On Mon, Feb 08, 2021 at 02:50:43PM +0100, Thomas Zimmermann wrote:
> Export the helpers for shadow-buffered planes. These will be used by
> several drivers.
>
> Signed-off-by: Thomas Zimmermann <tzimmerm...@suse.de>
> ---
> drivers/gpu/drm/drm_gem_atomic_helper.c | 148 +++++++++++++++++++++++-
> include/drm/drm_gem_atomic_helper.h | 32 +++++
> 2 files changed, 174 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gem_atomic_helper.c
> b/drivers/gpu/drm/drm_gem_atomic_helper.c
> index e27762cef360..79b4d3f0495a 100644
> --- a/drivers/gpu/drm/drm_gem_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_gem_atomic_helper.c
> @@ -14,13 +14,101 @@
> * functions for drivers that use GEM objects. Currently, it provides
> * plane state and framebuffer BO mappings for planes with shadow
> * buffers.
> + *
> + * A driver using a shadow buffer copies the content of the shadow buffers
> + * into the HW's framebuffer memory during an atomic update. This requires
> + * a mapping of the shadow buffer into kernel address space. The mappings
> + * cannot be established by commit-tail functions, such as atomic_update,
> + * as this would violate locking rules vmap.
"... locking rules around dma_buf_vmap()"?
> + *
> + * The helpers for shadow-buffered planes establish and release mappings,
> + * and provide struct drm_shadow_plane_state, which stores the plane's
> mapping
> + * for commit-tail functons.
> + *
> + * Shadow-buffered planes can easily be enabled by using the provided macros
> + * DRM_GEM_PLANE_SHADOW_FUNCS and DRM_GEM_SHADOE_PLANE_HELPER_FUNCS.
I think for hyperlinks/highlights we need %CONSTANT? Maybe check what works.
> + * These macros set up the plane and plane-helper callbacks to point to the
> + * shadow-buffer helpers.
> + *
> + * .. code-block:: c
> + *
> + * #include <drm/drm/gem_atomic_helper.h>
> + *
> + * struct drm_plane_funcs driver_plane_funcs = {
> + * ...,
> + * DRM_GEM_SHADOW_PLANE_FUNCS,
> + * };
> + *
> + * struct drm_plane_helper_funcs driver_plane_helper_funcs = {
> + * ...,
> + * DRM_GEM_SHADOW_PLANE_HELPER_FUNCS,
> + * };
> + *
> + * In the driver's atomic-update function, shadow-buffer mappings are
> available
> + * from the plane state. Use to_drm_shadow_plane_state() to upcast from
> + * struct drm_plane_state.
> + *
> + * .. code-block:: c
> + *
> + * void driver_plane_atomic_update(struct drm_plane *plane,
> + * struct drm_plane_state *old_plane_state)
> + * {
> + * struct drm_plane_state *plane_state = plane->state;
> + * struct drm_shadow_plane_state *shadow_plane_state =
> + * to_drm_shadow_plane_state(plane_state);
> + *
> + * // access shadow buffer via shadow_plane_state->map
> + * }
> + *
> + * A mapping address for each of the framebuffer's buffer object is stored in
> + * struct drm_shadow_plane_state.map. The mappings are valid while the state
> + * is being used.
> + *
> + * Drivers that use struct drm_simple_display_pipe can use
> + * DRM_GEM_SIMPLE_DISPLAY_PIPE_SHADOW_PLANE_FUNCS to initialize the rsp
> + * callbacks. Access to shadow-buffer mappings is similar to regular
> + * atomic_update.
> + *
> + * .. code-block:: c
> + *
> + * struct drm_simple_display_pipe_funcs driver_pipe_funcs = {
> + * ...,
> + * DRM_GEM_SIMPLE_DISPLAY_PIPE_SHADOW_PLANE_FUNCS,
> + * };
> + *
> + * void driver_pipe_enable(struct drm_simple_display_pipe *pipe,
> + * struct drm_crtc_state *crtc_state,
> + * struct drm_plane_state *plane_state)
> + * {
> + * struct drm_shadow_plane_state *shadow_plane_state =
> + * to_drm_shadow_plane_state(plane_state);
> + *
> + * // access shadow buffer via shadow_plane_state->map
> + * }
> */
>
> /*
> * Shadow-buffered Planes
> */
>
> -static struct drm_plane_state *
> +/**
> + * drm_gem_duplicate_shadow_plane_state - duplicates shadow-buffered plane
> state
> + * @plane: the plane
> + *
> + * This function implements struct drm_plane_funcs.atomic_duplicate_state for
Does this hyperlink automatically? I didn't know it works since for
members I just always use &struct.member myself.
> + * shadow-buffered planes. It assumes the existing state to be of type
> + * struct drm_shadow_plane_state and it allocates the new state to be of this
> + * type.
> + *
> + * The function does not duplicate existing mappings of the shadow buffers.
> + * Mappings are maintained during the atomic commit by the plane's prepare_fb
> + * and cleanup_fb helpers. See drm_gem_prepare_shadow_fb() and
> drm_gem_cleanup_shadow_fb()
> + * for corresponding helpers.
> + *
> + * Returns:
> + * A pointer to a new plane state on success, or NULL otherwise.
> + */
> +struct drm_plane_state *
> drm_gem_duplicate_shadow_plane_state(struct drm_plane *plane)
> {
> struct drm_plane_state *plane_state = plane->state;
> @@ -36,9 +124,19 @@ drm_gem_duplicate_shadow_plane_state(struct drm_plane
> *plane)
>
> return &new_shadow_plane_state->base;
> }
> +EXPORT_SYMBOL(drm_gem_duplicate_shadow_plane_state);
>
> -static void drm_gem_destroy_shadow_plane_state(struct drm_plane *plane,
> - struct drm_plane_state
> *plane_state)
> +/**
> + * drm_gem_destroy_shadow_plane_state - deletes shadow-buffered plane state
> + * @plane: the plane
> + * @plane_state: the plane state of type struct drm_shadow_plane_state
> + *
> + * This function implements struct drm_plane_funcs.atomic_destroy_state
> + * for shadow-buffered planes. It expects that mappings of shadow buffers
> + * have been released already.
> + */
> +void drm_gem_destroy_shadow_plane_state(struct drm_plane *plane,
> + struct drm_plane_state *plane_state)
> {
> struct drm_shadow_plane_state *shadow_plane_state =
> to_drm_shadow_plane_state(plane_state);
> @@ -46,8 +144,18 @@ static void drm_gem_destroy_shadow_plane_state(struct
> drm_plane *plane,
> __drm_atomic_helper_plane_destroy_state(&shadow_plane_state->base);
> kfree(shadow_plane_state);
> }
> +EXPORT_SYMBOL(drm_gem_destroy_shadow_plane_state);
>
> -static void drm_gem_reset_shadow_plane(struct drm_plane *plane)
> +/**
> + * drm_gem_reset_shadow_plane - resets a shadow-buffered plane
> + * @plane: the plane
> + *
> + * This function implements struct drm_plane_funcs.reset_plane for
> + * shadow-buffered planes. It assumes the current plane state to be
> + * of type struct drm_shadow_plane and it allocates the new state of
> + * this type.
> + */
> +void drm_gem_reset_shadow_plane(struct drm_plane *plane)
> {
> struct drm_shadow_plane_state *shadow_plane_state;
>
> @@ -61,8 +169,24 @@ static void drm_gem_reset_shadow_plane(struct drm_plane
> *plane)
> return;
> __drm_atomic_helper_plane_reset(plane, &shadow_plane_state->base);
> }
> +EXPORT_SYMBOL(drm_gem_reset_shadow_plane);
>
> -static int drm_gem_prepare_shadow_fb(struct drm_plane *plane, struct
> drm_plane_state *plane_state)
> +/**
> + * drm_gem_prepare_shadow_fb - prepares shadow framebuffers
> + * @plane: the plane
> + * @plane_state: the plane state of type struct drm_shadow_plane_state
> + *
> + * This function implements struct drm_plane_helper_funcs.prepare_fb. It
> + * maps all buffer objects of the plane's framebuffer into kernel address
> + * space and stores them in struct drm_shadow_plane_state.map. The
> + * framebuffer will be synchronized as part of the atomic commit.
> + *
> + * See drm_gem_cleanup_shadow_fb() for cleanup.
> + *
> + * Returns:
> + * 0 on success, or a negative errno code otherwise.
> + */
> +int drm_gem_prepare_shadow_fb(struct drm_plane *plane, struct
> drm_plane_state *plane_state)
> {
> struct drm_shadow_plane_state *shadow_plane_state =
> to_drm_shadow_plane_state(plane_state);
> struct drm_framebuffer *fb = plane_state->fb;
> @@ -100,8 +224,19 @@ static int drm_gem_prepare_shadow_fb(struct drm_plane
> *plane, struct drm_plane_s
> }
> return ret;
> }
> +EXPORT_SYMBOL(drm_gem_prepare_shadow_fb);
>
> -static void drm_gem_cleanup_shadow_fb(struct drm_plane *plane, struct
> drm_plane_state *plane_state)
> +/**
> + * drm_gem_cleanup_shadow_fb - releases shadow framebuffers
> + * @plane: the plane
> + * @plane_state: the plane state of type struct drm_shadow_plane_state
> + *
> + * This function implements struct drm_plane_helper_funcs.cleanup_fb.
> + * This function unmaps all buffer objects of the plane's framebuffer.
> + *
> + * See drm_gem_prepare_shadow_fb() for more inforamtion.
> + */
> +void drm_gem_cleanup_shadow_fb(struct drm_plane *plane, struct
> drm_plane_state *plane_state)
> {
> struct drm_shadow_plane_state *shadow_plane_state =
> to_drm_shadow_plane_state(plane_state);
> struct drm_framebuffer *fb = plane_state->fb;
> @@ -119,6 +254,7 @@ static void drm_gem_cleanup_shadow_fb(struct drm_plane
> *plane, struct drm_plane_
> drm_gem_vunmap(obj, &shadow_plane_state->map[i]);
> }
> }
> +EXPORT_SYMBOL(drm_gem_cleanup_shadow_fb);
>
> /**
> * drm_gem_simple_kms_prepare_shadow_fb - prepares shadow framebuffers
> diff --git a/include/drm/drm_gem_atomic_helper.h
> b/include/drm/drm_gem_atomic_helper.h
> index 08b96ccea325..7abf40bdab3d 100644
> --- a/include/drm/drm_gem_atomic_helper.h
> +++ b/include/drm/drm_gem_atomic_helper.h
> @@ -45,6 +45,38 @@ to_drm_shadow_plane_state(struct drm_plane_state *state)
> return container_of(state, struct drm_shadow_plane_state, base);
> }
>
> +void drm_gem_reset_shadow_plane(struct drm_plane *plane);
> +struct drm_plane_state *drm_gem_duplicate_shadow_plane_state(struct
> drm_plane *plane);
> +void drm_gem_destroy_shadow_plane_state(struct drm_plane *plane,
> + struct drm_plane_state *plane_state);
> +
> +/**
> + * DRM_GEM_SHADOW_PLANE_FUNCS -
> + * Initializes struct drm_plane_funcs for shadow-buffered planes
> + *
> + * Drivers may use GEM BOs as shadow buffers over the framebuffer memory.
> This
> + * macro initializes struct drm_plane_funcs to use the rsp helper functions.
> + */
> +#define DRM_GEM_SHADOW_PLANE_FUNCS \
> + .reset = drm_gem_reset_shadow_plane, \
> + .atomic_duplicate_state = drm_gem_duplicate_shadow_plane_state, \
> + .atomic_destroy_state = drm_gem_destroy_shadow_plane_state
> +
> +int drm_gem_prepare_shadow_fb(struct drm_plane *plane, struct
> drm_plane_state *plane_state);
> +void drm_gem_cleanup_shadow_fb(struct drm_plane *plane, struct
> drm_plane_state *plane_state);
> +
> +/**
> + * DRM_GEM_SHADOW_PLANE_HELPER_FUNCS -
> + * Initializes struct drm_plane_helper_funcs for shadow-buffered planes
> + *
> + * Drivers may use GEM BOs as shadow buffers over the framebuffer memory.
> This
> + * macro initializes struct drm_plane_helper_funcs to use the rsp helper
> + * functions.
> + */
> +#define DRM_GEM_SHADOW_PLANE_HELPER_FUNCS \
> + .prepare_fb = drm_gem_prepare_shadow_fb, \
> + .cleanup_fb = drm_gem_cleanup_shadow_fb
> +
> int drm_gem_simple_kms_prepare_shadow_fb(struct drm_simple_display_pipe
> *pipe,
> struct drm_plane_state *plane_state);
> void drm_gem_simple_kms_cleanup_shadow_fb(struct drm_simple_display_pipe
> *pipe,
Very nice and thoroughly explained docs!
Thanks, Reviewed-by: Daniel Vetter <daniel.vet...@ffwll.ch>
> --
> 2.30.0
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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