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

From: CK Hu
Date: Mon Dec 02 2019 - 04:52:05 EST

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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@xxxxxxxxxxxx>
> ---
> 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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