drm/ast: astdp: Store mode index in connector state

Look up the mode index for the astdp transmitter ship in the encoder's
atomic check and report an error if the display mode is not supported.

The lookup uses the DRM display mode instead of the driver's internal
VBIOS mode. Both are equivalent. The modesetting code later reads
the calculated index from the connector state to avoid recalculating it.

v2:
- fix typo in commit message (Jocelyn)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250204133209.403327-4-tzimmermann@suse.de

Author: Thomas Zimmermann

drivers/gpu/drm/ast/ast_dp.c

@@ -5,6 +5,7 @@
 #include <linux/firmware.h>
 #include <linux/delay.h>
 
+#include <drm/drm_atomic.h>
 #include <drm/drm_atomic_state_helper.h>
 #include <drm/drm_edid.h>
 #include <drm/drm_modeset_helper_vtables.h>
@@ -44,6 +45,8 @@ static const struct ast_astdp_mode_index_table_entry ast_astdp_mode_index_table[
 
 struct ast_astdp_connector_state {
 	struct drm_connector_state base;
+
+	int mode_index;
 };
 
 static struct ast_astdp_connector_state *
@@ -305,14 +308,12 @@ static void ast_astdp_encoder_helper_atomic_mode_set(struct drm_encoder *encoder
 	struct ast_device *ast = to_ast_device(dev);
 	struct ast_crtc_state *ast_crtc_state = to_ast_crtc_state(crtc_state);
 	const struct ast_vbios_enhtable *vmode = ast_crtc_state->vmode;
-	int mode_index;
+	struct ast_astdp_connector_state *astdp_conn_state =
+		to_ast_astdp_connector_state(conn_state);
+	int mode_index = astdp_conn_state->mode_index;
 	u8 refresh_rate_index;
 	u8 vgacre0, vgacre1, vgacre2;
 
-	mode_index = ast_astdp_get_mode_index(vmode->hde, vmode->vde);
-	if (drm_WARN_ON(dev, mode_index < 0))
-		return;
-
 	if (drm_WARN_ON(dev, vmode->refresh_rate_index < 1 || vmode->refresh_rate_index > 255))
 		return;
 	refresh_rate_index = vmode->refresh_rate_index - 1;
@@ -368,10 +369,30 @@ static void ast_astdp_encoder_helper_atomic_disable(struct drm_encoder *encoder,
 	ast_dp_set_phy_sleep(ast, true);
 }
 
+static int ast_astdp_encoder_helper_atomic_check(struct drm_encoder *encoder,
+						 struct drm_crtc_state *crtc_state,
+						 struct drm_connector_state *conn_state)
+{
+	const struct drm_display_mode *mode = &crtc_state->mode;
+	struct ast_astdp_connector_state *astdp_conn_state =
+		to_ast_astdp_connector_state(conn_state);
+	int res;
+
+	if (drm_atomic_crtc_needs_modeset(crtc_state)) {
+		res = ast_astdp_get_mode_index(mode->hdisplay, mode->vdisplay);
+		if (res < 0)
+			return res;
+		astdp_conn_state->mode_index = res;
+	}
+
+	return 0;
+}
+
 static const struct drm_encoder_helper_funcs ast_astdp_encoder_helper_funcs = {
 	.atomic_mode_set = ast_astdp_encoder_helper_atomic_mode_set,
 	.atomic_enable = ast_astdp_encoder_helper_atomic_enable,
 	.atomic_disable = ast_astdp_encoder_helper_atomic_disable,
+	.atomic_check = ast_astdp_encoder_helper_atomic_check,
 };
 
 /*
@@ -459,7 +480,7 @@ static void ast_astdp_connector_reset(struct drm_connector *connector)
 static struct drm_connector_state *
 ast_astdp_connector_atomic_duplicate_state(struct drm_connector *connector)
 {
-	struct ast_astdp_connector_state *new_astdp_state;
+	struct ast_astdp_connector_state *new_astdp_state, *astdp_state;
 	struct drm_device *dev = connector->dev;
 
 	if (drm_WARN_ON(dev, !connector->state))
@@ -470,6 +491,10 @@ ast_astdp_connector_atomic_duplicate_state(struct drm_connector *connector)
 		return NULL;
 	__drm_atomic_helper_connector_duplicate_state(connector, &new_astdp_state->base);
 
+	astdp_state = to_ast_astdp_connector_state(connector->state);
+
+	new_astdp_state->mode_index = astdp_state->mode_index;
+
 	return &new_astdp_state->base;
 }