[PATCH v2 4/5] drm/panthor: Let IRQ handlers clear the interrupts themselves

[Liviu Dudau]

On Tue, Apr 01, 2025 at 08:23:47PM +0200, Boris Brezillon wrote:
> MMU handler needs to be in control of the job interrupt clears because
> clearing the interrupt also unblocks the writer/reader that triggered
> the fault, and we don't want it to be unblocked until we've had a chance
> to process the IRQ.
> 
> Since clearing the clearing is just one line, let's make it explicit
> instead of doing it in the generic code path.
> 
> Changes in v2:
> - Move the MMU_INT_CLEAR around
> 
> Signed-off-by: Boris Brezillon <boris.brezillon at collabora.com>

Reviewed-by: Liviu Dudau <liviu.dudau at arm.com>

Best regards,
Liviu

> ---
>  drivers/gpu/drm/panthor/panthor_device.h | 2 --
>  drivers/gpu/drm/panthor/panthor_fw.c     | 2 ++
>  drivers/gpu/drm/panthor/panthor_gpu.c    | 2 ++
>  drivers/gpu/drm/panthor/panthor_mmu.c    | 5 +++++
>  4 files changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
> index da6574021664..4c27b6d85f46 100644
> --- a/drivers/gpu/drm/panthor/panthor_device.h
> +++ b/drivers/gpu/drm/panthor/panthor_device.h
> @@ -383,8 +383,6 @@ static irqreturn_t panthor_ ## __name ## _irq_threaded_handler(int irq, void *da
>  		if (!status)									\
>  			break;									\
>  												\
> -		gpu_write(ptdev, __reg_prefix ## _INT_CLEAR, status);				\
> -												\
>  		__handler(ptdev, status);							\
>  		ret = IRQ_HANDLED;								\
>  	}											\
> diff --git a/drivers/gpu/drm/panthor/panthor_fw.c b/drivers/gpu/drm/panthor/panthor_fw.c
> index 0f52766a3120..446bb377b953 100644
> --- a/drivers/gpu/drm/panthor/panthor_fw.c
> +++ b/drivers/gpu/drm/panthor/panthor_fw.c
> @@ -1008,6 +1008,8 @@ static void panthor_fw_init_global_iface(struct panthor_device *ptdev)
>  
>  static void panthor_job_irq_handler(struct panthor_device *ptdev, u32 status)
>  {
> +	gpu_write(ptdev, JOB_INT_CLEAR, status);
> +
>  	if (!ptdev->fw->booted && (status & JOB_INT_GLOBAL_IF))
>  		ptdev->fw->booted = true;
>  
> diff --git a/drivers/gpu/drm/panthor/panthor_gpu.c b/drivers/gpu/drm/panthor/panthor_gpu.c
> index 671049020afa..32d678a0114e 100644
> --- a/drivers/gpu/drm/panthor/panthor_gpu.c
> +++ b/drivers/gpu/drm/panthor/panthor_gpu.c
> @@ -150,6 +150,8 @@ static void panthor_gpu_init_info(struct panthor_device *ptdev)
>  
>  static void panthor_gpu_irq_handler(struct panthor_device *ptdev, u32 status)
>  {
> +	gpu_write(ptdev, GPU_INT_CLEAR, status);
> +
>  	if (status & GPU_IRQ_FAULT) {
>  		u32 fault_status = gpu_read(ptdev, GPU_FAULT_STATUS);
>  		u64 address = ((u64)gpu_read(ptdev, GPU_FAULT_ADDR_HI) << 32) |
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> index 7cca97d298ea..4ac95a31907d 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -1710,6 +1710,11 @@ static void panthor_mmu_irq_handler(struct panthor_device *ptdev, u32 status)
>  			access_type, access_type_name(ptdev, fault_status),
>  			source_id);
>  
> +		/* We don't handle VM faults at the moment, so let's just clear the
> +		 * interrupt and let the writer/reader crash.
> +		 */
> +		gpu_write(ptdev, MMU_INT_CLEAR, mask);
> +
>  		/* Ignore MMU interrupts on this AS until it's been
>  		 * re-enabled.
>  		 */
> -- 
> 2.49.0
> 

-- 
====================
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| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
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