linux-kernel - [PATCH v7 1/9] drm/omap: add sanity plane state check

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Date:   Wed, 17 Nov 2021 15:19:20 +0100
From:   Neil Armstrong <narmstrong@...libre.com>
To:     tomba@...nel.org
Cc:     linux-omap@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, khilman@...libre.com,
        Neil Armstrong <narmstrong@...libre.com>,
        Benoit Parrot <bparrot@...com>,
        Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Subject: [PATCH v7 1/9] drm/omap: add sanity plane state check

Call drm_atomic_helper_check_plane_state() from the plane
atomic_check() callback in order to add plane state sanity
checking.

It will permit filtering out totally bad scaling factors, even
if the real check are done later in the atomic commit.

Calling drm_atomic_helper_check_plane_state() also sets
plane_state->visible which will be useful when dynamically
assigning hw overlays to planes.

Signed-off-by: Benoit Parrot <bparrot@...com>
Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
---
 drivers/gpu/drm/omapdrm/omap_plane.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/gpu/drm/omapdrm/omap_plane.c b/drivers/gpu/drm/omapdrm/omap_plane.c
index 512af976b7e9..c3de4f339387 100644
--- a/drivers/gpu/drm/omapdrm/omap_plane.c
+++ b/drivers/gpu/drm/omapdrm/omap_plane.c
@@ -104,12 +104,15 @@ static void omap_plane_atomic_disable(struct drm_plane *plane,
 	dispc_ovl_enable(priv->dispc, omap_plane->id, false);
 }
 
+#define FRAC_16_16(mult, div)    (((mult) << 16) / (div))
+
 static int omap_plane_atomic_check(struct drm_plane *plane,
 				   struct drm_atomic_state *state)
 {
 	struct drm_plane_state *new_plane_state = drm_atomic_get_new_plane_state(state,
 										 plane);
 	struct drm_crtc_state *crtc_state;
+	int ret;
 
 	if (!new_plane_state->fb)
 		return 0;
@@ -127,6 +130,18 @@ static int omap_plane_atomic_check(struct drm_plane *plane,
 	if (!crtc_state->enable)
 		return 0;
 
+	/*
+	 * Note: these are just sanity checks to filter out totally bad scaling
+	 * factors. The real limits must be calculated case by case, and
+	 * unfortunately we currently do those checks only at the commit
+	 * phase in dispc.
+	 */
+	ret = drm_atomic_helper_check_plane_state(new_plane_state, crtc_state,
+						  FRAC_16_16(1, 8), FRAC_16_16(8, 1),
+						  true, true);
+	if (ret)
+		return ret;
+
 	if (new_plane_state->crtc_x < 0 || new_plane_state->crtc_y < 0)
 		return -EINVAL;
 
-- 
2.25.1