Re: [PATCH v2 2/6] drm/i915: Only pin the fence for primary planes (and gen2/3)

["Guang (George) Bai" <guang.bai@intel.com>]

On Wed, 21 Feb 2018 20:48:07 +0200
Ville Syrjala <ville.syrjala@linux.intel.com> wrote:

> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Currently we pin a fence on every plane doing tiled scanout. The
> number of planes we have available is fast apporaching the number
> of fences so we really should stop wasting them. Only FBC needs
> the fence on gen4+, so let's use fences only for the primary planes
> on those platforms.
> 
> v2: drop the tiling check from plane_uses_fence() as the obj is
>     NULL during initial_plane_config() and we don't rally need the
>     check since i915_vma_pin_fence() does the check anyway
> 
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 14 +++++++++++++-
>  drivers/gpu/drm/i915/intel_drv.h     |  1 +
>  drivers/gpu/drm/i915/intel_fbdev.c   |  2 +-
>  3 files changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c
> b/drivers/gpu/drm/i915/intel_display.c index
> 66b269bc24b9..f2c1bb715e7b 100644 ---
> a/drivers/gpu/drm/i915/intel_display.c +++
> b/drivers/gpu/drm/i915/intel_display.c @@ -2067,9 +2067,18 @@ static
> unsigned int intel_surf_alignment(const struct drm_framebuffer *fb, }
>  }
>  
> +static bool intel_plane_uses_fence(const struct intel_plane_state
> *plane_state) +{
> +	struct intel_plane *plane =
> to_intel_plane(plane_state->base.plane);
> +	struct drm_i915_private *dev_priv = to_i915(plane->base.dev);
> +
> +	return INTEL_GEN(dev_priv) < 4 || plane->id == PLANE_PRIMARY;
> +}
> +
>  struct i915_vma *
>  intel_pin_and_fence_fb_obj(struct drm_framebuffer *fb,
>  			   unsigned int rotation,
> +			   bool uses_fence,
>  			   unsigned long *out_flags)
>  {
>  	struct drm_device *dev = fb->dev;
> @@ -2122,7 +2131,7 @@ intel_pin_and_fence_fb_obj(struct
> drm_framebuffer *fb, if (IS_ERR(vma))
>  		goto err;
>  
> -	if (i915_vma_is_map_and_fenceable(vma)) {
> +	if (uses_fence && i915_vma_is_map_and_fenceable(vma)) {
>  		int ret;
>  
>  		/* Install a fence for tiled scan-out. Pre-i965
> always needs a @@ -2836,6 +2845,7 @@
> intel_find_initial_plane_obj(struct intel_crtc *intel_crtc,
> intel_state->vma = intel_pin_and_fence_fb_obj(fb,
>  					   primary->state->rotation,
> +
> intel_plane_uses_fence(intel_state), &intel_state->flags);
>  	mutex_unlock(&dev->struct_mutex);
>  	if (IS_ERR(intel_state->vma)) {
> @@ -12744,6 +12754,7 @@ intel_prepare_plane_fb(struct drm_plane
> *plane, 
>  		vma = intel_pin_and_fence_fb_obj(fb,
>  						 new_state->rotation,
> +
> intel_plane_uses_fence(to_intel_plane_state(new_state)),
> &to_intel_plane_state(new_state)->flags); if (!IS_ERR(vma))
>  			to_intel_plane_state(new_state)->vma = vma;
> @@ -13162,6 +13173,7 @@ intel_legacy_cursor_update(struct drm_plane
> *plane, } else {
>  		vma = intel_pin_and_fence_fb_obj(fb,
>  						 new_plane_state->rotation,
> +						 false,
>  						 &to_intel_plane_state(new_plane_state)->flags);
>  		if (IS_ERR(vma)) {
>  			DRM_DEBUG_KMS("failed to pin object\n");
> diff --git a/drivers/gpu/drm/i915/intel_drv.h
> b/drivers/gpu/drm/i915/intel_drv.h index 50874f4035cf..e3f78fdae859
> 100644 --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1508,6 +1508,7 @@ void intel_release_load_detect_pipe(struct
> drm_connector *connector, struct i915_vma *
>  intel_pin_and_fence_fb_obj(struct drm_framebuffer *fb,
>  			   unsigned int rotation,
> +			   bool uses_fence,
>  			   unsigned long *out_flags);
>  void intel_unpin_fb_vma(struct i915_vma *vma, unsigned long flags);
>  struct drm_framebuffer *
> diff --git a/drivers/gpu/drm/i915/intel_fbdev.c
> b/drivers/gpu/drm/i915/intel_fbdev.c index 055f409f8b75..6f12adc06365
> 100644 --- a/drivers/gpu/drm/i915/intel_fbdev.c
> +++ b/drivers/gpu/drm/i915/intel_fbdev.c
> @@ -215,7 +215,7 @@ static int intelfb_create(struct drm_fb_helper
> *helper, */
>  	vma = intel_pin_and_fence_fb_obj(&ifbdev->fb->base,
>  					 DRM_MODE_ROTATE_0,
> -					 &flags);
> +					 false, &flags);
>  	if (IS_ERR(vma)) {
>  		ret = PTR_ERR(vma);
>  		goto out_unlock;

All these fence and fbc related changes will fix the gen9lp fence
starvation problems from virtualization use cases.
Thanks,
Guang
 
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