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SubjectRe: [PATCH 7/8] drm/sun4i: sun4i_layer: Add a custom atomic_check for the frontend
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On 13/12/2017 16:33, Maxime Ripard wrote:
> Now that we have everything in place, we can start enabling the frontend.
> This is more difficult than one would assume since there can only be one
> plane using the frontend per-backend.
>
> We therefore need to make sure that the userspace will not try to setup
> multiple planes using it, since that would be impossible. In order to
> prevent that, we can create an atomic_check callback that will check that
> only one plane will effectively make use of the frontend in a given
> configuration, and will toggle the switch in that plane state so that the
> proper setup function can do their role.
>
> Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
> ---
> drivers/gpu/drm/sun4i/sun4i_backend.c | 65 ++++++++++++++++++++++++++++-
> drivers/gpu/drm/sun4i/sun4i_backend.h | 2 +-
> 2 files changed, 67 insertions(+)
>
> diff --git a/drivers/gpu/drm/sun4i/sun4i_backend.c b/drivers/gpu/drm/sun4i/sun4i_backend.c
> index f1d19767c55d..a7b87a12990e 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_backend.c
> +++ b/drivers/gpu/drm/sun4i/sun4i_backend.c
> @@ -11,6 +11,7 @@
> */
>
> #include <drm/drmP.h>
> +#include <drm/drm_atomic.h>
> #include <drm/drm_atomic_helper.h>
> #include <drm/drm_crtc.h>
> #include <drm/drm_crtc_helper.h>
> @@ -271,6 +272,69 @@ int sun4i_backend_update_layer_buffer(struct sun4i_backend *backend,
> return 0;
> }
>
> +static bool sun4i_backend_plane_uses_scaler(struct drm_plane_state *state)
> +{
> + u16 src_h = state->src_h >> 16;
> + u16 src_w = state->src_w >> 16;
> +
> + DRM_DEBUG_DRIVER("Input size %dx%d, output size %dx%d\n",
> + src_w, src_h, state->crtc_w, state->crtc_h);
> +
> + if ((state->crtc_h != src_h) || (state->crtc_w != src_w))
> + return true;
> +
> + return false;
> +}
> +
> +static bool sun4i_backend_plane_uses_frontend(struct drm_plane_state *state)
> +{
> + struct sun4i_layer *layer = plane_to_sun4i_layer(state->plane);
> + struct sun4i_backend *backend = layer->backend;
> +
> + if (IS_ERR(backend->frontend))
> + return false;
> +
> + return sun4i_backend_plane_uses_scaler(state);
> +}
> +
> +static int sun4i_backend_atomic_check(struct sunxi_engine *engine,
> + struct drm_crtc_state *crtc_state)
> +{
> + struct drm_atomic_state *state = crtc_state->state;
> + struct drm_device *drm = state->dev;
> + struct drm_plane *plane;
> + unsigned int num_frontend_planes = 0;
> +
> + DRM_DEBUG_DRIVER("Starting checking our planes\n");
> +
> + if (!crtc_state->planes_changed)
> + return 0;
> +
> + drm_for_each_plane_mask(plane, drm, crtc_state->plane_mask) {
> + struct drm_plane_state *plane_state =
> + drm_atomic_get_plane_state(state, plane);
> + struct sun4i_layer_state *layer_state =
> + state_to_sun4i_layer_state(plane_state);
> +
> + if (sun4i_backend_plane_uses_frontend(plane_state)) {
> + DRM_DEBUG_DRIVER("Using the frontend for plane %d\n",
> + plane->index);
> +
> + layer_state->uses_frontend = true;
> + num_frontend_planes++;
> + } else {
> + layer_state->uses_frontend = false;
> + }
> + }
> +
> + if (num_frontend_planes > SUN4I_BACKEND_NUM_FRONTEND_LAYERS) {
> + DRM_DEBUG_DRIVER("Too many planes going through the frontend, rejecting\n");
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> static int sun4i_backend_init_sat(struct device *dev) {
> struct sun4i_backend *backend = dev_get_drvdata(dev);
> int ret;
> @@ -384,6 +448,7 @@ static struct sun4i_frontend *sun4i_backend_find_frontend(struct sun4i_drv *drv,
> }
>
> static const struct sunxi_engine_ops sun4i_backend_engine_ops = {
> + .atomic_check = sun4i_backend_atomic_check,
> .commit = sun4i_backend_commit,
> .layers_init = sun4i_layers_init,
> .apply_color_correction = sun4i_backend_apply_color_correction,
> diff --git a/drivers/gpu/drm/sun4i/sun4i_backend.h b/drivers/gpu/drm/sun4i/sun4i_backend.h
> index 636a51521e77..3b5531440fa3 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_backend.h
> +++ b/drivers/gpu/drm/sun4i/sun4i_backend.h
> @@ -144,6 +144,8 @@
> #define SUN4I_BACKEND_HWCCOLORTAB_OFF 0x4c00
> #define SUN4I_BACKEND_PIPE_OFF(p) (0x5000 + (0x400 * (p)))
>
> +#define SUN4I_BACKEND_NUM_FRONTEND_LAYERS 1
> +
> struct sun4i_backend {
> struct sunxi_engine engine;
> struct sun4i_frontend *frontend;
>

Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>

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