ARM: OMAP: I2C: New read, write and probe functions

New i2c_read, i2c_write and i2c_probe functions, tested on OMAP4
(4430/60/70), OMAP5 (5430) and AM335X (3359); should work on older
OMAPs and derivatives as well. The only anticipated exception would
be the OMAP2420, which shall require driver modification.
- Rewritten i2c_read to operate correctly with all types of chips
  (old function could not read consistent data from some I2C slaves).
- Optimised i2c_write.
- New i2c_probe, performs write access vs read. The old probe could
  hang the system under certain conditions (e.g. unconfigured pads).
- The read/write/probe functions try to identify unconfigured bus.
- Status functions now read irqstatus_raw as per TRM guidelines
  (except for OMAP243X and OMAP34XX).
- Driver now supports up to I2C5 (OMAP5).

Signed-off-by: Lubomir Popov <lpopov@mm-sol.com>
Tested-by: Heiko Schocher <hs@denx.de>

drivers/i2c/omap24xx_i2c.c

@@ -18,6 +18,20 @@
  *
  * Adapted for OMAP2420 I2C, r-woodruff2@ti.com
  *
+ * Copyright (c) 2013 Lubomir Popov <lpopov@mm-sol.com>, MM Solutions
+ * New i2c_read, i2c_write and i2c_probe functions, tested on OMAP4
+ * (4430/60/70), OMAP5 (5430) and AM335X (3359); should work on older
+ * OMAPs and derivatives as well. The only anticipated exception would
+ * be the OMAP2420, which shall require driver modification.
+ * - Rewritten i2c_read to operate correctly with all types of chips
+ *   (old function could not read consistent data from some I2C slaves).
+ * - Optimized i2c_write.
+ * - New i2c_probe, performs write access vs read. The old probe could
+ *   hang the system under certain conditions (e.g. unconfigured pads).
+ * - The read/write/probe functions try to identify unconfigured bus.
+ * - Status functions now read irqstatus_raw as per TRM guidelines
+ *   (except for OMAP243X and OMAP34XX).
+ * - Driver now supports up to I2C5 (OMAP5).
  */
 
 #include <common.h>
@@ -31,8 +45,11 @@ DECLARE_GLOBAL_DATA_PTR;
 
 #define I2C_TIMEOUT	1000
 
+/* Absolutely safe for status update at 100 kHz I2C: */
+#define I2C_WAIT	200
+
 static int wait_for_bb(void);
-static u16 wait_for_pin(void);
+static u16 wait_for_event(void);
 static void flush_fifo(void);
 
 /*
@@ -137,10 +154,14 @@ void i2c_init(int speed, int slaveadd)
 	/* own address */
 	writew(slaveadd, &i2c_base->oa);
 	writew(I2C_CON_EN, &i2c_base->con);
-
-	/* have to enable intrrupts or OMAP i2c module doesn't work */
+#if defined(CONFIG_OMAP243X) || defined(CONFIG_OMAP34XX)
+	/*
+	 * Have to enable interrupts for OMAP2/3, these IPs don't have
+	 * an 'irqstatus_raw' register and we shall have to poll 'stat'
+	 */
 	writew(I2C_IE_XRDY_IE | I2C_IE_RRDY_IE | I2C_IE_ARDY_IE |
-		I2C_IE_NACK_IE | I2C_IE_AL_IE, &i2c_base->ie);
+	       I2C_IE_NACK_IE | I2C_IE_AL_IE, &i2c_base->ie);
+#endif
 	udelay(1000);
 	flush_fifo();
 	writew(0xFFFF, &i2c_base->stat);
@@ -150,88 +171,6 @@ void i2c_init(int speed, int slaveadd)
 		bus_initialized[current_bus] = 1;
 }
 
-static int i2c_read_byte(u8 devaddr, u16 regoffset, u8 alen, u8 *value)
-{
-	int i2c_error = 0;
-	u16 status;
-	int i = 2 - alen;
-	u8 tmpbuf[2] = {(regoffset) >> 8, regoffset & 0xff};
-	u16 w;
-
-	/* wait until bus not busy */
-	if (wait_for_bb())
-		return 1;
-
-	/* one byte only */
-	writew(alen, &i2c_base->cnt);
-	/* set slave address */
-	writew(devaddr, &i2c_base->sa);
-	/* no stop bit needed here */
-	writew(I2C_CON_EN | I2C_CON_MST | I2C_CON_STT |
-	      I2C_CON_TRX, &i2c_base->con);
-
-	/* send register offset */
-	while (1) {
-		status = wait_for_pin();
-		if (status == 0 || status & I2C_STAT_NACK) {
-			i2c_error = 1;
-			goto read_exit;
-		}
-		if (status & I2C_STAT_XRDY) {
-			w = tmpbuf[i++];
-#if !(defined(CONFIG_OMAP243X) || defined(CONFIG_OMAP34XX) || \
-	defined(CONFIG_OMAP44XX) || defined(CONFIG_AM33XX) || \
-	defined(CONFIG_OMAP54XX))
-			w |= tmpbuf[i++] << 8;
-#endif
-			writew(w, &i2c_base->data);
-			writew(I2C_STAT_XRDY, &i2c_base->stat);
-		}
-		if (status & I2C_STAT_ARDY) {
-			writew(I2C_STAT_ARDY, &i2c_base->stat);
-			break;
-		}
-	}
-
-	/* set slave address */
-	writew(devaddr, &i2c_base->sa);
-	/* read one byte from slave */
-	writew(1, &i2c_base->cnt);
-	/* need stop bit here */
-	writew(I2C_CON_EN | I2C_CON_MST |
-		I2C_CON_STT | I2C_CON_STP,
-		&i2c_base->con);
-
-	/* receive data */
-	while (1) {
-		status = wait_for_pin();
-		if (status == 0 || status & I2C_STAT_NACK) {
-			i2c_error = 1;
-			goto read_exit;
-		}
-		if (status & I2C_STAT_RRDY) {
-#if defined(CONFIG_OMAP243X) || defined(CONFIG_OMAP34XX) || \
-	defined(CONFIG_OMAP44XX) || defined(CONFIG_AM33XX) || \
-	defined(CONFIG_OMAP54XX)
-			*value = readb(&i2c_base->data);
-#else
-			*value = readw(&i2c_base->data);
-#endif
-			writew(I2C_STAT_RRDY, &i2c_base->stat);
-		}
-		if (status & I2C_STAT_ARDY) {
-			writew(I2C_STAT_ARDY, &i2c_base->stat);
-			break;
-		}
-	}
-
-read_exit:
-	flush_fifo();
-	writew(0xFFFF, &i2c_base->stat);
-	writew(0, &i2c_base->cnt);
-	return i2c_error;
-}
-
 static void flush_fifo(void)
 {	u16 stat;
 
@@ -241,13 +180,7 @@ static void flush_fifo(void)
 	while (1) {
 		stat = readw(&i2c_base->stat);
 		if (stat == I2C_STAT_RRDY) {
-#if defined(CONFIG_OMAP243X) || defined(CONFIG_OMAP34XX) || \
-	defined(CONFIG_OMAP44XX) || defined(CONFIG_AM33XX) || \
-	defined(CONFIG_OMAP54XX)
 			readb(&i2c_base->data);
-#else
-			readw(&i2c_base->data);
-#endif
 			writew(I2C_STAT_RRDY, &i2c_base->stat);
 			udelay(1000);
 		} else
@@ -255,6 +188,10 @@ static void flush_fifo(void)
 	}
 }
 
+/*
+ * i2c_probe: Use write access. Allows to identify addresses that are
+ *            write-only (like the config register of dual-port EEPROMs)
+ */
 int i2c_probe(uchar chip)
 {
 	u16 status;
@@ -263,61 +200,81 @@ int i2c_probe(uchar chip)
 	if (chip == readw(&i2c_base->oa))
 		return res;
 
-	/* wait until bus not busy */
+	/* Wait until bus is free */
 	if (wait_for_bb())
 		return res;
 
-	/* try to read one byte */
-	writew(1, &i2c_base->cnt);
-	/* set slave address */
+	/* No data transfer, slave addr only */
+	writew(0, &i2c_base->cnt);
+	/* Set slave address */
 	writew(chip, &i2c_base->sa);
-	/* stop bit needed here */
-	writew (I2C_CON_EN | I2C_CON_MST | I2C_CON_STT | I2C_CON_STP, &i2c_base->con);
-
-	while (1) {
-		status = wait_for_pin();
-		if (status == 0 || status & I2C_STAT_AL) {
-			res = 1;
-			goto probe_exit;
-		}
-		if (status & I2C_STAT_NACK) {
-			res = 1;
-			writew(0xff, &i2c_base->stat);
-			writew (readw (&i2c_base->con) | I2C_CON_STP, &i2c_base->con);
-
-			if (wait_for_bb())
-				res = 1;
-
-			break;
-		}
-		if (status & I2C_STAT_ARDY) {
-			writew(I2C_STAT_ARDY, &i2c_base->stat);
-			break;
-		}
-		if (status & I2C_STAT_RRDY) {
-			res = 0;
-#if defined(CONFIG_OMAP243X) || defined(CONFIG_OMAP34XX) || \
-	defined(CONFIG_OMAP44XX) || defined(CONFIG_AM33XX) || \
-	defined(CONFIG_OMAP54XX)
-			readb(&i2c_base->data);
-#else
-			readw(&i2c_base->data);
-#endif
-			writew(I2C_STAT_RRDY, &i2c_base->stat);
-		}
+	/* Stop bit needed here */
+	writew(I2C_CON_EN | I2C_CON_MST | I2C_CON_STT | I2C_CON_TRX |
+	       I2C_CON_STP, &i2c_base->con);
+
+	status = wait_for_event();
+
+	if ((status & ~I2C_STAT_XRDY) == 0 || (status & I2C_STAT_AL)) {
+		/*
+		 * With current high-level command implementation, notifying
+		 * the user shall flood the console with 127 messages. If
+		 * silent exit is desired upon unconfigured bus, remove the
+		 * following 'if' section:
+		 */
+		if (status == I2C_STAT_XRDY)
+			printf("i2c_probe: pads on bus %d probably not configured (status=0x%x)\n",
+			       current_bus, status);
+
+		goto pr_exit;
 	}
 
-probe_exit:
+	/* Check for ACK (!NAK) */
+	if (!(status & I2C_STAT_NACK)) {
+		res = 0;			/* Device found */
+		udelay(I2C_WAIT);		/* Required by AM335X in SPL */
+		/* Abort transfer (force idle state) */
+		writew(I2C_CON_MST | I2C_CON_TRX, &i2c_base->con); /* Reset */
+		udelay(1000);
+		writew(I2C_CON_EN | I2C_CON_MST | I2C_CON_TRX |
+		       I2C_CON_STP, &i2c_base->con);		/* STP */
+	}
+pr_exit:
 	flush_fifo();
-	/* don't allow any more data in... we don't want it. */
-	writew(0, &i2c_base->cnt);
 	writew(0xFFFF, &i2c_base->stat);
+	writew(0, &i2c_base->cnt);
 	return res;
 }
 
+/*
+ * i2c_read: Function now uses a single I2C read transaction with bulk transfer
+ *           of the requested number of bytes (note that the 'i2c md' command
+ *           limits this to 16 bytes anyway). If CONFIG_I2C_REPEATED_START is
+ *           defined in the board config header, this transaction shall be with
+ *           Repeated Start (Sr) between the address and data phases; otherwise
+ *           Stop-Start (P-S) shall be used (some I2C chips do require a P-S).
+ *           The address (reg offset) may be 0, 1 or 2 bytes long.
+ *           Function now reads correctly from chips that return more than one
+ *           byte of data per addressed register (like TI temperature sensors),
+ *           or that do not need a register address at all (such as some clock
+ *           distributors).
+ */
 int i2c_read(uchar chip, uint addr, int alen, uchar *buffer, int len)
 {
-	int i;
+	int i2c_error = 0;
+	u16 status;
+
+	if (alen < 0) {
+		puts("I2C read: addr len < 0\n");
+		return 1;
+	}
+	if (len < 0) {
+		puts("I2C read: data len < 0\n");
+		return 1;
+	}
+	if (buffer == NULL) {
+		puts("I2C read: NULL pointer passed\n");
+		return 1;
+	}
 
 	if (alen > 2) {
 		printf("I2C read: addr len %d not supported\n", alen);
@@ -329,24 +286,122 @@ int i2c_read(uchar chip, uint addr, int alen, uchar *buffer, int len)
 		return 1;
 	}
 
-	for (i = 0; i < len; i++) {
-		if (i2c_read_byte(chip, addr + i, alen, &buffer[i])) {
-			puts("I2C read: I/O error\n");
-			i2c_init(CONFIG_SYS_I2C_SPEED, CONFIG_SYS_I2C_SLAVE);
-			return 1;
+	/* Wait until bus not busy */
+	if (wait_for_bb())
+		return 1;
+
+	/* Zero, one or two bytes reg address (offset) */
+	writew(alen, &i2c_base->cnt);
+	/* Set slave address */
+	writew(chip, &i2c_base->sa);
+
+	if (alen) {
+		/* Must write reg offset first */
+#ifdef CONFIG_I2C_REPEATED_START
+		/* No stop bit, use Repeated Start (Sr) */
+		writew(I2C_CON_EN | I2C_CON_MST | I2C_CON_STT |
+		       I2C_CON_TRX, &i2c_base->con);
+#else
+		/* Stop - Start (P-S) */
+		writew(I2C_CON_EN | I2C_CON_MST | I2C_CON_STT | I2C_CON_STP |
+		       I2C_CON_TRX, &i2c_base->con);
+#endif
+		/* Send register offset */
+		while (1) {
+			status = wait_for_event();
+			/* Try to identify bus that is not padconf'd for I2C */
+			if (status == I2C_STAT_XRDY) {
+				i2c_error = 2;
+				printf("i2c_read (addr phase): pads on bus %d probably not configured (status=0x%x)\n",
+				       current_bus, status);
+				goto rd_exit;
+			}
+			if (status == 0 || status & I2C_STAT_NACK) {
+				i2c_error = 1;
+				printf("i2c_read: error waiting for addr ACK (status=0x%x)\n",
+				       status);
+				goto rd_exit;
+			}
+			if (alen) {
+				if (status & I2C_STAT_XRDY) {
+					alen--;
+					/* Do we have to use byte access? */
+					writeb((addr >> (8 * alen)) & 0xff,
+					       &i2c_base->data);
+					writew(I2C_STAT_XRDY, &i2c_base->stat);
+				}
+			}
+			if (status & I2C_STAT_ARDY) {
+				writew(I2C_STAT_ARDY, &i2c_base->stat);
+				break;
+			}
 		}
 	}
+	/* Set slave address */
+	writew(chip, &i2c_base->sa);
+	/* Read len bytes from slave */
+	writew(len, &i2c_base->cnt);
+	/* Need stop bit here */
+	writew(I2C_CON_EN | I2C_CON_MST |
+	       I2C_CON_STT | I2C_CON_STP,
+	       &i2c_base->con);
 
-	return 0;
+	/* Receive data */
+	while (1) {
+		status = wait_for_event();
+		/*
+		 * Try to identify bus that is not padconf'd for I2C. This
+		 * state could be left over from previous transactions if
+		 * the address phase is skipped due to alen=0.
+		 */
+		if (status == I2C_STAT_XRDY) {
+			i2c_error = 2;
+			printf("i2c_read (data phase): pads on bus %d probably not configured (status=0x%x)\n",
+			       current_bus, status);
+			goto rd_exit;
+		}
+		if (status == 0 || status & I2C_STAT_NACK) {
+			i2c_error = 1;
+			goto rd_exit;
+		}
+		if (status & I2C_STAT_RRDY) {
+			*buffer++ = readb(&i2c_base->data);
+			writew(I2C_STAT_RRDY, &i2c_base->stat);
+		}
+		if (status & I2C_STAT_ARDY) {
+			writew(I2C_STAT_ARDY, &i2c_base->stat);
+			break;
+		}
+	}
+
+rd_exit:
+	flush_fifo();
+	writew(0xFFFF, &i2c_base->stat);
+	writew(0, &i2c_base->cnt);
+	return i2c_error;
 }
 
+/* i2c_write: Address (reg offset) may be 0, 1 or 2 bytes long. */
 int i2c_write(uchar chip, uint addr, int alen, uchar *buffer, int len)
 {
 	int i;
 	u16 status;
 	int i2c_error = 0;
-	u16 w;
-	u8 tmpbuf[2] = {addr >> 8, addr & 0xff};
+
+	if (alen < 0) {
+		puts("I2C write: addr len < 0\n");
+		return 1;
+	}
+
+	if (len < 0) {
+		puts("I2C write: data len < 0\n");
+		return 1;
+	}
+
+	if (buffer == NULL) {
+		puts("I2C write: NULL pointer passed\n");
+		return 1;
+	}
 
 	if (alen > 2) {
 		printf("I2C write: addr len %d not supported\n", alen);
@@ -355,92 +410,137 @@ int i2c_write(uchar chip, uint addr, int alen, uchar *buffer, int len)
 
 	if (addr + len > (1 << 16)) {
 		printf("I2C write: address 0x%x + 0x%x out of range\n",
-				addr, len);
+		       addr, len);
 		return 1;
 	}
 
-	/* wait until bus not busy */
+	/* Wait until bus not busy */
 	if (wait_for_bb())
 		return 1;
 
-	/* start address phase - will write regoffset + len bytes data */
-	/* TODO consider case when !CONFIG_OMAP243X/34XX/44XX */
+	/* Start address phase - will write regoffset + len bytes data */
 	writew(alen + len, &i2c_base->cnt);
-	/* set slave address */
+	/* Set slave address */
 	writew(chip, &i2c_base->sa);
-	/* stop bit needed here */
+	/* Stop bit needed here */
 	writew(I2C_CON_EN | I2C_CON_MST | I2C_CON_STT | I2C_CON_TRX |
-		I2C_CON_STP, &i2c_base->con);
-
-	/* Send address and data */
-	for (i = -alen; i < len; i++) {
-		status = wait_for_pin();
-
+	       I2C_CON_STP, &i2c_base->con);
+
+	while (alen) {
+		/* Must write reg offset (one or two bytes) */
+		status = wait_for_event();
+		/* Try to identify bus that is not padconf'd for I2C */
+		if (status == I2C_STAT_XRDY) {
+			i2c_error = 2;
+			printf("i2c_write: pads on bus %d probably not configured (status=0x%x)\n",
+			       current_bus, status);
+			goto wr_exit;
+		}
 		if (status == 0 || status & I2C_STAT_NACK) {
 			i2c_error = 1;
-			printf("i2c error waiting for data ACK (status=0x%x)\n",
-					status);
-			goto write_exit;
+			printf("i2c_write: error waiting for addr ACK (status=0x%x)\n",
+			       status);
+			goto wr_exit;
 		}
-
 		if (status & I2C_STAT_XRDY) {
-			w = (i < 0) ? tmpbuf[2+i] : buffer[i];
-#if !(defined(CONFIG_OMAP243X) || defined(CONFIG_OMAP34XX) || \
-	defined(CONFIG_OMAP44XX) || defined(CONFIG_AM33XX) || \
-	defined(CONFIG_OMAP54XX))
-			w |= ((++i < 0) ? tmpbuf[2+i] : buffer[i]) << 8;
-#endif
-			writew(w, &i2c_base->data);
+			alen--;
+			writeb((addr >> (8 * alen)) & 0xff, &i2c_base->data);
+			writew(I2C_STAT_XRDY, &i2c_base->stat);
+		} else {
+			i2c_error = 1;
+			printf("i2c_write: bus not ready for addr Tx (status=0x%x)\n",
+			       status);
+			goto wr_exit;
+		}
+	}
+	/* Address phase is over, now write data */
+	for (i = 0; i < len; i++) {
+		status = wait_for_event();
+		if (status == 0 || status & I2C_STAT_NACK) {
+			i2c_error = 1;
+			printf("i2c_write: error waiting for data ACK (status=0x%x)\n",
+			       status);
+			goto wr_exit;
+		}
+		if (status & I2C_STAT_XRDY) {
+			writeb(buffer[i], &i2c_base->data);
 			writew(I2C_STAT_XRDY, &i2c_base->stat);
 		} else {
 			i2c_error = 1;
-			printf("i2c bus not ready for Tx (i=%d)\n", i);
-			goto write_exit;
+			printf("i2c_write: bus not ready for data Tx (i=%d)\n",
+			       i);
+			goto wr_exit;
 		}
 	}
 
-write_exit:
+wr_exit:
 	flush_fifo();
 	writew(0xFFFF, &i2c_base->stat);
+	writew(0, &i2c_base->cnt);
 	return i2c_error;
 }
 
+/*
+ * Wait for the bus to be free by checking the Bus Busy (BB)
+ * bit to become clear
+ */
 static int wait_for_bb(void)
 {
 	int timeout = I2C_TIMEOUT;
 	u16 stat;
 
 	writew(0xFFFF, &i2c_base->stat);	/* clear current interrupts...*/
+#if defined(CONFIG_OMAP243X) || defined(CONFIG_OMAP34XX)
 	while ((stat = readw(&i2c_base->stat) & I2C_STAT_BB) && timeout--) {
+#else
+	/* Read RAW status */
+	while ((stat = readw(&i2c_base->irqstatus_raw) &
+		I2C_STAT_BB) && timeout--) {
+#endif
 		writew(stat, &i2c_base->stat);
-		udelay(1000);
+		udelay(I2C_WAIT);
 	}
 
 	if (timeout <= 0) {
-		printf("timed out in wait_for_bb: I2C_STAT=%x\n",
-			readw(&i2c_base->stat));
+		printf("Timed out in wait_for_bb: status=%04x\n",
+		       stat);
 		return 1;
 	}
 	writew(0xFFFF, &i2c_base->stat);	 /* clear delayed stuff*/
 	return 0;
 }
 
-static u16 wait_for_pin(void)
+/*
+ * Wait for the I2C controller to complete current action
+ * and update status
+ */
+static u16 wait_for_event(void)
 {
 	u16 status;
 	int timeout = I2C_TIMEOUT;
 
 	do {
-		udelay(1000);
+		udelay(I2C_WAIT);
+#if defined(CONFIG_OMAP243X) || defined(CONFIG_OMAP34XX)
 		status = readw(&i2c_base->stat);
+#else
+		/* Read RAW status */
+		status = readw(&i2c_base->irqstatus_raw);
+#endif
 	} while (!(status &
 		   (I2C_STAT_ROVR | I2C_STAT_XUDF | I2C_STAT_XRDY |
 		    I2C_STAT_RRDY | I2C_STAT_ARDY | I2C_STAT_NACK |
 		    I2C_STAT_AL)) && timeout--);
 
 	if (timeout <= 0) {
-		printf("timed out in wait_for_pin: I2C_STAT=%x\n",
-			readw(&i2c_base->stat));
+		printf("Timed out in wait_for_event: status=%04x\n",
+		       status);
+		/*
+		 * If status is still 0 here, probably the bus pads have
+		 * not been configured for I2C, and/or pull-ups are missing.
+		 */
+		printf("Check if pads/pull-ups of bus %d are properly configured\n",
+		       current_bus);
 		writew(0xFFFF, &i2c_base->stat);
 		status = 0;
 	}
@@ -450,28 +550,36 @@ static u16 wait_for_pin(void)
 
 int i2c_set_bus_num(unsigned int bus)
 {
-	if ((bus < 0) || (bus >= I2C_BUS_MAX)) {
-		printf("Bad bus: %d\n", bus);
+	if (bus >= I2C_BUS_MAX) {
+		printf("Bad bus: %x\n", bus);
 		return -1;
 	}
 
-#if I2C_BUS_MAX == 4
-	if (bus == 3)
-		i2c_base = (struct i2c *)I2C_BASE4;
-	else
-	if (bus == 2)
+	switch (bus) {
+	default:
+		bus = 0;	/* Fall through */
+	case 0:
+		i2c_base = (struct i2c *)I2C_BASE1;
+		break;
+	case 1:
+		i2c_base = (struct i2c *)I2C_BASE2;
+		break;
+#if (I2C_BUS_MAX > 2)
+	case 2:
 		i2c_base = (struct i2c *)I2C_BASE3;
-	else
+		break;
+#if (I2C_BUS_MAX > 3)
+	case 3:
+		i2c_base = (struct i2c *)I2C_BASE4;
+		break;
+#if (I2C_BUS_MAX > 4)
+	case 4:
+		i2c_base = (struct i2c *)I2C_BASE5;
+		break;
 #endif
-#if I2C_BUS_MAX == 3
-	if (bus == 2)
-		i2c_base = (struct i2c *)I2C_BASE3;
-	else
 #endif
-	if (bus == 1)
-		i2c_base = (struct i2c *)I2C_BASE2;
-	else
-		i2c_base = (struct i2c *)I2C_BASE1;
+#endif
+	}
 
 	current_bus = bus;