Subject: [PATCH V6 3/6] i2c: qup: Transfer each i2c_msg in i2c_msgs without a stop bit

From: [email-masked] (Sricharan R)
Date: Tue, 12 Jan 2016 14:13:50 +0530

The definition of i2c_msg says that

"If this is the last message in a group, it is followed by a STOP.
Otherwise it is followed by the next @i2c_msg transaction segment,
beginning with a (repeated) START"

So the expectation is that there is no 'STOP' bit inbetween individual
i2c_msg segments with repeated 'START'. The QUP i2c hardware has no way
to inform that there should not be a 'STOP' at the end of transaction.
The only way to implement this is to coalesce all the i2c_msg in i2c_msgs
in to one transaction and transfer them. Adding the support for the same.

This is required for some clients like touchscreen which keeps
incrementing counts across individual transfers and 'STOP' bit inbetween
resets the counter, which is not required.

This patch adds the support in non-dma mode.

Signed-off-by: Sricharan R <[email-masked]>
Reviewed-by: Andy Gross <[email-masked]>
---
 drivers/i2c/busses/i2c-qup.c | 34 ++++++++++++++++++++++++++--------
 1 file changed, 26 insertions(+), 8 deletions(-)

diff --git a/drivers/i2c/busses/i2c-qup.c b/drivers/i2c/busses/i2c-qup.c
index 715d4d7..f9009d6 100644
--- a/drivers/i2c/busses/i2c-qup.c
+++ b/drivers/i2c/busses/i2c-qup.c
@@ -112,6 +112,7 @@
 #define SET_BIT				0x1
 #define RESET_BIT			0x0
 #define ONE_BYTE			0x1
+#define QUP_I2C_MX_CONFIG_DURING_RUN   BIT(31)
 
 struct qup_i2c_block {
 	int	count;
@@ -147,6 +148,12 @@ struct qup_i2c_dev {
 	/* QUP core errors */
 	u32			qup_err;
 
+	/* To check if this is the last msg */
+	bool			is_last;
+
+	/* To configure when bus is in run state */
+	int			config_run;
+
 	struct completion	xfer;
 };
 
@@ -269,7 +276,7 @@ static int qup_i2c_wait_ready(struct qup_i2c_dev *qup, int op, bool val,
 		status = readl(qup->base + QUP_I2C_STATUS);
 
 		if (((opflags & op) >> shift) == val) {
-			if (op == QUP_OUT_NOT_EMPTY) {
+			if ((op == QUP_OUT_NOT_EMPTY) && qup->is_last) {
 				if (!(status & I2C_STATUS_BUS_ACTIVE))
 					return 0;
 			} else {
@@ -290,6 +297,8 @@ static void qup_i2c_set_write_mode_v2(struct qup_i2c_dev *qup,
 	/* Number of entries to shift out, including the tags */
 	int total = msg->len + qup->blk.tx_tag_len;
 
+	total |= qup->config_run;
+
 	if (total < qup->out_fifo_sz) {
 		/* FIFO mode */
 		writel(QUP_REPACK_EN, qup->base + QUP_IO_MODE);
@@ -443,7 +452,7 @@ static int qup_i2c_set_tags(u8 *tags, struct qup_i2c_dev *qup,
 	}
 
 	/* Send _STOP commands for the last block */
-	if (qup->blk.pos == (qup->blk.count - 1)) {
+	if ((qup->blk.pos == (qup->blk.count - 1)) && qup->is_last) {
 		if (msg->flags & I2C_M_RD)
 			tags[len++] = QUP_TAG_V2_DATARD_STOP;
 		else
@@ -581,7 +590,6 @@ static int qup_i2c_write_one(struct qup_i2c_dev *qup, struct i2c_msg *msg)
 
 	/* Wait for the outstanding data in the fifo to drain */
 	ret = qup_i2c_wait_ready(qup, QUP_OUT_NOT_EMPTY, RESET_BIT, ONE_BYTE);
-
 err:
 	disable_irq(qup->irq);
 	qup->msg = NULL;
@@ -608,18 +616,20 @@ static void qup_i2c_set_read_mode_v2(struct qup_i2c_dev *qup, int len)
 	int tx_len = qup->blk.tx_tag_len;
 
 	len += qup->blk.rx_tag_len;
+	len |= qup->config_run;
+	tx_len |= qup->config_run;
 
 	if (len < qup->in_fifo_sz) {
 		/* FIFO mode */
 		writel(QUP_REPACK_EN, qup->base + QUP_IO_MODE);
-		writel(len, qup->base + QUP_MX_READ_CNT);
 		writel(tx_len, qup->base + QUP_MX_WRITE_CNT);
+		writel(len, qup->base + QUP_MX_READ_CNT);
 	} else {
 		/* BLOCK mode (transfer data on chunks) */
 		writel(QUP_INPUT_BLK_MODE | QUP_REPACK_EN,
 		       qup->base + QUP_IO_MODE);
-		writel(len, qup->base + QUP_MX_INPUT_CNT);
 		writel(tx_len, qup->base + QUP_MX_OUTPUT_CNT);
+		writel(len, qup->base + QUP_MX_INPUT_CNT);
 	}
 }
 
@@ -866,6 +876,12 @@ static int qup_i2c_xfer_v2(struct i2c_adapter *adap,
 			goto out;
 		}
 
+		qup->is_last = (idx == (num - 1));
+		if (idx)
+			qup->config_run = QUP_I2C_MX_CONFIG_DURING_RUN;
+		else
+			qup->config_run = 0;
+
 		reinit_completion(&qup->xfer);
 
 		if (msgs[idx].flags & I2C_M_RD)
@@ -873,13 +889,13 @@ static int qup_i2c_xfer_v2(struct i2c_adapter *adap,
 		else
 			ret = qup_i2c_write_one_v2(qup, &msgs[idx]);
 
-		if (!ret)
-			ret = qup_i2c_change_state(qup, QUP_RESET_STATE);
-
 		if (ret)
 			break;
 	}
 
+	if (!ret)
+		ret = qup_i2c_change_state(qup, QUP_RESET_STATE);
+
 	if (ret == 0)
 		ret = num;
 out:
@@ -1057,6 +1073,8 @@ static int qup_i2c_probe(struct platform_device *pdev)
 	i2c_set_adapdata(&qup->adap, qup);
 	qup->adap.dev.parent = qup->dev;
 	qup->adap.dev.of_node = pdev->dev.of_node;
+	qup->is_last = 1;
+
 	strlcpy(qup->adap.name, "QUP I2C adapter", sizeof(qup->adap.name));
 
 	pm_runtime_set_autosuspend_delay(qup->dev, MSEC_PER_SEC);
-- 
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