Re: [PATCH] drm/i915: Track pinned vma in intel_plane_state

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Op 04-01-17 om 16:47 schreef Ville Syrjälä:
> On Wed, Jan 04, 2017 at 03:14:45PM +0000, Chris Wilson wrote:
>> On Wed, Jan 04, 2017 at 05:06:46PM +0200, Ville Syrjälä wrote:
>>> On Wed, Jan 04, 2017 at 02:31:26PM +0100, Maarten Lankhorst wrote:
>>>> From: Chris Wilson <chris@chris-wilson.co.uk>
>>>>
>>>> With atomic plane states we are able to track an allocation right from
>>>> preparation, during use and through to the final free after being
>>>> swapped out for a new plane. We can couple the VMA we pin for the
>>>> framebuffer (and its rotation) to this lifetime and avoid all the clumsy
>>>> lookups in between.
>>>>
>>>> v2: Remove residual vma on plane cleanup (Chris)
>>>> v3: Add a description for the vma destruction in
>>>>     intel_plane_destroy_state (Maarten)
>>>>
>>>> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
>>>> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>>>> ---
>>>>  drivers/gpu/drm/i915/i915_drv.h           |  16 +---
>>>>  drivers/gpu/drm/i915/intel_atomic_plane.c |  20 +++++
>>>>  drivers/gpu/drm/i915/intel_display.c      | 129 +++++++++++-------------------
>>>>  drivers/gpu/drm/i915/intel_drv.h          |   9 ++-
>>>>  drivers/gpu/drm/i915/intel_fbc.c          |  52 +++++-------
>>>>  drivers/gpu/drm/i915/intel_fbdev.c        |   4 +-
>>>>  drivers/gpu/drm/i915/intel_sprite.c       |   8 +-
>>>>  7 files changed, 103 insertions(+), 135 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>>>> index 22d3f610212c..5369f5f9ce3a 100644
>>>> --- a/drivers/gpu/drm/i915/i915_drv.h
>>>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>>>> @@ -1079,6 +1079,8 @@ struct intel_fbc {
>>>>  	struct work_struct underrun_work;
>>>>  
>>>>  	struct intel_fbc_state_cache {
>>>> +		struct i915_vma *vma;
>>>> +
>>>>  		struct {
>>>>  			unsigned int mode_flags;
>>>>  			uint32_t hsw_bdw_pixel_rate;
>>>> @@ -1092,15 +1094,14 @@ struct intel_fbc {
>>>>  		} plane;
>>>>  
>>>>  		struct {
>>>> -			u64 ilk_ggtt_offset;
>>>>  			const struct drm_format_info *format;
>>>>  			unsigned int stride;
>>>> -			int fence_reg;
>>>> -			unsigned int tiling_mode;
>>>>  		} fb;
>>>>  	} state_cache;
>>>>  
>>>>  	struct intel_fbc_reg_params {
>>>> +		struct i915_vma *vma;
>>>> +
>>>>  		struct {
>>>>  			enum pipe pipe;
>>>>  			enum plane plane;
>>>> @@ -1108,10 +1109,8 @@ struct intel_fbc {
>>>>  		} crtc;
>>>>  
>>>>  		struct {
>>>> -			u64 ggtt_offset;
>>>>  			const struct drm_format_info *format;
>>>>  			unsigned int stride;
>>>> -			int fence_reg;
>>>>  		} fb;
>>>>  
>>>>  		int cfb_size;
>>>> @@ -3406,13 +3405,6 @@ i915_gem_object_to_ggtt(struct drm_i915_gem_object *obj,
>>>>  	return i915_gem_obj_to_vma(obj, &to_i915(obj->base.dev)->ggtt.base, view);
>>>>  }
>>>>  
>>>> -static inline unsigned long
>>>> -i915_gem_object_ggtt_offset(struct drm_i915_gem_object *o,
>>>> -			    const struct i915_ggtt_view *view)
>>>> -{
>>>> -	return i915_ggtt_offset(i915_gem_object_to_ggtt(o, view));
>>>> -}
>>>> -
>>>>  /* i915_gem_fence_reg.c */
>>>>  int __must_check i915_vma_get_fence(struct i915_vma *vma);
>>>>  int __must_check i915_vma_put_fence(struct i915_vma *vma);
>>>> diff --git a/drivers/gpu/drm/i915/intel_atomic_plane.c b/drivers/gpu/drm/i915/intel_atomic_plane.c
>>>> index 4612ffd555a7..41fd94e62d3c 100644
>>>> --- a/drivers/gpu/drm/i915/intel_atomic_plane.c
>>>> +++ b/drivers/gpu/drm/i915/intel_atomic_plane.c
>>>> @@ -85,6 +85,8 @@ intel_plane_duplicate_state(struct drm_plane *plane)
>>>>  
>>>>  	__drm_atomic_helper_plane_duplicate_state(plane, state);
>>>>  
>>>> +	intel_state->vma = NULL;
>>> Shouldn't we be doing vma_get() instead?
>> I went with NULL (dropping the copy) for simplicity. Before the plane
>> can be used it must be prepared, so vma will always be set before
>> commiting, and using NULL avoided having the reference counting dance.
>> It also allowed detection of when we didn't prepare the plane as
>> required.
> Hmm. Does that risk some kind of failure at prepare_fb time if the vma
> got nuked in the meantime? I guess that might ahve to involve
> suspend/resume or some other case where we duplicate the state and
> don't hang on to the old state.

I think the way this is done is sane, and a nice safeguard against forgetting to call prepare.
The old mapping is still around when prepare_plane_fb is called, and we keep the vma during suspend/resume
since we never unset the plane fb. We only set crtc_state->active = false (dpms off).

~Maarten

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