drm/nouveau/i2c: resume use of i2c-algo-bit, rather than custom stack

Previous issues with i2c-algo-bit have now been resolved.

This is a revert of f553b79c mostly,
due to fixes in the i2c core repairing the original issue, this code
isn't required and was causing regressions.
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>
Reported-by: NNick Bowler <nbowler@elliptictech.com>
Tested-by: NNick Bowler <nbowler@elliptictech.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

drivers/gpu/drm/nouveau/nouveau_i2c.c

@@ -29,10 +29,6 @@
 #include "nouveau_i2c.h"
 #include "nouveau_hw.h"
 
-#define T_TIMEOUT  2200000
-#define T_RISEFALL 1000
-#define T_HOLD     5000
-
 static void
 i2c_drive_scl(void *data, int state)
 {
@@ -113,175 +109,6 @@ i2c_sense_sda(void *data)
 	return 0;
 }
 
-static void
-i2c_delay(struct nouveau_i2c_chan *port, u32 nsec)
-{
-	udelay((nsec + 500) / 1000);
-}
-
-static bool
-i2c_raise_scl(struct nouveau_i2c_chan *port)
-{
-	u32 timeout = T_TIMEOUT / T_RISEFALL;
-
-	i2c_drive_scl(port, 1);
-	do {
-		i2c_delay(port, T_RISEFALL);
-	} while (!i2c_sense_scl(port) && --timeout);
-
-	return timeout != 0;
-}
-
-static int
-i2c_start(struct nouveau_i2c_chan *port)
-{
-	int ret = 0;
-
-	port->state  = i2c_sense_scl(port);
-	port->state |= i2c_sense_sda(port) << 1;
-	if (port->state != 3) {
-		i2c_drive_scl(port, 0);
-		i2c_drive_sda(port, 1);
-		if (!i2c_raise_scl(port))
-			ret = -EBUSY;
-	}
-
-	i2c_drive_sda(port, 0);
-	i2c_delay(port, T_HOLD);
-	i2c_drive_scl(port, 0);
-	i2c_delay(port, T_HOLD);
-	return ret;
-}
-
-static void
-i2c_stop(struct nouveau_i2c_chan *port)
-{
-	i2c_drive_scl(port, 0);
-	i2c_drive_sda(port, 0);
-	i2c_delay(port, T_RISEFALL);
-
-	i2c_drive_scl(port, 1);
-	i2c_delay(port, T_HOLD);
-	i2c_drive_sda(port, 1);
-	i2c_delay(port, T_HOLD);
-}
-
-static int
-i2c_bitw(struct nouveau_i2c_chan *port, int sda)
-{
-	i2c_drive_sda(port, sda);
-	i2c_delay(port, T_RISEFALL);
-
-	if (!i2c_raise_scl(port))
-		return -ETIMEDOUT;
-	i2c_delay(port, T_HOLD);
-
-	i2c_drive_scl(port, 0);
-	i2c_delay(port, T_HOLD);
-	return 0;
-}
-
-static int
-i2c_bitr(struct nouveau_i2c_chan *port)
-{
-	int sda;
-
-	i2c_drive_sda(port, 1);
-	i2c_delay(port, T_RISEFALL);
-
-	if (!i2c_raise_scl(port))
-		return -ETIMEDOUT;
-	i2c_delay(port, T_HOLD);
-
-	sda = i2c_sense_sda(port);
-
-	i2c_drive_scl(port, 0);
-	i2c_delay(port, T_HOLD);
-	return sda;
-}
-
-static int
-i2c_get_byte(struct nouveau_i2c_chan *port, u8 *byte, bool last)
-{
-	int i, bit;
-
-	*byte = 0;
-	for (i = 7; i >= 0; i--) {
-		bit = i2c_bitr(port);
-		if (bit < 0)
-			return bit;
-		*byte |= bit << i;
-	}
-
-	return i2c_bitw(port, last ? 1 : 0);
-}
-
-static int
-i2c_put_byte(struct nouveau_i2c_chan *port, u8 byte)
-{
-	int i, ret;
-	for (i = 7; i >= 0; i--) {
-		ret = i2c_bitw(port, !!(byte & (1 << i)));
-		if (ret < 0)
-			return ret;
-	}
-
-	ret = i2c_bitr(port);
-	if (ret == 1) /* nack */
-		ret = -EIO;
-	return ret;
-}
-
-static int
-i2c_addr(struct nouveau_i2c_chan *port, struct i2c_msg *msg)
-{
-	u32 addr = msg->addr << 1;
-	if (msg->flags & I2C_M_RD)
-		addr |= 1;
-	return i2c_put_byte(port, addr);
-}
-
-static int
-i2c_bit_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
-{
-	struct nouveau_i2c_chan *port = (struct nouveau_i2c_chan *)adap;
-	struct i2c_msg *msg = msgs;
-	int ret = 0, mcnt = num;
-
-	while (!ret && mcnt--) {
-		u8 remaining = msg->len;
-		u8 *ptr = msg->buf;
-
-		ret = i2c_start(port);
-		if (ret == 0)
-			ret = i2c_addr(port, msg);
-
-		if (msg->flags & I2C_M_RD) {
-			while (!ret && remaining--)
-				ret = i2c_get_byte(port, ptr++, !remaining);
-		} else {
-			while (!ret && remaining--)
-				ret = i2c_put_byte(port, *ptr++);
-		}
-
-		msg++;
-	}
-
-	i2c_stop(port);
-	return (ret < 0) ? ret : num;
-}
-
-static u32
-i2c_bit_func(struct i2c_adapter *adap)
-{
-	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
-}
-
-const struct i2c_algorithm nouveau_i2c_bit_algo = {
-	.master_xfer = i2c_bit_xfer,
-	.functionality = i2c_bit_func
-};
-
 static const uint32_t nv50_i2c_port[] = {
 	0x00e138, 0x00e150, 0x00e168, 0x00e180,
 	0x00e254, 0x00e274, 0x00e764, 0x00e780,
@@ -384,12 +211,10 @@ nouveau_i2c_init(struct drm_device *dev)
 		case 0: /* NV04:NV50 */
 			port->drive = entry[0];
 			port->sense = entry[1];
-			port->adapter.algo = &nouveau_i2c_bit_algo;
 			break;
 		case 4: /* NV4E */
 			port->drive = 0x600800 + entry[1];
 			port->sense = port->drive;
-			port->adapter.algo = &nouveau_i2c_bit_algo;
 			break;
 		case 5: /* NV50- */
 			port->drive = entry[0] & 0x0f;
@@ -402,7 +227,6 @@ nouveau_i2c_init(struct drm_device *dev)
 				port->drive = 0x00d014 + (port->drive * 0x20);
 				port->sense = port->drive;
 			}
-			port->adapter.algo = &nouveau_i2c_bit_algo;
 			break;
 		case 6: /* NV50- DP AUX */
 			port->drive = entry[0];
@@ -413,7 +237,7 @@ nouveau_i2c_init(struct drm_device *dev)
 			break;
 		}
 
-		if (!port->adapter.algo) {
+		if (!port->adapter.algo && !port->drive) {
 			NV_ERROR(dev, "I2C%d: type %d index %x/%x unknown\n",
 				 i, port->type, port->drive, port->sense);
 			kfree(port);
@@ -429,7 +253,26 @@ nouveau_i2c_init(struct drm_device *dev)
 		port->dcb = ROM32(entry[0]);
 		i2c_set_adapdata(&port->adapter, i2c);
 
+		if (port->adapter.algo != &nouveau_dp_i2c_algo) {
+			port->adapter.algo_data = &port->bit;
+			port->bit.udelay = 10;
+			port->bit.timeout = usecs_to_jiffies(2200);
+			port->bit.data = port;
+			port->bit.setsda = i2c_drive_sda;
+			port->bit.setscl = i2c_drive_scl;
+			port->bit.getsda = i2c_sense_sda;
+			port->bit.getscl = i2c_sense_scl;
+
+			i2c_drive_scl(port, 0);
+			i2c_drive_sda(port, 1);
+			i2c_drive_scl(port, 1);
+
+			ret = i2c_bit_add_bus(&port->adapter);
+		} else {
+			port->adapter.algo = &nouveau_dp_i2c_algo;
 			ret = i2c_add_adapter(&port->adapter);
+		}
+
 		if (ret) {
 			NV_ERROR(dev, "I2C%d: failed register: %d\n", i, ret);
 			kfree(port);

drivers/gpu/drm/nouveau/nouveau_i2c.h

@@ -34,6 +34,7 @@
 struct nouveau_i2c_chan {
 	struct i2c_adapter adapter;
 	struct drm_device *dev;
+	struct i2c_algo_bit_data bit;
 	struct list_head head;
 	u8  index;
 	u8  type;