[PATCH v2 1/2] drm/panfrost: Use a threaded IRQ for job interrupts

[Steven Price]

On 21/06/2021 15:02, Boris Brezillon wrote:
> This should avoid uneccessary interrupt-context switches when the GPU
> is passed a lot of short jobs.

LGTM:

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

> 
> v2:
> * New patch
> 
> Signed-off-by: Boris Brezillon <boris.brezillon at collabora.com>
> ---
>  drivers/gpu/drm/panfrost/panfrost_job.c | 54 +++++++++++++++++--------
>  1 file changed, 38 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
> index cf6abe0fdf47..1b5c636794a1 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_job.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
> @@ -473,19 +473,12 @@ 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);
>  
> @@ -558,16 +551,43 @@ static irqreturn_t panfrost_job_irq_handler(int irq, void *data)
>  
>  		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, ~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;
>  
>  	for (i = 0; i < NUM_JOB_SLOTS; i++) {
> @@ -595,7 +615,7 @@ 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);
> @@ -603,7 +623,7 @@ 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);
>  
> @@ -628,8 +648,11 @@ 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;
> @@ -696,14 +719,13 @@ int panfrost_job_open(struct panfrost_file_priv *panfrost_priv)
>  void panfrost_job_close(struct panfrost_file_priv *panfrost_priv)
>  {
>  	struct panfrost_device *pfdev = panfrost_priv->pfdev;
> -	unsigned long flags;
>  	int i;
>  
>  	for (i = 0; i < NUM_JOB_SLOTS; i++)
>  		drm_sched_entity_destroy(&panfrost_priv->sched_entity[i]);
>  
>  	/* Kill in-flight jobs */
> -	spin_lock_irqsave(&pfdev->js->job_lock, flags);
> +	spin_lock(&pfdev->js->job_lock);
>  	for (i = 0; i < NUM_JOB_SLOTS; i++) {
>  		struct drm_sched_entity *entity = &panfrost_priv->sched_entity[i];
>  		struct panfrost_job *job = pfdev->jobs[i];
> @@ -713,7 +735,7 @@ void panfrost_job_close(struct panfrost_file_priv *panfrost_priv)
>  
>  		job_write(pfdev, JS_COMMAND(i), JS_COMMAND_HARD_STOP);
>  	}
> -	spin_unlock_irqrestore(&pfdev->js->job_lock, flags);
> +	spin_unlock(&pfdev->js->job_lock);
>  }
>  
>  int panfrost_job_is_idle(struct panfrost_device *pfdev)
>