i2c: i2c-cdns: Detect unsupported sequences for rev 1.0

Revision 1.0 of this IP has a couple of issues, such as not supporting
repeated start conditions for read transfers.

So scan through the list of i2c messages for these conditions
and report an error if they are attempted.

This has been fixed for revision 1.4 of the IP, so only report the error
when the IP can really not do it.

Signed-off-by: Moritz Fischer <moritz.fischer@ettus.com>
Cc: Heiko Schocher <hs@denx.de>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: u-boot@lists.denx.de

drivers/i2c/i2c-cdns.c

@@ -67,6 +67,7 @@ struct cdns_i2c_regs {
 
 #define CDNS_I2C_FIFO_DEPTH		16
 #define CDNS_I2C_TRANSFER_SIZE_MAX	255 /* Controller transfer limit */
+#define CDNS_I2C_BROKEN_HOLD_BIT	BIT(0)
 
 #ifdef DEBUG
 static void cdns_i2c_debug_status(struct cdns_i2c_regs *cdns_i2c)
@@ -114,6 +115,13 @@ struct i2c_cdns_bus {
 	int id;
 	unsigned int input_freq;
 	struct cdns_i2c_regs __iomem *regs;	/* register base */
+
+	int hold_flag;
+	u32 quirks;
+};
+
+struct cdns_i2c_platform_data {
+	u32 quirks;
 };
 
 /* Wait for an interrupt */
@@ -236,18 +244,14 @@ static int cdns_i2c_probe_chip(struct udevice *bus, uint chip_addr,
 }
 
 static int cdns_i2c_write_data(struct i2c_cdns_bus *i2c_bus, u32 addr, u8 *data,
-			       u32 len, bool next_is_read)
+			       u32 len)
 {
 	u8 *cur_data = data;
 
 	struct cdns_i2c_regs *regs = i2c_bus->regs;
 
-	setbits_le32(&regs->control, CDNS_I2C_CONTROL_CLR_FIFO |
-		CDNS_I2C_CONTROL_HOLD);
+	setbits_le32(&regs->control, CDNS_I2C_CONTROL_CLR_FIFO);
 
-	/* if next is a read, we need to clear HOLD, doesn't work */
-	if (next_is_read)
-		clrbits_le32(&regs->control, CDNS_I2C_CONTROL_HOLD);
 
 	clrbits_le32(&regs->control, CDNS_I2C_CONTROL_RW);
 
@@ -267,7 +271,9 @@ static int cdns_i2c_write_data(struct i2c_cdns_bus *i2c_bus, u32 addr, u8 *data,
 	}
 
 	/* All done... release the bus */
-	clrbits_le32(&regs->control, CDNS_I2C_CONTROL_HOLD);
+	if (!i2c_bus->hold_flag)
+		clrbits_le32(&regs->control, CDNS_I2C_CONTROL_HOLD);
+
 	/* Wait for the address and data to be sent */
 	if (!cdns_i2c_wait(regs, CDNS_I2C_INTERRUPT_COMP))
 		return -ETIMEDOUT;
@@ -285,7 +291,7 @@ static int cdns_i2c_read_data(struct i2c_cdns_bus *i2c_bus, u32 addr, u8 *data,
 	struct cdns_i2c_regs *regs = i2c_bus->regs;
 
 	/* Check the hardware can handle the requested bytes */
-	if ((len < 0) || (len > CDNS_I2C_TRANSFER_SIZE_MAX))
+	if ((len < 0))
 		return -EINVAL;
 
 	setbits_le32(&regs->control, CDNS_I2C_CONTROL_CLR_FIFO |
@@ -310,7 +316,8 @@ static int cdns_i2c_read_data(struct i2c_cdns_bus *i2c_bus, u32 addr, u8 *data,
 			*(cur_data++) = readl(&regs->data);
 	} while (readl(&regs->transfer_size) != 0);
 	/* All done... release the bus */
-	clrbits_le32(&regs->control, CDNS_I2C_CONTROL_HOLD);
+	if (!i2c_bus->hold_flag)
+		clrbits_le32(&regs->control, CDNS_I2C_CONTROL_HOLD);
 
 #ifdef DEBUG
 	cdns_i2c_debug_status(regs);
@@ -322,19 +329,41 @@ static int cdns_i2c_xfer(struct udevice *dev, struct i2c_msg *msg,
 			 int nmsgs)
 {
 	struct i2c_cdns_bus *i2c_bus = dev_get_priv(dev);
-	int ret;
+	int ret, count;
+	bool hold_quirk;
+
+	hold_quirk = !!(i2c_bus->quirks & CDNS_I2C_BROKEN_HOLD_BIT);
+
+	if (nmsgs > 1) {
+		/*
+		 * This controller does not give completion interrupt after a
+		 * master receive message if HOLD bit is set (repeated start),
+		 * resulting in SW timeout. Hence, if a receive message is
+		 * followed by any other message, an error is returned
+		 * indicating that this sequence is not supported.
+		 */
+		for (count = 0; (count < nmsgs - 1) && hold_quirk; count++) {
+			if (msg[count].flags & I2C_M_RD) {
+				printf("Can't do repeated start after a receive message\n");
+				return -EOPNOTSUPP;
+			}
+		}
+
+		i2c_bus->hold_flag = 1;
+		setbits_le32(&i2c_bus->regs->control, CDNS_I2C_CONTROL_HOLD);
+	} else {
+		i2c_bus->hold_flag = 0;
+	}
 
 	debug("i2c_xfer: %d messages\n", nmsgs);
 	for (; nmsgs > 0; nmsgs--, msg++) {
-		bool next_is_read = nmsgs > 1 && (msg[1].flags & I2C_M_RD);
-
 		debug("i2c_xfer: chip=0x%x, len=0x%x\n", msg->addr, msg->len);
 		if (msg->flags & I2C_M_RD) {
 			ret = cdns_i2c_read_data(i2c_bus, msg->addr, msg->buf,
 						 msg->len);
 		} else {
 			ret = cdns_i2c_write_data(i2c_bus, msg->addr, msg->buf,
-						  msg->len, next_is_read);
+						  msg->len);
 		}
 		if (ret) {
 			debug("i2c_write: error sending\n");
@@ -348,11 +377,16 @@ static int cdns_i2c_xfer(struct udevice *dev, struct i2c_msg *msg,
 static int cdns_i2c_ofdata_to_platdata(struct udevice *dev)
 {
 	struct i2c_cdns_bus *i2c_bus = dev_get_priv(dev);
+	struct cdns_i2c_platform_data *pdata =
+		(struct cdns_i2c_platform_data *)dev_get_driver_data(dev);
 
 	i2c_bus->regs = (struct cdns_i2c_regs *)dev_get_addr(dev);
 	if (!i2c_bus->regs)
 		return -ENOMEM;
 
+	if (pdata)
+		i2c_bus->quirks = pdata->quirks;
+
 	i2c_bus->input_freq = 100000000; /* TODO hardcode input freq for now */
 
 	return 0;
@@ -364,8 +398,12 @@ static const struct dm_i2c_ops cdns_i2c_ops = {
 	.set_bus_speed = cdns_i2c_set_bus_speed,
 };
 
+static const struct cdns_i2c_platform_data r1p10_i2c_def = {
+	.quirks = CDNS_I2C_BROKEN_HOLD_BIT,
+};
+
 static const struct udevice_id cdns_i2c_of_match[] = {
-	{ .compatible = "cdns,i2c-r1p10" },
+	{ .compatible = "cdns,i2c-r1p10", .data = (ulong)&r1p10_i2c_def },
 	{ .compatible = "cdns,i2c-r1p14" },
 	{ /* end of table */ }
 };