Re: [PATCH v7 7/8] drm/panthor: Add suspend, resume and reset handling

[Liviu Dudau <liviu.dudau@arm.com>]

Minor nit: subject line gives the wrong idea about the patch.

On Sun, Oct 11, 2026 at 06:36:54PM +0100, Lukas Zapolskas wrote:
> The sampler must disable and re-enable counter sampling around
> suspends, and must re-program the FW interface after a reset to
> avoid losing data. Additionally, if a request was pending before the
> reset and it was not acked, the reset will have cleared it, so we toggle
> the flag and re-request a sample.
> 
> Signed-off-by: Lukas Zapolskas <lukas.zapolskas@arm.com>
> ---
>  drivers/gpu/drm/panthor/panthor_device.c |  8 ++-
>  drivers/gpu/drm/panthor/panthor_perf.c   | 83 ++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/panthor/panthor_perf.h   |  6 +++
>  3 files changed, 96 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_device.c b/drivers/gpu/drm/panthor/panthor_device.c
> index 535383ef629f..c842480472ac 100644
> --- a/drivers/gpu/drm/panthor/panthor_device.c
> +++ b/drivers/gpu/drm/panthor/panthor_device.c
> @@ -138,6 +138,7 @@ static void panthor_device_reset_work(struct work_struct *work)
>  	if (!drm_dev_enter(&ptdev->base, &cookie))
>  		return;
>  
> +	panthor_perf_pre_reset(ptdev);
>  	panthor_sched_pre_reset(ptdev);
>  	panthor_fw_pre_reset(ptdev, true);
>  	panthor_mmu_pre_reset(ptdev);
> @@ -147,6 +148,8 @@ static void panthor_device_reset_work(struct work_struct *work)
>  	ret = panthor_fw_post_reset(ptdev);
>  	atomic_set(&ptdev->reset.pending, 0);
>  	panthor_sched_post_reset(ptdev, ret != 0);
> +	if (!ret)
> +		panthor_perf_post_reset(ptdev);
>  	drm_dev_exit(cookie);
>  
>  	if (ret) {
> @@ -539,8 +542,10 @@ int panthor_device_resume(struct device *dev)
>  			ret = panthor_device_resume_hw_components(ptdev);
>  		}
>  
> -		if (!ret)
> +		if (!ret) {
>  			panthor_sched_resume(ptdev);
> +			panthor_perf_resume(ptdev);
> +		}
>  
>  		drm_dev_exit(cookie);
>  
> @@ -604,6 +609,7 @@ int panthor_device_suspend(struct device *dev)
>  		/* We prepare everything as if we were resetting the GPU.
>  		 * The end of the reset will happen in the resume path though.
>  		 */
> +		panthor_perf_suspend(ptdev);
>  		panthor_sched_suspend(ptdev);
>  		panthor_fw_suspend(ptdev);
>  		panthor_mmu_suspend(ptdev);
> diff --git a/drivers/gpu/drm/panthor/panthor_perf.c b/drivers/gpu/drm/panthor/panthor_perf.c
> index c66ad658a95d..28b02003f9f9 100644
> --- a/drivers/gpu/drm/panthor/panthor_perf.c
> +++ b/drivers/gpu/drm/panthor/panthor_perf.c
> @@ -1798,6 +1798,57 @@ int panthor_perf_session_sample(struct panthor_file *pfile, u32 handle, u64 user
>  	return err;
>  }
>  
> +/**
> + * panthor_perf_suspend - Prepare the performance counter subsystem for system suspend.
> + * @ptdev: Panthor device.
> + *
> + * Indicate to the performance counters that the system is suspending.
> + *
> + * This function must not be used to handle MCU power state transitions: just before MCU goes
> + * from on to any inactive state, an automatic sample will be performed by the firmware, and
> + * the performance counter firmware state will be restored on warm boot.
> + *
> + */
> +void panthor_perf_suspend(struct panthor_device *ptdev)
> +{
> +	struct panthor_perf *perf = ptdev->perf;
> +	int ret;
> +
> +	if (!perf)
> +		return;
> +
> +	guard(mutex)(&perf->op_lock);
> +
> +	ret = perf_disable(perf);
> +
> +	if (ret)
> +		drm_warn(&ptdev->base, "Could not stop sampling before suspend, err = %d", ret);
> +}
> +
> +/**
> + * panthor_perf_resume - Resume the performance counter subsystem after system resumption.
> + * @ptdev: Panthor device.
> + *
> + * Indicate to the performance counters that the system has resumed. This must not be used
> + * to handle MCU state transitions, for the same reasons as detailed in the kerneldoc for
> + * @panthor_perf_suspend.
> + */
> +void panthor_perf_resume(struct panthor_device *ptdev)
> +{
> +	struct panthor_perf *perf = ptdev->perf;
> +	int ret;
> +
> +	if (!perf)
> +		return;
> +
> +	guard(mutex)(&perf->op_lock);
> +
> +	ret = perf_enable(perf);
> +
> +	if (ret)
> +		drm_warn(&ptdev->base, "Could not resume sampling, err = %d", ret);
> +}
> +
>  /**
>   * panthor_perf_unplug - Terminate the performance counter subsystem.
>   * @ptdev: Panthor device.
> @@ -1868,3 +1919,35 @@ void panthor_perf_pool_destroy(struct panthor_file *pfile)
>  
>  	pfile->sessions = NULL;
>  }
> +
> +void panthor_perf_pre_reset(struct panthor_device *ptdev)
> +{
> +	if (!ptdev->perf)
> +		return;
> +
> +	guard(mutex)(&ptdev->perf->op_lock);
> +
> +	perf_disable(ptdev->perf);
> +}
> +
> +void panthor_perf_post_reset(struct panthor_device *ptdev)
> +{
> +	bool rerequest = false;
> +
> +	if (!ptdev->perf)
> +		return;
> +
> +	guard(mutex)(&ptdev->perf->op_lock);
> +
> +	perf_enable(ptdev->perf);
> +
> +	scoped_guard(spinlock_irqsave, &ptdev->perf->pend_lock) {
> +		rerequest = ptdev->perf->fw_sample_requested;
> +
> +		if (rerequest)
> +			ptdev->perf->fw_sample_requested = false;
> +	}
> +
> +	if (rerequest)
> +		perf_fw_request_sample(ptdev->perf);
> +}
> diff --git a/drivers/gpu/drm/panthor/panthor_perf.h b/drivers/gpu/drm/panthor/panthor_perf.h
> index 0e1172dbae39..e4a323fe6f0d 100644
> --- a/drivers/gpu/drm/panthor/panthor_perf.h
> +++ b/drivers/gpu/drm/panthor/panthor_perf.h
> @@ -18,6 +18,8 @@ int panthor_perf_pool_create(struct panthor_file *pfile);
>  void panthor_perf_pool_destroy(struct panthor_file *pfile);
>  
>  int panthor_perf_init(struct panthor_device *ptdev);
> +void panthor_perf_suspend(struct panthor_device *ptdev);
> +void panthor_perf_resume(struct panthor_device *ptdev);
>  void panthor_perf_unplug(struct panthor_device *ptdev);
>  
>  int panthor_perf_session_create(struct drm_file *file,
> @@ -30,5 +32,9 @@ int panthor_perf_session_sample(struct panthor_file *pfile, unsigned int handle,
>  
>  void panthor_perf_report_irq(struct panthor_device *ptdev, u32 status);
>  
> +void panthor_perf_pre_reset(struct panthor_device *ptdev);
> +
> +void panthor_perf_post_reset(struct panthor_device *ptdev);
> +
>  #endif /* __PANTHOR_PERF_H__ */
>  
> 
> -- 
> 2.43.0
> 

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

Best regards,
Liviu

-- 
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