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From: Stephen Boyd <swboyd@chromium.org>
To: chrome-platform@lists.linux.dev
Cc: linux-kernel@vger.kernel.org,
	patches@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org,
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	Robert Foss <rfoss@kernel.org>,
	Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
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	Jernej Skrabec <jernej.skrabec@gmail.com>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <mripard@kernel.org>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	David Airlie <airlied@gmail.com>,
	Daniel Vetter <daniel@ffwll.ch>,
	dri-devel@lists.freedesktop.org
Subject: [PATCH 06/22] drm/bridge: Verify lane assignment is going to work during atomic_check
Date: Fri,  9 Feb 2024 23:09:17 -0800
Message-ID: <20240210070934.2549994-7-swboyd@chromium.org>
In-Reply-To: <20240210070934.2549994-1-swboyd@chromium.org>
References: <20240210070934.2549994-1-swboyd@chromium.org>
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Verify during drm_atomic_bridge_check() that the lane assignment set in
a bridge's atomic_check() callback is going to be satisfied by the
previous bridge. If the next bridge is requiring something besides the
default 1:1 lane assignment on its input then there must be an output
lane assignment on the previous bridge's output. Otherwise the next
bridge won't get the lanes assigned that it needs.

Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Cc: Neil Armstrong <neil.armstrong@linaro.org>
Cc: Robert Foss <rfoss@kernel.org>
Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
Cc: Jonas Karlman <jonas@kwiboo.se>
Cc: Jernej Skrabec <jernej.skrabec@gmail.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: <dri-devel@lists.freedesktop.org>
Cc: Pin-yen Lin <treapking@chromium.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
---
 drivers/gpu/drm/drm_bridge.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index 3fce0d8d7dcb..5097e7c65ddf 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -881,6 +881,10 @@ static int drm_atomic_bridge_check(struct drm_bridge *bridge,
 				   struct drm_crtc_state *crtc_state,
 				   struct drm_connector_state *conn_state)
 {
+	u8 num_input_lanes, num_output_lanes = 0;
+	const struct drm_lane_cfg *input_lanes;
+	int i;
+
 	if (bridge->funcs->atomic_check) {
 		struct drm_bridge_state *bridge_state;
 		int ret;
@@ -894,12 +898,24 @@ static int drm_atomic_bridge_check(struct drm_bridge *bridge,
 						  crtc_state, conn_state);
 		if (ret)
 			return ret;
+		num_output_lanes = bridge_state->output_bus_cfg.num_lanes;
 	} else if (bridge->funcs->mode_fixup) {
 		if (!bridge->funcs->mode_fixup(bridge, &crtc_state->mode,
 					       &crtc_state->adjusted_mode))
 			return -EINVAL;
 	}
 
+	input_lanes = drm_bridge_next_bridge_lane_cfg(bridge,
+						      crtc_state->state,
+						      &num_input_lanes);
+	/*
+	 * Ensure this bridge is aware that the next bridge wants to
+	 * reassign lanes.
+	 */
+	for (i = 0; i < num_input_lanes; i++)
+		if (i != input_lanes[i].logical && !num_output_lanes)
+			return -ENOTSUPP;
+
 	return 0;
 }
 
-- 
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