drm/nouveau/i2c: balance port acquire/release

This was a half-finished hack before, just enough to handle the shared
aux/i2c pad thing on G94 and up.

We got lucky with locking etc up until now, as this was (generally) all
protected by the DRM mode_config lock.  It's about to become a lot more
likely to hit the races.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/core/include/subdev/i2c.h

@@ -62,6 +62,8 @@ struct nouveau_i2c {
 
 	struct nouveau_i2c_port *(*find)(struct nouveau_i2c *, u8 index);
 	struct nouveau_i2c_port *(*find_type)(struct nouveau_i2c *, u16 type);
+	int  (*acquire)(struct nouveau_i2c_port *, unsigned long timeout);
+	void (*release)(struct nouveau_i2c_port *);
 	int (*identify)(struct nouveau_i2c *, int index,
 			const char *what, struct nouveau_i2c_board_info *,
 			bool (*match)(struct nouveau_i2c_port *,

drivers/gpu/drm/nouveau/core/subdev/i2c/aux.c

@@ -27,10 +27,14 @@
 int
 nv_rdaux(struct nouveau_i2c_port *port, u32 addr, u8 *data, u8 size)
 {
+	struct nouveau_i2c *i2c = nouveau_i2c(port);
 	if (port->func->aux) {
-		if (port->func->acquire)
-			port->func->acquire(port);
-		return port->func->aux(port, true, 9, addr, data, size);
+		int ret = i2c->acquire(port, 0);
+		if (ret == 0) {
+			ret = port->func->aux(port, true, 9, addr, data, size);
+			i2c->release(port);
+		}
+		return ret;
 	}
 	return -ENODEV;
 }
@@ -38,10 +42,14 @@ nv_rdaux(struct nouveau_i2c_port *port, u32 addr, u8 *data, u8 size)
 int
 nv_wraux(struct nouveau_i2c_port *port, u32 addr, u8 *data, u8 size)
 {
+	struct nouveau_i2c *i2c = nouveau_i2c(port);
 	if (port->func->aux) {
-		if (port->func->acquire)
-			port->func->acquire(port);
-		return port->func->aux(port, true, 8, addr, data, size);
+		int ret = i2c->acquire(port, 0);
+		if (ret == 0) {
+			ret = port->func->aux(port, true, 8, addr, data, size);
+			i2c->release(port);
+		}
+		return ret;
 	}
 	return -ENODEV;
 }
@@ -50,13 +58,16 @@ static int
 aux_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
 {
 	struct nouveau_i2c_port *port = adap->algo_data;
+	struct nouveau_i2c *i2c = nouveau_i2c(port);
 	struct i2c_msg *msg = msgs;
 	int ret, mcnt = num;
 
 	if (!port->func->aux)
 		return -ENODEV;
-	if ( port->func->acquire)
-		port->func->acquire(port);
+
+	ret = i2c->acquire(port, 0);
+	if (ret)
+		return ret;
 
 	while (mcnt--) {
 		u8 remaining = msg->len;
@@ -75,8 +86,10 @@ aux_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
 				cmd |= 4; /* MOT */
 
 			ret = port->func->aux(port, true, cmd, msg->addr, ptr, cnt);
-			if (ret < 0)
+			if (ret < 0) {
+				i2c->release(port);
 				return ret;
+			}
 
 			ptr += cnt;
 			remaining -= cnt;
@@ -85,6 +98,7 @@ aux_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
 		msg++;
 	}
 
+	i2c->release(port);
 	return num;
 }
 

drivers/gpu/drm/nouveau/core/subdev/i2c/base.c

@@ -47,9 +47,15 @@ nouveau_i2c_pre_xfer(struct i2c_adapter *adap)
 {
 	struct i2c_algo_bit_data *bit = adap->algo_data;
 	struct nouveau_i2c_port *port = bit->data;
-	if (port->func->acquire)
-		port->func->acquire(port);
-	return 0;
+	return nouveau_i2c(port)->acquire(port, bit->timeout);
+}
+
+static void
+nouveau_i2c_post_xfer(struct i2c_adapter *adap)
+{
+	struct i2c_algo_bit_data *bit = adap->algo_data;
+	struct nouveau_i2c_port *port = bit->data;
+	return nouveau_i2c(port)->release(port);
 }
 
 static void
@@ -130,6 +136,7 @@ nouveau_i2c_port_create_(struct nouveau_object *parent,
 		bit->timeout = usecs_to_jiffies(2200);
 		bit->data = port;
 		bit->pre_xfer = nouveau_i2c_pre_xfer;
+		bit->post_xfer = nouveau_i2c_post_xfer;
 		bit->setsda = nouveau_i2c_setsda;
 		bit->setscl = nouveau_i2c_setscl;
 		bit->getsda = nouveau_i2c_getsda;
@@ -194,6 +201,21 @@ nouveau_i2c_find_type(struct nouveau_i2c *i2c, u16 type)
 	return NULL;
 }
 
+static void
+nouveau_i2c_release(struct nouveau_i2c_port *port)
+{
+	if (port->func->release)
+		port->func->release(port);
+}
+
+static int
+nouveau_i2c_acquire(struct nouveau_i2c_port *port, unsigned long timeout)
+{
+	if (port->func->acquire)
+		port->func->acquire(port);
+	return 0;
+}
+
 static int
 nouveau_i2c_identify(struct nouveau_i2c *i2c, int index, const char *what,
 		     struct nouveau_i2c_board_info *info,
@@ -383,6 +405,8 @@ nouveau_i2c_create_(struct nouveau_object *parent,
 	nv_subdev(i2c)->intr = nouveau_i2c_intr;
 	i2c->find = nouveau_i2c_find;
 	i2c->find_type = nouveau_i2c_find_type;
+	i2c->acquire = nouveau_i2c_acquire;
+	i2c->release = nouveau_i2c_release;
 	i2c->identify = nouveau_i2c_identify;
 	INIT_LIST_HEAD(&i2c->ports);
 

drivers/gpu/drm/nouveau/core/subdev/i2c/bit.c

@@ -187,8 +187,9 @@ i2c_bit_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
 	struct i2c_msg *msg = msgs;
 	int ret = 0, mcnt = num;
 
-	if (port->func->acquire)
-		port->func->acquire(port);
+	ret = nouveau_i2c(port)->acquire(port, nsecs_to_jiffies(T_TIMEOUT));
+	if (ret)
+		return ret;
 
 	while (!ret && mcnt--) {
 		u8 remaining = msg->len;
@@ -210,6 +211,7 @@ i2c_bit_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
 	}
 
 	i2c_stop(port);
+	nouveau_i2c(port)->release(port);
 	return (ret < 0) ? ret : num;
 }
 #else