Re: [PATCH v1 4/6] drm/mediatek: update cursors by using async atomic update

[CK Hu <ck.hu@mediatek.com>]

Hi, Bibby:

On Thu, 2019-11-28 at 10:42 +0800, Bibby Hsieh wrote:
> Support to async updates of cursors by using the new atomic
> interface for that.
> 
> Signed-off-by: Bibby Hsieh <bibby.hsieh@mediatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_drm_crtc.c  | 35 +++++++++++++++++
>  drivers/gpu/drm/mediatek/mtk_drm_crtc.h  |  2 +
>  drivers/gpu/drm/mediatek/mtk_drm_drv.c   | 22 ++++++++++-
>  drivers/gpu/drm/mediatek/mtk_drm_drv.h   |  2 +
>  drivers/gpu/drm/mediatek/mtk_drm_plane.c | 50 ++++++++++++++++++++++++
>  drivers/gpu/drm/mediatek/mtk_drm_plane.h |  2 +
>  6 files changed, 112 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> index cb87a538b8ff..b26b7a98587b 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> @@ -422,6 +422,41 @@ int mtk_drm_crtc_plane_check(struct drm_crtc *crtc, struct drm_plane *plane,
>  	return 0;
>  }
>  
> +void mtk_drm_crtc_cursor_update(struct drm_crtc *crtc, struct drm_plane *plane,
> +				struct drm_plane_state *new_state)

I do not like to use 'cursor' for naming. The async function may be not
just used for cursor. The name 'async' is more general.

> +{
> +	struct mtk_drm_private *priv = crtc->dev->dev_private;
> +	struct mtk_drm_crtc *mtk_crtc = to_mtk_crtc(crtc);
> +	const struct drm_plane_helper_funcs *plane_helper_funcs =
> +			plane->helper_private;
> +	int i;
> +
> +	if (!mtk_crtc->enabled)
> +		return;
> +
> +	mutex_lock(&priv->hw_lock);

Please make sure what variable you want to protect, and make critical
section smaller.

> +	plane_helper_funcs->atomic_update(plane, new_state);
> +
> +	for (i = 0; i < mtk_crtc->layer_nr; i++) {
> +		struct drm_plane *plane = &mtk_crtc->planes[i];
> +		struct mtk_plane_state *plane_state;
> +
> +		plane_state = to_mtk_plane_state(plane->state);
> +		if (plane_state->pending.cursor_dirty) {
> +			plane_state->pending.config = true;
> +			plane_state->pending.cursor_update = false;
> +			plane_state->pending.cursor_dirty = false;
> +		}
> +	}
> +	mtk_crtc->pending_planes = true;
> +	if (priv->data->shadow_register) {
> +		mtk_disp_mutex_acquire(mtk_crtc->mutex);
> +		mtk_crtc_ddp_config(crtc);
> +		mtk_disp_mutex_release(mtk_crtc->mutex);
> +	}
> +	mutex_unlock(&priv->hw_lock);
> +}
> +
>  static void mtk_drm_crtc_atomic_enable(struct drm_crtc *crtc,
>  				       struct drm_crtc_state *old_state)
>  {
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.h b/drivers/gpu/drm/mediatek/mtk_drm_crtc.h
> index 6afe1c19557a..d57958f0b7b5 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.h
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.h
> @@ -21,5 +21,7 @@ int mtk_drm_crtc_create(struct drm_device *drm_dev,
>  			unsigned int path_len);
>  int mtk_drm_crtc_plane_check(struct drm_crtc *crtc, struct drm_plane *plane,
>  			     struct mtk_plane_state *state);
> +void mtk_drm_crtc_cursor_update(struct drm_crtc *crtc, struct drm_plane *plane,
> +				struct drm_plane_state *plane_state);
>  
>  #endif /* MTK_DRM_CRTC_H */
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> index 16e5771d182e..0f7fbb68295d 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> @@ -36,8 +36,27 @@
>  #define DRIVER_MAJOR 1
>  #define DRIVER_MINOR 0
>  
> +static void
> +mtk_drm_atomic_helper_commit_tail_rpm(struct drm_atomic_state *old_state)
> +{
> +	struct drm_device *dev = old_state->dev;
> +	struct mtk_drm_private *private = dev->dev_private;
> +
> +	drm_atomic_helper_wait_for_fences(dev, old_state, false);
> +	mutex_lock(&private->hw_lock);
> +	drm_atomic_helper_commit_modeset_disables(dev, old_state);
> +	drm_atomic_helper_commit_modeset_enables(dev, old_state);
> +	drm_atomic_helper_commit_planes(dev, old_state,
> +					DRM_PLANE_COMMIT_ACTIVE_ONLY);
> +	mutex_unlock(&private->hw_lock);

You implement mtk version just want to add mutex protect. But I think
you should not protect here because what you should protect is the
common variable touched by sync plane and async plane. In
mtk_drm_crtc_cursor_update(), you already know what is the variable you
need to protect, and these variable is touched in
mtk_drm_crtc_atomic_flush() or mtk_plane_atomic_update(), so I think you
should just protect inside these function and need not to implement this
function.

Regards,
CK

> +	drm_atomic_helper_fake_vblank(old_state);
> +	drm_atomic_helper_commit_hw_done(old_state);
> +	drm_atomic_helper_wait_for_vblanks(dev, old_state);
> +	drm_atomic_helper_cleanup_planes(dev, old_state);
> +}
> +
>  static const struct drm_mode_config_helper_funcs mtk_drm_mode_config_helpers = {
> -	.atomic_commit_tail = drm_atomic_helper_commit_tail_rpm,
> +	.atomic_commit_tail = mtk_drm_atomic_helper_commit_tail_rpm,
>  };
>  
>  static const struct drm_mode_config_funcs mtk_drm_mode_config_funcs = {
> @@ -262,6 +281,7 @@ static int mtk_drm_kms_init(struct drm_device *drm)
>  
>  	drm_kms_helper_poll_init(drm);
>  	drm_mode_config_reset(drm);
> +	mutex_init(&private->hw_lock);
>  
>  	return 0;
>  
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.h b/drivers/gpu/drm/mediatek/mtk_drm_drv.h
> index 9f4ce60174f6..c61adaa92626 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.h
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.h
> @@ -48,6 +48,8 @@ struct mtk_drm_private {
>  	const struct mtk_mmsys_driver_data *data;
>  	struct drm_atomic_state *suspend_state;
>  
> +	/* lock for display hw access */
> +	struct mutex hw_lock;
>  	bool dma_parms_allocated;
>  };
>  
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_plane.c b/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> index cd7c97eb7ee6..d7a8853d94a1 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> @@ -7,6 +7,7 @@
>  #include <drm/drm_atomic.h>
>  #include <drm/drm_atomic_helper.h>
>  #include <drm/drm_fourcc.h>
> +#include <drm/drm_atomic_uapi.h>
>  #include <drm/drm_plane_helper.h>
>  #include <drm/drm_gem_framebuffer_helper.h>
>  
> @@ -70,6 +71,50 @@ static void mtk_drm_plane_destroy_state(struct drm_plane *plane,
>  	kfree(to_mtk_plane_state(state));
>  }
>  
> +static int mtk_plane_atomic_async_check(struct drm_plane *plane,
> +					struct drm_plane_state *state)
> +{
> +	struct drm_crtc_state *crtc_state;
> +
> +	if (plane != state->crtc->cursor)
> +		return -EINVAL;
> +
> +	if (!plane->state)
> +		return -EINVAL;
> +
> +	if (!plane->state->fb)
> +		return -EINVAL;
> +
> +	if (state->state)
> +		crtc_state = drm_atomic_get_existing_crtc_state(state->state,
> +								state->crtc);
> +	else /* Special case for asynchronous cursor updates. */
> +		crtc_state = state->crtc->state;
> +
> +	return drm_atomic_helper_check_plane_state(plane->state, crtc_state,
> +						   DRM_PLANE_HELPER_NO_SCALING,
> +						   DRM_PLANE_HELPER_NO_SCALING,
> +						   true, true);
> +}
> +
> +static void mtk_plane_atomic_async_update(struct drm_plane *plane,
> +					  struct drm_plane_state *new_state)
> +{
> +	struct mtk_plane_state *state = to_mtk_plane_state(plane->state);
> +
> +	plane->state->crtc_x = new_state->crtc_x;
> +	plane->state->crtc_y = new_state->crtc_y;
> +	plane->state->crtc_h = new_state->crtc_h;
> +	plane->state->crtc_w = new_state->crtc_w;
> +	plane->state->src_x = new_state->src_x;
> +	plane->state->src_y = new_state->src_y;
> +	plane->state->src_h = new_state->src_h;
> +	plane->state->src_w = new_state->src_w;
> +	state->pending.cursor_update = true;
> +
> +	mtk_drm_crtc_cursor_update(new_state->crtc, plane, new_state);
> +}
> +
>  static const struct drm_plane_funcs mtk_plane_funcs = {
>  	.update_plane = drm_atomic_helper_update_plane,
>  	.disable_plane = drm_atomic_helper_disable_plane,
> @@ -141,6 +186,9 @@ static void mtk_plane_atomic_update(struct drm_plane *plane,
>  	state->pending.rotation = plane->state->rotation;
>  	wmb(); /* Make sure the above parameters are set before update */
>  	state->pending.dirty = true;
> +
> +	if (state->pending.cursor_update)
> +		state->pending.cursor_dirty = true;
>  }
>  
>  static void mtk_plane_atomic_disable(struct drm_plane *plane,
> @@ -158,6 +206,8 @@ static const struct drm_plane_helper_funcs mtk_plane_helper_funcs = {
>  	.atomic_check = mtk_plane_atomic_check,
>  	.atomic_update = mtk_plane_atomic_update,
>  	.atomic_disable = mtk_plane_atomic_disable,
> +	.atomic_async_update = mtk_plane_atomic_async_update,
> +	.atomic_async_check = mtk_plane_atomic_async_check,
>  };
>  
>  int mtk_plane_init(struct drm_device *dev, struct drm_plane *plane,
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_plane.h b/drivers/gpu/drm/mediatek/mtk_drm_plane.h
> index 760885e35b27..113a10344805 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_plane.h
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_plane.h
> @@ -22,6 +22,8 @@ struct mtk_plane_pending_state {
>  	unsigned int			height;
>  	unsigned int			rotation;
>  	bool				dirty;
> +	bool				cursor_dirty;
> +	bool				cursor_update;
>  };
>  
>  struct mtk_plane_state {


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