linux-kernel - [PATCH v4 02/18] drm/bridge: Verify lane assignment is going to work during atomic

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Message-ID: <20240901040658.157425-3-swboyd@chromium.org>
Date: Sat, 31 Aug 2024 21:06:40 -0700
From: Stephen Boyd <swboyd@...omium.org>
To: chrome-platform@...ts.linux.dev
Cc: linux-kernel@...r.kernel.org,
	patches@...ts.linux.dev,
	devicetree@...r.kernel.org,
	Douglas Anderson <dianders@...omium.org>,
	Pin-yen Lin <treapking@...omium.org>,
	Andrzej Hajda <andrzej.hajda@...el.com>,
	Benson Leung <bleung@...omium.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Daniel Vetter <daniel@...ll.ch>,
	David Airlie <airlied@...il.com>,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	dri-devel@...ts.freedesktop.org,
	Guenter Roeck <groeck@...omium.org>,
	Jernej Skrabec <jernej.skrabec@...il.com>,
	Jonas Karlman <jonas@...boo.se>,
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	Maxime Ripard <mripard@...nel.org>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Prashant Malani <pmalani@...omium.org>,
	Robert Foss <rfoss@...nel.org>,
	Rob Herring <robh+dt@...nel.org>,
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	Vinod Koul <vkoul@...nel.org>
Subject: [PATCH v4 02/18] drm/bridge: Verify lane assignment is going to work during atomic_check

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@...el.com>
Cc: Neil Armstrong <neil.armstrong@...aro.org>
Cc: Robert Foss <rfoss@...nel.org>
Cc: Laurent Pinchart <Laurent.pinchart@...asonboard.com>
Cc: Jonas Karlman <jonas@...boo.se>
Cc: Jernej Skrabec <jernej.skrabec@...il.com>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
Cc: Maxime Ripard <mripard@...nel.org>
Cc: Thomas Zimmermann <tzimmermann@...e.de>
Cc: David Airlie <airlied@...il.com>
Cc: Daniel Vetter <daniel@...ll.ch>
Cc: <dri-devel@...ts.freedesktop.org>
Cc: Pin-yen Lin <treapking@...omium.org>
Cc: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Signed-off-by: Stephen Boyd <swboyd@...omium.org>
---
 drivers/gpu/drm/drm_bridge.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index bd18c1e91dee..e350248ba5c2 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -860,6 +860,10 @@ 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;
+	unsigned int i;
+
 	if (bridge->funcs->atomic_check) {
 		struct drm_bridge_state *bridge_state;
 		int ret;
@@ -873,12 +877,25 @@ 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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