Re: [RFC 13/15] drm/i915: Introduce intel_schedule_vblank_job()

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, May 20, 2015 at 07:12:25PM -0700, Matt Roper wrote:
> Various places in the driver need the ability to schedule actions to run
> on a future vblank (updating watermarks, unpinning buffers, etc.).  The
> long term goal is to add such a mechanism in the DRM core that can be
> shared by all drivers.  Paulo Zanoni has already written some
> preliminary patches to support this, but his work will probably take
> some time to polish and get merged since it needs to untangle the DRM
> core's vblank infrastructure.  This patch is partially based on Paulo's
> work, but takes a simpler approach and just adds an i915-specific
> mechanism that can be used in the interim since we have an immediate
> need for watermark updates.
> 
> Inspired-by: Paulo Zanoni <przanoni@gmail.com>
> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>

I like what I had better. No needless kmallocs (this IMO is a must
requirement for any solution), no needless workqueues, uses the hw
vblank counter and absolute values so isn't racy.

> ---
>  drivers/gpu/drm/i915/i915_irq.c      | 117 +++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_display.c |   8 +++
>  drivers/gpu/drm/i915/intel_drv.h     |  27 ++++++++
>  3 files changed, 152 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index 557af88..fd5a795 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -1649,8 +1649,37 @@ static void gen6_rps_irq_handler(struct drm_i915_private *dev_priv, u32 pm_iir)
>  	}
>  }
>  
> +static void process_vblank_jobs(struct drm_device *dev, enum pipe pipe)
> +{
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +	struct drm_crtc *crtc = dev_priv->pipe_to_crtc_mapping[pipe];
> +	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
> +	struct i915_vblank_job *job, *tmp;
> +	u32 seq;
> +
> +	seq = drm_vblank_count(dev, pipe);
> +	list_for_each_entry_safe(job, tmp, &intel_crtc->vblank_jobs, link) {
> +		if (seq - job->seq > (1<<23))
> +			continue;
> +
> +		list_del(&job->link);
> +		drm_vblank_put(dev, pipe);
> +
> +		if (job->wq) {
> +			job->fired_seq = seq;
> +			queue_work(job->wq, &job->work);
> +		} else {
> +			job->callback(intel_crtc, job->callback_data,
> +				      false, seq);
> +			kfree(job);
> +		}
> +	}
> +}
> +
>  static bool intel_pipe_handle_vblank(struct drm_device *dev, enum pipe pipe)
>  {
> +	process_vblank_jobs(dev, pipe);
> +
>  	if (!drm_handle_vblank(dev, pipe))
>  		return false;
>  
> @@ -4511,3 +4540,91 @@ void intel_runtime_pm_enable_interrupts(struct drm_i915_private *dev_priv)
>  	dev_priv->dev->driver->irq_preinstall(dev_priv->dev);
>  	dev_priv->dev->driver->irq_postinstall(dev_priv->dev);
>  }
> +
> +static void vblank_job_handler(struct work_struct *work)
> +{
> +	struct i915_vblank_job *job =
> +		container_of(work, struct i915_vblank_job, work);
> +
> +	job->callback(job->crtc, job->callback_data,
> +		      job->seq != job->fired_seq, job->fired_seq);
> +	kfree(job);
> +}
> +
> +/**
> + * intel_schedule_vblank_job - schedule work to happen on specified vblank
> + * @crtc: CRTC whose vblank should trigger the work
> + * @callback: Code to run on vblank
> + * @callback_data: Data to pass to callback function
> + * @wq: Workqueue to run job on (or NULL to run from interrupt context)
> + * @seq: vblank count relative to current to schedule for
> + *
> + * Schedule code that should be run after the specified vblank fires.  The code
> + * can either run directly in the interrupt context or on a specified
> + * workqueue.
> + */
> +int intel_schedule_vblank_job(struct intel_crtc *crtc,
> +			      i915_vblank_callback_t callback,
> +			      void *callback_data,
> +			      struct workqueue_struct *wq,
> +			      u32 seq)
> +{
> +	struct drm_device *dev = crtc->base.dev;
> +	struct i915_vblank_job *job;
> +	unsigned long irqflags;
> +	int ret;
> +
> +	job = kzalloc(sizeof(*job), GFP_ATOMIC);
> +	if (!job)
> +		return -ENOMEM;
> +
> +	job->wq = wq;
> +	job->crtc = crtc;
> +	job->callback = callback;
> +	job->callback_data = callback_data;
> +	if (job->wq)
> +		INIT_WORK(&job->work, vblank_job_handler);
> +
> +	ret = drm_crtc_vblank_get(&crtc->base);
> +	if (ret) {
> +		DRM_DEBUG_KMS("Failed to enable interrupts, ret=%d\n", ret);
> +		kfree(job);
> +		return -EINVAL;
> +	}
> +
> +	spin_lock_irqsave(&dev->event_lock, irqflags);
> +	job->seq = seq + drm_vblank_count(dev, crtc->pipe);
> +	list_add_tail(&job->link, &crtc->vblank_jobs);
> +	spin_unlock_irqrestore(&dev->event_lock, irqflags);
> +
> +	return 0;
> +}
> +
> +/**
> + * intel_trigger_all_vblank_jobs - immediately trigger vblank jobs for a crtc
> + * @crtc: CRTC to trigger all outstanding jobs for
> + *
> + * Immediately triggers all of the jobs awaiting future vblanks on a CRTC.
> + * This will be called when a CRTC is disabled (because there may never be
> + * another vblank event).  The job callbacks will receive 'true' for the
> + * early parameter, as well as the current vblank count.
> + */
> +void trigger_all_vblank_jobs(struct intel_crtc *crtc)
> +{
> +	struct i915_vblank_job *job, *tmp;
> +	u32 seq;
> +
> +	seq = drm_vblank_count(crtc->base.dev, crtc->pipe);
> +	list_for_each_entry_safe(job, tmp, &crtc->vblank_jobs, link) {
> +		list_del(&job->link);
> +		drm_vblank_put(crtc->base.dev, crtc->pipe);
> +
> +		if (job->wq) {
> +			job->fired_seq = seq;
> +			queue_work(job->wq, &job->work);
> +		} else {
> +			job->callback(crtc, job->callback_data, true, seq);
> +			kfree(job);
> +		}
> +	}
> +}
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 76affba..9b56d07 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -5099,6 +5099,8 @@ static void ironlake_crtc_disable(struct drm_crtc *crtc)
>  	if (!intel_crtc->active)
>  		return;
>  
> +	trigger_all_vblank_jobs(intel_crtc);
> +
>  	for_each_encoder_on_crtc(dev, crtc, encoder)
>  		encoder->disable(encoder);
>  
> @@ -5161,6 +5163,8 @@ static void haswell_crtc_disable(struct drm_crtc *crtc)
>  	if (!intel_crtc->active)
>  		return;
>  
> +	trigger_all_vblank_jobs(intel_crtc);
> +
>  	for_each_encoder_on_crtc(dev, crtc, encoder) {
>  		intel_opregion_notify_encoder(encoder, false);
>  		encoder->disable(encoder);
> @@ -6004,6 +6008,8 @@ static void i9xx_crtc_disable(struct drm_crtc *crtc)
>  	if (!intel_crtc->active)
>  		return;
>  
> +	trigger_all_vblank_jobs(intel_crtc);
> +
>  	/*
>  	 * On gen2 planes are double buffered but the pipe isn't, so we must
>  	 * wait for planes to fully turn off before disabling the pipe.
> @@ -13649,6 +13655,8 @@ static void intel_crtc_init(struct drm_device *dev, int pipe)
>  
>  	drm_crtc_helper_add(&intel_crtc->base, &intel_helper_funcs);
>  
> +	INIT_LIST_HEAD(&intel_crtc->vblank_jobs);
> +
>  	WARN_ON(drm_crtc_index(&intel_crtc->base) != intel_crtc->pipe);
>  	return;
>  
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 627741a..630e7c1 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -504,6 +504,24 @@ struct intel_crtc_atomic_commit {
>  	unsigned update_sprite_watermarks;
>  };
>  
> +typedef void (*i915_vblank_callback_t)(struct intel_crtc *crtc,
> +				       void *data,
> +				       bool early,
> +				       u32 fired_seq);
> +
> +/* Task to run (or schedule on a workqueue) on a specific vblank */
> +struct i915_vblank_job {
> +	u32 seq;
> +	u32 fired_seq;                     /* early if crtc gets disabled */
> +	struct intel_crtc *crtc;
> +	struct workqueue_struct *wq;       /* NULL = run from interrupt */
> +	i915_vblank_callback_t callback;
> +	void *callback_data;
> +
> +	struct list_head link;
> +	struct work_struct work;
> +};
> +
>  struct intel_crtc {
>  	struct drm_crtc base;
>  	enum pipe pipe;
> @@ -550,6 +568,9 @@ struct intel_crtc {
>  
>  	/* scalers available on this crtc */
>  	int num_scalers;
> +
> +	/* Jobs to run/schedule on vblank */
> +	struct list_head vblank_jobs;
>  };
>  
>  struct intel_plane_wm_parameters {
> @@ -913,6 +934,12 @@ static inline bool intel_irqs_enabled(struct drm_i915_private *dev_priv)
>  int intel_get_crtc_scanline(struct intel_crtc *crtc);
>  void gen8_irq_power_well_post_enable(struct drm_i915_private *dev_priv,
>  				     unsigned int pipe_mask);
> +int intel_schedule_vblank_job(struct intel_crtc *crtc,
> +			      i915_vblank_callback_t callback,
> +			      void *callback_data,
> +			      struct workqueue_struct *wq,
> +			      u32 seq);
> +void trigger_all_vblank_jobs(struct intel_crtc *crtc);
>  
>  /* intel_crt.c */
>  void intel_crt_init(struct drm_device *dev);
> -- 
> 1.8.5.1
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Ville Syrjälä
Intel OTC
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/intel-gfx