > +void panthor_gpu_power_changed_off(struct panthor_device *ptdev) > +{ > + guard(pm_runtime_active)(ptdev->base.dev); > + > + panthor_gpu_irq_disable_events(&ptdev->gpu->irq, > GPU_POWER_INTERRUPTS_MASK); > +} > + > /** > * panthor_gpu_block_power_off() - Power-off a specific block of the GPU > * @ptdev: Device. > 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 80c521784cd3..d135aa6724fa 100644 > --- a/drivers/gpu/drm/panthor/panthor_hw.c > +++ b/drivers/gpu/drm/panthor/panthor_hw.c > @@ -2,6 +2,8 @@ > /* Copyright 2025 ARM Limited. All rights reserved. */ > > #include <linux/nvmem-consumer.h> > +#include <linux/platform_device.h> > + > #include <drm/drm_print.h> > > #include "panthor_device.h" > @@ -30,6 +32,8 @@ 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, > }, > }; > > @@ -54,6 +58,64 @@ 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; > +} nit: since you've already exposed the power transition monitoring through two different callbacks, could we also do the same here, with two panthor_hw_power_tracing_{on,off}() functions which ignore the data (not a huge fan of this bool->pointer cast). static int panthor_hw_power_tracing_on(struct device *dev, void *data) { struct panthor_device *ptdev = dev_get_drvdata(dev); if (!ptdev) return -ENODEV; if (ptdev->hw && ptdev->hw->ops.power_changed_on) return ptdev->hw->ops.power_changed_on(ptdev); return 0; } static int panthor_hw_power_tracing_off(struct device *dev, void *data) { struct panthor_device *ptdev = dev_get_drvdata(dev); if (!ptdev) return -ENODEV; if (ptdev->hw && ptdev->hw->ops.power_changed_off) return ptdev->hw->ops.power_changed_off(ptdev); return 0; } Feel free to ignore, this patch is Reviewed-by: Boris Brezillon <[email protected]> regardless. > + > +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..5bd420894745 > --- /dev/null > +++ b/drivers/gpu/drm/panthor/panthor_trace.h > @@ -0,0 +1,58 @@ > +/* 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> > + > +#include "panthor_hw.h" > + > +/** > + * 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> >
