[Intel-gfx] [PATCH v6 1/3] drm/i915: Replaced Blitter ring based flips with MMIO flips

[Chris Wilson]

On Tue, May 20, 2014 at 04:19:46PM +0530, sourab.gupta at intel.com wrote:
> +int i915_gem_check_olr(struct intel_ring_buffer *ring, u32 seqno);

Be strict and add __must_check

> +static bool intel_use_mmio_flip(struct drm_device *dev)
> +{
> +	/* If module parameter is disabled, use CS flips.
> +	 * Otherwise, use MMIO flips starting from Gen5.
> +	 * This is not being used for older platforms because of
> +	 * non-availability of flip done interrupt.
> +	 */

What? Where is the dependence on flip-done?

> +	if (i915.use_mmio_flip == 0)
> +		return false;
> +
> +	if (INTEL_INFO(dev)->gen >= 5)
> +		return true;
> +	else
> +		return false;

You have not justified the change in default settings for existing hw.
Your argument is based on media power wells which does not support the
general change. It would seem that we may want to mix mmio / CS flips
depending on workload based on your vague statements.

I quite fancy a tristate here for force-CS flips, force-MMIO flips, at
driver discretion. Then enabling it on an architecture as a seperate
patch with justification - it is then easier to do each architecture on
a case-by-case basis and revert if need be.

> +static int intel_postpone_flip(struct drm_i915_gem_object *obj)
> +{
> +	int ret;

if (WARN_ON(crtc->mmio_flip_data.seqno)) return -EBUSY;

You need a tiling check here as you do not update dspcntr. Or fix
mmio_done.

> +	if (!obj->ring)
> +		return 0;
> +
> +	if (i915_seqno_passed(obj->ring->get_seqno(obj->ring, true),
> +				obj->last_write_seqno))
> +		return 0;
> +
> +	if (ret = i915_gem_check_olr(obj->ring, obj->last_write_seqno))
> +		return ret;

Please don't anger gcc.

> +
> +	if (WARN_ON(!obj->ring->irq_get(obj->ring)))
> +		return 0;
> +
> +	return 1;
> +}

> @@ -11377,6 +11497,9 @@ static void intel_init_display(struct drm_device *dev)
>  		break;
>  	}
>  
> +	if(intel_use_mmio_flip(dev))

Please don't anger checkpatch.

> +		dev_priv->display.queue_flip = intel_queue_mmio_flip;
> +
>  	intel_panel_init_backlight_funcs(dev);
>  }
>  
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 32a74e1..08d65a4 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -351,6 +351,11 @@ struct intel_pipe_wm {
>  	bool sprites_scaled;
>  };
>  
> +struct intel_mmio_flip {
> +	u32 seqno;
> +	u32 ring_id;
> +};
> +
>  struct intel_crtc {
>  	struct drm_crtc base;
>  	enum pipe pipe;
> @@ -403,6 +408,7 @@ struct intel_crtc {
>  	} wm;
>  
>  	wait_queue_head_t vbl_wait;
> +	struct intel_mmio_flip mmio_flip_data;

Does _data add anything meaningful here to the description of mmio_flip?
Just mmio_flip will suffice, as pending_mmio_flip is overkill but would
make a useful comment.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre