From: Jernej Skrabec <jernej.skrabec@siol.net>
Date: Wed, 11 Jul 2018 13:27:06 +0200
Subject: drm/sun4i: mixer: Read id from DT
Git-commit: 7da9b2e47fefb419a21e1c4c5a0682846b41b4a0
Patch-mainline: v4.19-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

Currently, TCON supports 2 ways to match TCON with engine (mixer in this
case). Old way is to just traverse of graph backwards and compare node
pointer. New way is to match TCON and engine by their respective ids.
All SoCs with DE2 enabled till now used the old way, which means mixer
id was never used and thus never implemented.

However, for R40, only the new way will be used. To prepare for that,
implement mixer id fetching from DT.

Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180711112706.30222-1-jernej.skrabec@siol.net

Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/sun4i/sun8i_mixer.c |   49 ++++++++++++++++++++++++++++++++++--
 1 file changed, 47 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/sun4i/sun8i_mixer.c
+++ b/drivers/gpu/drm/sun4i/sun8i_mixer.c
@@ -22,6 +22,7 @@
 #include <linux/component.h>
 #include <linux/dma-mapping.h>
 #include <linux/of_device.h>
+#include <linux/of_graph.h>
 #include <linux/reset.h>
 
 #include "sun4i_drv.h"
@@ -322,6 +323,42 @@ static struct regmap_config sun8i_mixer_
 	.max_register	= 0xbfffc, /* guessed */
 };
 
+static int sun8i_mixer_of_get_id(struct device_node *node)
+{
+	struct device_node *port, *ep;
+	int ret = -EINVAL;
+
+	/* output is port 1 */
+	port = of_graph_get_port_by_id(node, 1);
+	if (!port)
+		return -EINVAL;
+
+	/* try to find downstream endpoint */
+	for_each_available_child_of_node(port, ep) {
+		struct device_node *remote;
+		u32 reg;
+
+		remote = of_graph_get_remote_endpoint(ep);
+		if (!remote)
+			continue;
+
+		ret = of_property_read_u32(remote, "reg", &reg);
+		if (!ret) {
+			of_node_put(remote);
+			of_node_put(ep);
+			of_node_put(port);
+
+			return reg;
+		}
+
+		of_node_put(remote);
+	}
+
+	of_node_put(port);
+
+	return ret;
+}
+
 static int sun8i_mixer_bind(struct device *dev, struct device *master,
 			      void *data)
 {
@@ -353,8 +390,16 @@ static int sun8i_mixer_bind(struct devic
 	dev_set_drvdata(dev, mixer);
 	mixer->engine.ops = &sun8i_engine_ops;
 	mixer->engine.node = dev->of_node;
-	/* The ID of the mixer currently doesn't matter */
-	mixer->engine.id = -1;
+
+	/*
+	 * While this function can fail, we shouldn't do anything
+	 * if this happens. Some early DE2 DT entries don't provide
+	 * mixer id but work nevertheless because matching between
+	 * TCON and mixer is done by comparing node pointers (old
+	 * way) instead comparing ids. If this function fails and
+	 * id is needed, it will fail during id matching anyway.
+	 */
+	mixer->engine.id = sun8i_mixer_of_get_id(dev->of_node);
 
 	mixer->cfg = of_device_get_match_data(dev);
 	if (!mixer->cfg)