[PATCH v3 08/15] drm/panfrost: Use a threaded IRQ for job interrupts

[Steven Price]

On 25/06/2021 14:33, Boris Brezillon wrote:
> This should avoid switching to interrupt context when the GPU is under
> heavy use.
> 
> v3:
> * Don't take the job_lock in panfrost_job_handle_irq()
> 
> Signed-off-by: Boris Brezillon <boris.brezillon at collabora.com>

Reviewed-by: Steven Price <steven.price at arm.com>

> ---
>  drivers/gpu/drm/panfrost/panfrost_job.c | 53 ++++++++++++++++++-------
>  1 file changed, 38 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
> index be8f68f63974..e0c479e67304 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_job.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
> @@ -470,19 +470,12 @@ static const struct drm_sched_backend_ops panfrost_sched_ops = {
>  	.free_job = panfrost_job_free
>  };
>  
> -static irqreturn_t panfrost_job_irq_handler(int irq, void *data)
> +static void panfrost_job_handle_irq(struct panfrost_device *pfdev, u32 status)
>  {
> -	struct panfrost_device *pfdev = data;
> -	u32 status = job_read(pfdev, JOB_INT_STAT);
>  	int j;
>  
>  	dev_dbg(pfdev->dev, "jobslot irq status=%x\n", status);
>  
> -	if (!status)
> -		return IRQ_NONE;
> -
> -	pm_runtime_mark_last_busy(pfdev->dev);
> -
>  	for (j = 0; status; j++) {
>  		u32 mask = MK_JS_MASK(j);
>  
> @@ -519,7 +512,6 @@ static irqreturn_t panfrost_job_irq_handler(int irq, void *data)
>  		if (status & JOB_INT_MASK_DONE(j)) {
>  			struct panfrost_job *job;
>  
> -			spin_lock(&pfdev->js->job_lock);
>  			job = pfdev->jobs[j];
>  			/* Only NULL if job timeout occurred */
>  			if (job) {
> @@ -531,21 +523,49 @@ static irqreturn_t panfrost_job_irq_handler(int irq, void *data)
>  				dma_fence_signal_locked(job->done_fence);
>  				pm_runtime_put_autosuspend(pfdev->dev);
>  			}
> -			spin_unlock(&pfdev->js->job_lock);
>  		}
>  
>  		status &= ~mask;
>  	}
> +}
>  
> +static irqreturn_t panfrost_job_irq_handler_thread(int irq, void *data)
> +{
> +	struct panfrost_device *pfdev = data;
> +	u32 status = job_read(pfdev, JOB_INT_RAWSTAT);
> +
> +	while (status) {
> +		pm_runtime_mark_last_busy(pfdev->dev);
> +
> +		spin_lock(&pfdev->js->job_lock);
> +		panfrost_job_handle_irq(pfdev, status);
> +		spin_unlock(&pfdev->js->job_lock);
> +		status = job_read(pfdev, JOB_INT_RAWSTAT);
> +	}
> +
> +	job_write(pfdev, JOB_INT_MASK,
> +		  GENMASK(16 + NUM_JOB_SLOTS - 1, 16) |
> +		  GENMASK(NUM_JOB_SLOTS - 1, 0));
>  	return IRQ_HANDLED;
>  }
>  
> +static irqreturn_t panfrost_job_irq_handler(int irq, void *data)
> +{
> +	struct panfrost_device *pfdev = data;
> +	u32 status = job_read(pfdev, JOB_INT_STAT);
> +
> +	if (!status)
> +		return IRQ_NONE;
> +
> +	job_write(pfdev, JOB_INT_MASK, 0);
> +	return IRQ_WAKE_THREAD;
> +}
> +
>  static void panfrost_reset(struct work_struct *work)
>  {
>  	struct panfrost_device *pfdev = container_of(work,
>  						     struct panfrost_device,
>  						     reset.work);
> -	unsigned long flags;
>  	unsigned int i;
>  	bool cookie;
>  
> @@ -575,7 +595,7 @@ static void panfrost_reset(struct work_struct *work)
>  	/* All timers have been stopped, we can safely reset the pending state. */
>  	atomic_set(&pfdev->reset.pending, 0);
>  
> -	spin_lock_irqsave(&pfdev->js->job_lock, flags);
> +	spin_lock(&pfdev->js->job_lock);
>  	for (i = 0; i < NUM_JOB_SLOTS; i++) {
>  		if (pfdev->jobs[i]) {
>  			pm_runtime_put_noidle(pfdev->dev);
> @@ -583,7 +603,7 @@ static void panfrost_reset(struct work_struct *work)
>  			pfdev->jobs[i] = NULL;
>  		}
>  	}
> -	spin_unlock_irqrestore(&pfdev->js->job_lock, flags);
> +	spin_unlock(&pfdev->js->job_lock);
>  
>  	panfrost_device_reset(pfdev);
>  
> @@ -610,8 +630,11 @@ int panfrost_job_init(struct panfrost_device *pfdev)
>  	if (irq <= 0)
>  		return -ENODEV;
>  
> -	ret = devm_request_irq(pfdev->dev, irq, panfrost_job_irq_handler,
> -			       IRQF_SHARED, KBUILD_MODNAME "-job", pfdev);
> +	ret = devm_request_threaded_irq(pfdev->dev, irq,
> +					panfrost_job_irq_handler,
> +					panfrost_job_irq_handler_thread,
> +					IRQF_SHARED, KBUILD_MODNAME "-job",
> +					pfdev);
>  	if (ret) {
>  		dev_err(pfdev->dev, "failed to request job irq");
>  		return ret;
>