i2c: mvtwsi: Make delay times frequency-dependent

Some devices using the MVTWSI driver have the option to run at speeds
faster than Standard Mode (100kHZ). On the Armada 38x controllers, this
is actually necessary, since due to erratum FE-8471889, a timing
violation concerning repeated starts prevents the controller from
working correctly in Standard Mode. One of the workarounds recommended
in the erratum is to set the bus to Fast Mode (400kHZ) operation and
ensure all connected devices are set to Fast Mode.

In the current version of the driver, however, the delay times are
hard-coded to 10ms, corresponding to Standard Mode operation. To take
full advantage of the faster modes, we would need to either keep the
currently configured I2C speed in a globally accessible variable, or
pass it to the necessary functions as a parameter. For DM, the first
option is not a problem, and we can simply keep the speed in the private
data of the driver. For the legacy interface, however, we would need to
introduce a static variable, which would cause problems with boots from
NOR flashes; see commit d6b7757 "i2c: mvtwsi: Eliminate
twsi_control_flags."

As to not clutter the interface with yet another parameter, we therefore
keep the default 10ms delays for the legacy functions.

In DM mode, we make the delay time dependant on the frequency to allow
taking full advantage of faster modes of operation (tested with up to
1MHZ frequency on Armada MV88F6820).

Signed-off-by: Mario Six <mario.six@gdsys.cc>
Reviewed-by: Stefan Roese <sr@denx.de>

drivers/i2c/mvtwsi.c

@@ -12,6 +12,7 @@
 #include <i2c.h>
 #include <asm/errno.h>
 #include <asm/io.h>
+#include <linux/compat.h>
 #ifdef CONFIG_DM_I2C
 #include <dm.h>
 #endif
@@ -78,6 +79,8 @@ struct mvtwsi_i2c_dev {
 	u8 slaveadd;
 	/* The configured I2C speed in Hz */
 	uint speed;
+	/* The current length of a clock period (depending on speed) */
+	uint tick;
 };
 #endif /* CONFIG_DM_I2C */
 
@@ -154,7 +157,15 @@ enum mvtwsi_ack_flags {
 	MVTWSI_READ_ACK = 1,
 };
 
+inline uint calc_tick(uint speed)
+{
+	/* One tick = the duration of a period at the specified speed in ns (we
+	 * add 100 ns to be on the safe side) */
+	return (1000000000u / speed) + 100;
+}
+
 #ifndef CONFIG_DM_I2C
+
 /*
  * MVTWSI controller base
  */
@@ -230,7 +241,8 @@ inline uint mvtwsi_error(uint ec, uint lc, uint ls, uint es)
  * Wait for IFLG to raise, or return 'timeout.' Then, if the status is as
  * expected, return 0 (ok) or 'wrong status' otherwise.
  */
-static int twsi_wait(struct mvtwsi_registers *twsi, int expected_status)
+static int twsi_wait(struct mvtwsi_registers *twsi, int expected_status,
+		     uint tick)
 {
 	int control, status;
 	int timeout = 1000;
@@ -246,7 +258,7 @@ static int twsi_wait(struct mvtwsi_registers *twsi, int expected_status)
 					MVTWSI_ERROR_WRONG_STATUS,
 					control, status, expected_status);
 		}
-		udelay(10); /* One clock cycle at 100 kHz */
+		ndelay(tick); /* One clock cycle */
 	} while (timeout--);
 	status = readl(&twsi->status);
 	return mvtwsi_error(MVTWSI_ERROR_TIMEOUT, control, status,
@@ -257,20 +269,21 @@ static int twsi_wait(struct mvtwsi_registers *twsi, int expected_status)
  * Assert the START condition, either in a single I2C transaction
  * or inside back-to-back ones (repeated starts).
  */
-static int twsi_start(struct mvtwsi_registers *twsi, int expected_status)
+static int twsi_start(struct mvtwsi_registers *twsi, int expected_status,
+		      uint tick)
 {
 	/* Assert START */
 	writel(MVTWSI_CONTROL_TWSIEN | MVTWSI_CONTROL_START |
 	       MVTWSI_CONTROL_CLEAR_IFLG, &twsi->control);
 	/* Wait for controller to process START */
-	return twsi_wait(twsi, expected_status);
+	return twsi_wait(twsi, expected_status, tick);
 }
 
 /*
  * Send a byte (i2c address or data).
  */
 static int twsi_send(struct mvtwsi_registers *twsi, u8 byte,
-		     int expected_status)
+		     int expected_status, uint tick)
 {
 	/* Write byte to data register for sending */
 	writel(byte, &twsi->data);
@@ -278,13 +291,14 @@ static int twsi_send(struct mvtwsi_registers *twsi, u8 byte,
 	writel(MVTWSI_CONTROL_TWSIEN | MVTWSI_CONTROL_CLEAR_IFLG,
 	       &twsi->control);
 	/* Wait for controller to receive byte, and check ACK */
-	return twsi_wait(twsi, expected_status);
+	return twsi_wait(twsi, expected_status, tick);
 }
 
 /*
  * Receive a byte.
  */
-static int twsi_recv(struct mvtwsi_registers *twsi, u8 *byte, int ack_flag)
+static int twsi_recv(struct mvtwsi_registers *twsi, u8 *byte, int ack_flag,
+		     uint tick)
 {
 	int expected_status, status, control;
 
@@ -296,7 +310,7 @@ static int twsi_recv(struct mvtwsi_registers *twsi, u8 *byte, int ack_flag)
 	control |= ack_flag == MVTWSI_READ_ACK ? MVTWSI_CONTROL_ACK : 0;
 	writel(control | MVTWSI_CONTROL_CLEAR_IFLG, &twsi->control);
 	/* Wait for controller to receive byte, and assert ACK or NAK */
-	status = twsi_wait(twsi, expected_status);
+	status = twsi_wait(twsi, expected_status, tick);
 	/* If we did receive the expected byte, store it */
 	if (status == 0)
 		*byte = readl(&twsi->data);
@@ -307,7 +321,7 @@ static int twsi_recv(struct mvtwsi_registers *twsi, u8 *byte, int ack_flag)
  * Assert the STOP condition.
  * This is also used to force the bus back to idle (SDA = SCL = 1).
  */
-static int twsi_stop(struct mvtwsi_registers *twsi)
+static int twsi_stop(struct mvtwsi_registers *twsi, uint tick)
 {
 	int control, stop_status;
 	int status = 0;
@@ -321,7 +335,7 @@ static int twsi_stop(struct mvtwsi_registers *twsi)
 		stop_status = readl(&twsi->status);
 		if (stop_status == MVTWSI_STATUS_IDLE)
 			break;
-		udelay(10); /* One clock cycle at 100 kHz */
+		ndelay(tick); /* One clock cycle */
 	} while (timeout--);
 	control = readl(&twsi->control);
 	if (stop_status != MVTWSI_STATUS_IDLE)
@@ -376,21 +390,32 @@ static uint __twsi_i2c_set_bus_speed(struct mvtwsi_registers *twsi,
 		}
 	}
 	writel(baud, &twsi->baudrate);
-	return 0;
+
+	/* Wait for controller for one tick */
+#ifdef CONFIG_DM_I2C
+	ndelay(calc_tick(highest_speed));
+#else
+	ndelay(10000);
+#endif
+	return highest_speed;
 }
 
 static void __twsi_i2c_init(struct mvtwsi_registers *twsi, int speed,
-			    int slaveadd)
+			    int slaveadd, uint *actual_speed)
 {
 	/* Reset controller */
 	twsi_reset(twsi);
 	/* Set speed */
-	__twsi_i2c_set_bus_speed(twsi, speed);
+	*actual_speed = __twsi_i2c_set_bus_speed(twsi, speed);
 	/* Set slave address; even though we don't use it */
 	writel(slaveadd, &twsi->slave_address);
 	writel(0, &twsi->xtnd_slave_addr);
 	/* Assert STOP, but don't care for the result */
-	(void) twsi_stop(twsi);
+#ifdef CONFIG_DM_I2C
+	(void) twsi_stop(twsi, calc_tick(*actual_speed));
+#else
+	(void) twsi_stop(twsi, 10000);
+#endif
 }
 
 /*
@@ -398,7 +423,7 @@ static void __twsi_i2c_init(struct mvtwsi_registers *twsi, int speed,
  * Expected address status will derive from direction bit (bit 0) in addr.
  */
 static int i2c_begin(struct mvtwsi_registers *twsi, int expected_start_status,
-		     u8 addr)
+		     u8 addr, uint tick)
 {
 	int status, expected_addr_status;
 
@@ -409,10 +434,10 @@ static int i2c_begin(struct mvtwsi_registers *twsi, int expected_start_status,
 	else /* Writing */
 		expected_addr_status = MVTWSI_STATUS_ADDR_W_ACK;
 	/* Assert START */
-	status = twsi_start(twsi, expected_start_status);
+	status = twsi_start(twsi, expected_start_status, tick);
 	/* Send out the address if the start went well */
 	if (status == 0)
-		status = twsi_send(twsi, addr, expected_addr_status);
+		status = twsi_send(twsi, addr, expected_addr_status, tick);
 	/* Return 0, or the status of the first failure */
 	return status;
 }
@@ -420,18 +445,19 @@ static int i2c_begin(struct mvtwsi_registers *twsi, int expected_start_status,
 /*
  * Begin read, nak data byte, end.
  */
-static int __twsi_i2c_probe_chip(struct mvtwsi_registers *twsi, uchar chip)
+static int __twsi_i2c_probe_chip(struct mvtwsi_registers *twsi, uchar chip,
+				 uint tick)
 {
 	u8 dummy_byte;
 	int status;
 
 	/* Begin i2c read */
-	status = i2c_begin(twsi, MVTWSI_STATUS_START, (chip << 1) | 1);
+	status = i2c_begin(twsi, MVTWSI_STATUS_START, (chip << 1) | 1, tick);
 	/* Dummy read was accepted: receive byte, but NAK it. */
 	if (status == 0)
-		status = twsi_recv(twsi, &dummy_byte, MVTWSI_READ_NAK);
+		status = twsi_recv(twsi, &dummy_byte, MVTWSI_READ_NAK, tick);
 	/* Stop transaction */
-	twsi_stop(twsi);
+	twsi_stop(twsi, tick);
 	/* Return 0, or the status of the first failure */
 	return status;
 }
@@ -445,7 +471,8 @@ static int __twsi_i2c_probe_chip(struct mvtwsi_registers *twsi, uchar chip)
  * will be a repeated start without a preceding stop.
  */
 static int __twsi_i2c_read(struct mvtwsi_registers *twsi, uchar chip,
-			   u8 *addr, int alen, uchar *data, int length)
+			   u8 *addr, int alen, uchar *data, int length,
+			   uint tick)
 {
 	int status = 0;
 	int stop_status;
@@ -453,25 +480,25 @@ static int __twsi_i2c_read(struct mvtwsi_registers *twsi, uchar chip,
 
 	if (alen > 0) {
 		/* Begin i2c write to send the address bytes */
-		status = i2c_begin(twsi, expected_start, (chip << 1));
+		status = i2c_begin(twsi, expected_start, (chip << 1), tick);
 		/* Send address bytes */
 		while ((status == 0) && alen--)
 			status = twsi_send(twsi, *(addr++),
-					   MVTWSI_STATUS_DATA_W_ACK);
+					   MVTWSI_STATUS_DATA_W_ACK, tick);
 		/* Send repeated STARTs after the initial START */
 		expected_start = MVTWSI_STATUS_REPEATED_START;
 	}
 	/* Begin i2c read to receive data bytes */
 	if (status == 0)
-		status = i2c_begin(twsi, expected_start, (chip << 1) | 1);
+		status = i2c_begin(twsi, expected_start, (chip << 1) | 1, tick);
 	/* Receive actual data bytes; set NAK if we if we have nothing more to
 	 * read */
 	while ((status == 0) && length--)
 		status = twsi_recv(twsi, data++,
 				   length > 0 ?
-				   MVTWSI_READ_ACK : MVTWSI_READ_NAK);
+				   MVTWSI_READ_ACK : MVTWSI_READ_NAK, tick);
 	/* Stop transaction */
-	stop_status = twsi_stop(twsi);
+	stop_status = twsi_stop(twsi, tick);
 	/* Return 0, or the status of the first failure */
 	return status != 0 ? status : stop_status;
 }
@@ -480,21 +507,24 @@ static int __twsi_i2c_read(struct mvtwsi_registers *twsi, uchar chip,
  * Begin write, send address byte(s), send data bytes, end.
  */
 static int __twsi_i2c_write(struct mvtwsi_registers *twsi, uchar chip,
-			    u8 *addr, int alen, uchar *data, int length)
+			    u8 *addr, int alen, uchar *data, int length,
+			    uint tick)
 {
 	int status, stop_status;
 
 	/* Begin i2c write to send first the address bytes, then the
 	 * data bytes */
-	status = i2c_begin(twsi, MVTWSI_STATUS_START, (chip << 1));
+	status = i2c_begin(twsi, MVTWSI_STATUS_START, (chip << 1), tick);
 	/* Send address bytes */
 	while ((status == 0) && (alen-- > 0))
-		status = twsi_send(twsi, *(addr++), MVTWSI_STATUS_DATA_W_ACK);
+		status = twsi_send(twsi, *(addr++), MVTWSI_STATUS_DATA_W_ACK,
+				   tick);
 	/* Send data bytes */
 	while ((status == 0) && (length-- > 0))
-		status = twsi_send(twsi, *(data++), MVTWSI_STATUS_DATA_W_ACK);
+		status = twsi_send(twsi, *(data++), MVTWSI_STATUS_DATA_W_ACK,
+				   tick);
 	/* Stop transaction */
-	stop_status = twsi_stop(twsi);
+	stop_status = twsi_stop(twsi, tick);
 	/* Return 0, or the status of the first failure */
 	return status != 0 ? status : stop_status;
 }
@@ -504,20 +534,21 @@ static void twsi_i2c_init(struct i2c_adapter *adap, int speed,
 			  int slaveadd)
 {
 	struct mvtwsi_registers *twsi = twsi_get_base(adap);
-	__twsi_i2c_init(twsi, speed, slaveadd);
+	__twsi_i2c_init(twsi, speed, slaveadd, NULL);
 }
 
 static uint twsi_i2c_set_bus_speed(struct i2c_adapter *adap,
 				   uint requested_speed)
 {
 	struct mvtwsi_registers *twsi = twsi_get_base(adap);
-	return __twsi_i2c_set_bus_speed(twsi, requested_speed);
+	__twsi_i2c_set_bus_speed(twsi, requested_speed);
+	return 0;
 }
 
 static int twsi_i2c_probe(struct i2c_adapter *adap, uchar chip)
 {
 	struct mvtwsi_registers *twsi = twsi_get_base(adap);
-	return __twsi_i2c_probe_chip(twsi, chip);
+	return __twsi_i2c_probe_chip(twsi, chip, 10000);
 }
 
 static int twsi_i2c_read(struct i2c_adapter *adap, uchar chip, uint addr,
@@ -531,7 +562,8 @@ static int twsi_i2c_read(struct i2c_adapter *adap, uchar chip, uint addr,
 	addr_bytes[2] = (addr >> 16) & 0xFF;
 	addr_bytes[3] = (addr >> 24) & 0xFF;
 
-	return __twsi_i2c_read(twsi, chip, addr_bytes, alen, data, length);
+	return __twsi_i2c_read(twsi, chip, addr_bytes, alen, data, length,
+			       10000);
 }
 
 static int twsi_i2c_write(struct i2c_adapter *adap, uchar chip, uint addr,
@@ -545,7 +577,8 @@ static int twsi_i2c_write(struct i2c_adapter *adap, uchar chip, uint addr,
 	addr_bytes[2] = (addr >> 16) & 0xFF;
 	addr_bytes[3] = (addr >> 24) & 0xFF;
 
-	return __twsi_i2c_write(twsi, chip, addr_bytes, alen, data, length);
+	return __twsi_i2c_write(twsi, chip, addr_bytes, alen, data, length,
+				10000);
 }
 
 #ifdef CONFIG_I2C_MVTWSI_BASE0
@@ -595,13 +628,17 @@ static int mvtwsi_i2c_probe_chip(struct udevice *bus, u32 chip_addr,
 				 u32 chip_flags)
 {
 	struct mvtwsi_i2c_dev *dev = dev_get_priv(bus);
-	return __twsi_i2c_probe_chip(dev->base, chip_addr);
+	return __twsi_i2c_probe_chip(dev->base, chip_addr, dev->tick);
 }
 
 static int mvtwsi_i2c_set_bus_speed(struct udevice *bus, uint speed)
 {
 	struct mvtwsi_i2c_dev *dev = dev_get_priv(bus);
-	return __twsi_i2c_set_bus_speed(dev->base, speed);
+
+	dev->speed = __twsi_i2c_set_bus_speed(dev->base, speed);
+	dev->tick = calc_tick(dev->speed);
+
+	return 0;
 }
 
 static int mvtwsi_i2c_ofdata_to_platdata(struct udevice *bus)
@@ -625,7 +662,11 @@ static int mvtwsi_i2c_ofdata_to_platdata(struct udevice *bus)
 static int mvtwsi_i2c_probe(struct udevice *bus)
 {
 	struct mvtwsi_i2c_dev *dev = dev_get_priv(bus);
-	__twsi_i2c_init(dev->base, dev->speed, dev->slaveadd);
+	uint actual_speed;
+
+	__twsi_i2c_init(dev->base, dev->speed, dev->slaveadd, &actual_speed);
+	dev->speed = actual_speed;
+	dev->tick = calc_tick(dev->speed);
 	return 0;
 }
 
@@ -648,10 +689,12 @@ static int mvtwsi_i2c_xfer(struct udevice *bus, struct i2c_msg *msg, int nmsgs)
 
 	if (dmsg->flags & I2C_M_RD)
 		return __twsi_i2c_read(dev->base, dmsg->addr, omsg->buf,
-				       omsg->len, dmsg->buf, dmsg->len);
+				       omsg->len, dmsg->buf, dmsg->len,
+				       dev->tick);
 	else
 		return __twsi_i2c_write(dev->base, dmsg->addr, omsg->buf,
-					omsg->len, dmsg->buf, dmsg->len);
+					omsg->len, dmsg->buf, dmsg->len,
+					dev->tick);
 }
 
 static const struct dm_i2c_ops mvtwsi_i2c_ops = {