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From:   Abhishek Sahu <absahu@codeaurora.org>
To:     Andy Gross <andy.gross@linaro.org>,
        Wolfram Sang <wsa@the-dreams.de>
Cc:     David Brown <david.brown@linaro.org>,
        Sricharan R <sricharan@codeaurora.org>,
        Austin Christ <austinwc@codeaurora.org>,
        linux-arm-msm@vger.kernel.org, linux-soc@vger.kernel.org,
        linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org,
        Abhishek Sahu <absahu@codeaurora.org>
Subject: [PATCH v2 12/13] i2c: qup: reorganization of driver code to remove polling for qup v1
Date:   Mon, 12 Mar 2018 18:45:01 +0530
Message-Id: <1520860502-14886-13-git-send-email-absahu@codeaurora.org>
In-Reply-To: <1520860502-14886-1-git-send-email-absahu@codeaurora.org>
References: <1520860502-14886-1-git-send-email-absahu@codeaurora.org>
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Following are the major issues in current driver code

1. The current driver simply assumes the transfer completion
   whenever its gets any non-error interrupts and then simply do the
   polling of available/free bytes in FIFO.
2. The block mode is not working properly since no handling in
   being done for OUT_BLOCK_WRITE_REQ and IN_BLOCK_READ_REQ.

Because of above, i2c v1 transfers of size greater than 32 are failing
with following error message

	i2c_qup 78b6000.i2c: timeout for fifo out full

To make block mode working properly and move to use the interrupts
instead of polling, major code reorganization is required. Following
are the major changes done in this patch

1. Remove the polling of TX FIFO free space and RX FIFO available
   bytes and move to interrupts completely. QUP has QUP_MX_OUTPUT_DONE,
   QUP_MX_INPUT_DONE, OUT_BLOCK_WRITE_REQ and IN_BLOCK_READ_REQ
   interrupts to handle FIFO’s properly so check all these interrupts.
2. During write, For FIFO mode, TX FIFO can be directly written
   without checking for FIFO space. For block mode, the QUP will generate
   OUT_BLOCK_WRITE_REQ interrupt whenever it has block size of available
   space.
3. During read, both TX and RX FIFO will be used. TX will be used
   for writing tags and RX will be used for receiving the data. In QUP,
   TX and RX can operate in separate mode so configure modes accordingly.
4. For read FIFO mode, wait for QUP_MX_INPUT_DONE interrupt which
   will be generated after all the bytes have been copied in RX FIFO. For
   read Block mode, QUP will generate IN_BLOCK_READ_REQ interrupts
   whenever it has block size of available data.

Signed-off-by: Abhishek Sahu <absahu@codeaurora.org>
---

* Changes from v1:

1. Fixed auto build test WARNING ‘idx' may be used uninitialized
   in this function
2. Removed event-based completion and changed transfer completion
   detection logic in interrupt handler

 drivers/i2c/busses/i2c-qup.c | 368 ++++++++++++++++++++++++++-----------------
 1 file changed, 224 insertions(+), 144 deletions(-)

diff --git a/drivers/i2c/busses/i2c-qup.c b/drivers/i2c/busses/i2c-qup.c
index 4ebd922..3bf3c34 100644
--- a/drivers/i2c/busses/i2c-qup.c
+++ b/drivers/i2c/busses/i2c-qup.c
@@ -64,8 +64,11 @@
 #define QUP_IN_SVC_FLAG		BIT(9)
 #define QUP_MX_OUTPUT_DONE	BIT(10)
 #define QUP_MX_INPUT_DONE	BIT(11)
+#define OUT_BLOCK_WRITE_REQ	BIT(12)
+#define IN_BLOCK_READ_REQ	BIT(13)
 
 /* I2C mini core related values */
+#define QUP_NO_INPUT		BIT(7)
 #define QUP_CLOCK_AUTO_GATE	BIT(13)
 #define I2C_MINI_CORE		(2 << 8)
 #define I2C_N_VAL		15
@@ -137,13 +140,36 @@
 #define DEFAULT_CLK_FREQ 100000
 #define DEFAULT_SRC_CLK 20000000
 
+/*
+ * count: no of blocks
+ * pos: current block number
+ * tx_tag_len: tx tag length for current block
+ * rx_tag_len: rx tag length for current block
+ * data_len: remaining data length for current message
+ * total_tx_len: total tx length including tag bytes for current QUP transfer
+ * total_rx_len: total rx length including tag bytes for current QUP transfer
+ * tx_fifo_free: number of free bytes in current QUP block write.
+ * fifo_available: number of available bytes in RX FIFO for current
+ *		   QUP block read
+ * rx_bytes_read: if all the bytes have been read from rx FIFO.
+ * is_tx_blk_mode: whether tx uses block or FIFO mode in case of non BAM xfer.
+ * is_rx_blk_mode: whether rx uses block or FIFO mode in case of non BAM xfer.
+ * tags: contains tx tag bytes for current QUP transfer
+ */
 struct qup_i2c_block {
-	int	count;
-	int	pos;
-	int	tx_tag_len;
-	int	rx_tag_len;
-	int	data_len;
-	u8	tags[6];
+	int		count;
+	int		pos;
+	int		tx_tag_len;
+	int		rx_tag_len;
+	int		data_len;
+	int		total_tx_len;
+	int		total_rx_len;
+	int		tx_fifo_free;
+	int		fifo_available;
+	bool		rx_bytes_read;
+	bool		is_tx_blk_mode;
+	bool		is_rx_blk_mode;
+	u8		tags[6];
 };
 
 struct qup_i2c_tag {
@@ -186,6 +212,7 @@ struct qup_i2c_dev {
 
 	/* To check if this is the last msg */
 	bool			is_last;
+	bool			is_qup_v1;
 
 	/* To configure when bus is in run state */
 	int			config_run;
@@ -202,11 +229,18 @@ struct qup_i2c_dev {
 	struct			qup_i2c_bam btx;
 
 	struct completion	xfer;
+	/* function to write data in tx fifo */
+	void (*write_tx_fifo)(struct qup_i2c_dev *qup);
+	/* function to read data from rx fifo */
+	void (*read_rx_fifo)(struct qup_i2c_dev *qup);
+	/* function to write tags in tx fifo for i2c read transfer */
+	void (*write_rx_tags)(struct qup_i2c_dev *qup);
 };
 
 static irqreturn_t qup_i2c_interrupt(int irq, void *dev)
 {
 	struct qup_i2c_dev *qup = dev;
+	struct qup_i2c_block *blk = &qup->blk;
 	u32 bus_err;
 	u32 qup_err;
 	u32 opflags;
@@ -253,12 +287,48 @@ static irqreturn_t qup_i2c_interrupt(int irq, void *dev)
 		goto done;
 	}
 
-	if (opflags & QUP_IN_SVC_FLAG)
-		writel(QUP_IN_SVC_FLAG, qup->base + QUP_OPERATIONAL);
+	if (!qup->is_qup_v1)
+		goto done;
 
-	if (opflags & QUP_OUT_SVC_FLAG)
+	if (opflags & QUP_OUT_SVC_FLAG) {
 		writel(QUP_OUT_SVC_FLAG, qup->base + QUP_OPERATIONAL);
 
+		if (opflags & OUT_BLOCK_WRITE_REQ) {
+			blk->tx_fifo_free += qup->out_blk_sz;
+			if (qup->msg->flags & I2C_M_RD)
+				qup->write_rx_tags(qup);
+			else
+				qup->write_tx_fifo(qup);
+		}
+	}
+
+	if (opflags & QUP_IN_SVC_FLAG) {
+		writel(QUP_IN_SVC_FLAG, qup->base + QUP_OPERATIONAL);
+
+		if (!blk->is_rx_blk_mode) {
+			blk->fifo_available += qup->in_fifo_sz;
+			qup->read_rx_fifo(qup);
+		} else if (opflags & IN_BLOCK_READ_REQ) {
+			blk->fifo_available += qup->in_blk_sz;
+			qup->read_rx_fifo(qup);
+		}
+	}
+
+	if (qup->msg->flags & I2C_M_RD) {
+		if (!blk->rx_bytes_read)
+			return IRQ_HANDLED;
+	} else {
+		/*
+		 * Ideally, QUP_MAX_OUTPUT_DONE_FLAG should be checked
+		 * for FIFO mode also. But, QUP_MAX_OUTPUT_DONE_FLAG lags
+		 * behind QUP_OUTPUT_SERVICE_FLAG sometimes. The only reason
+		 * of interrupt for write message in FIFO mode is
+		 * QUP_MAX_OUTPUT_DONE_FLAG condition.
+		 */
+		if (blk->is_tx_blk_mode && !(opflags & QUP_MX_OUTPUT_DONE))
+			return IRQ_HANDLED;
+	}
+
 done:
 	qup->qup_err = qup_err;
 	qup->bus_err = bus_err;
@@ -324,6 +394,28 @@ static int qup_i2c_change_state(struct qup_i2c_dev *qup, u32 state)
 	return 0;
 }
 
+/* Check if I2C bus returns to IDLE state */
+static int qup_i2c_bus_active(struct qup_i2c_dev *qup, int len)
+{
+	unsigned long timeout;
+	u32 status;
+	int ret = 0;
+
+	timeout = jiffies + len * 4;
+	for (;;) {
+		status = readl(qup->base + QUP_I2C_STATUS);
+		if (!(status & I2C_STATUS_BUS_ACTIVE))
+			break;
+
+		if (time_after(jiffies, timeout))
+			ret = -ETIMEDOUT;
+
+		usleep_range(len, len * 2);
+	}
+
+	return ret;
+}
+
 /**
  * qup_i2c_wait_ready - wait for a give number of bytes in tx/rx path
  * @qup: The qup_i2c_dev device
@@ -394,23 +486,6 @@ static void qup_i2c_set_write_mode_v2(struct qup_i2c_dev *qup,
 	}
 }
 
-static void qup_i2c_set_write_mode(struct qup_i2c_dev *qup, struct i2c_msg *msg)
-{
-	/* Number of entries to shift out, including the start */
-	int total = msg->len + 1;
-
-	if (total < qup->out_fifo_sz) {
-		/* FIFO mode */
-		writel(QUP_REPACK_EN, qup->base + QUP_IO_MODE);
-		writel(total, qup->base + QUP_MX_WRITE_CNT);
-	} else {
-		/* BLOCK mode (transfer data on chunks) */
-		writel(QUP_OUTPUT_BLK_MODE | QUP_REPACK_EN,
-		       qup->base + QUP_IO_MODE);
-		writel(total, qup->base + QUP_MX_OUTPUT_CNT);
-	}
-}
-
 static int check_for_fifo_space(struct qup_i2c_dev *qup)
 {
 	int ret;
@@ -443,28 +518,25 @@ static int check_for_fifo_space(struct qup_i2c_dev *qup)
 	return ret;
 }
 
-static int qup_i2c_issue_write(struct qup_i2c_dev *qup, struct i2c_msg *msg)
+static void qup_i2c_write_tx_fifo_v1(struct qup_i2c_dev *qup)
 {
+	struct qup_i2c_block *blk = &qup->blk;
+	struct i2c_msg *msg = qup->msg;
 	u32 addr = msg->addr << 1;
 	u32 qup_tag;
 	int idx;
 	u32 val;
-	int ret = 0;
 
 	if (qup->pos == 0) {
 		val = QUP_TAG_START | addr;
 		idx = 1;
+		blk->tx_fifo_free--;
 	} else {
 		val = 0;
 		idx = 0;
 	}
 
-	while (qup->pos < msg->len) {
-		/* Check that there's space in the FIFO for our pair */
-		ret = check_for_fifo_space(qup);
-		if (ret)
-			return ret;
-
+	while (blk->tx_fifo_free && qup->pos < msg->len) {
 		if (qup->pos == msg->len - 1)
 			qup_tag = QUP_TAG_STOP;
 		else
@@ -481,11 +553,8 @@ static int qup_i2c_issue_write(struct qup_i2c_dev *qup, struct i2c_msg *msg)
 
 		qup->pos++;
 		idx++;
+		blk->tx_fifo_free--;
 	}
-
-	ret = qup_i2c_change_state(qup, QUP_RUN_STATE);
-
-	return ret;
 }
 
 static void qup_i2c_set_blk_data(struct qup_i2c_dev *qup,
@@ -1006,64 +1075,6 @@ static int qup_i2c_write_one_v2(struct qup_i2c_dev *qup, struct i2c_msg *msg)
 	return ret;
 }
 
-static int qup_i2c_write_one(struct qup_i2c_dev *qup, struct i2c_msg *msg)
-{
-	int ret;
-
-	qup->msg = msg;
-	qup->pos = 0;
-
-	enable_irq(qup->irq);
-
-	qup_i2c_set_write_mode(qup, msg);
-
-	ret = qup_i2c_change_state(qup, QUP_RUN_STATE);
-	if (ret)
-		goto err;
-
-	writel(qup->clk_ctl, qup->base + QUP_I2C_CLK_CTL);
-
-	do {
-		ret = qup_i2c_change_state(qup, QUP_PAUSE_STATE);
-		if (ret)
-			goto err;
-
-		ret = qup_i2c_issue_write(qup, msg);
-		if (ret)
-			goto err;
-
-		ret = qup_i2c_change_state(qup, QUP_RUN_STATE);
-		if (ret)
-			goto err;
-
-		ret = qup_i2c_wait_for_complete(qup, msg);
-		if (ret)
-			goto err;
-	} while (qup->pos < msg->len);
-
-	/* 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;
-
-	return ret;
-}
-
-static void qup_i2c_set_read_mode(struct qup_i2c_dev *qup, int len)
-{
-	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);
-	} 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);
-	}
-}
-
 static void qup_i2c_set_read_mode_v2(struct qup_i2c_dev *qup, int len)
 {
 	int tx_len = qup->blk.tx_tag_len;
@@ -1086,44 +1097,27 @@ static void qup_i2c_set_read_mode_v2(struct qup_i2c_dev *qup, int len)
 	}
 }
 
-static void qup_i2c_issue_read(struct qup_i2c_dev *qup, struct i2c_msg *msg)
-{
-	u32 addr, len, val;
-
-	addr = i2c_8bit_addr_from_msg(msg);
-
-	/* 0 is used to specify a length 256 (QUP_READ_LIMIT) */
-	len = (msg->len == QUP_READ_LIMIT) ? 0 : msg->len;
-
-	val = ((QUP_TAG_REC | len) << QUP_MSW_SHIFT) | QUP_TAG_START | addr;
-	writel(val, qup->base + QUP_OUT_FIFO_BASE);
-}
-
-
-static int qup_i2c_read_fifo(struct qup_i2c_dev *qup, struct i2c_msg *msg)
+static void qup_i2c_read_rx_fifo_v1(struct qup_i2c_dev *qup)
 {
+	struct qup_i2c_block *blk = &qup->blk;
+	struct i2c_msg *msg = qup->msg;
 	u32 val = 0;
-	int idx;
-	int ret = 0;
+	int idx = 0;
 
-	for (idx = 0; qup->pos < msg->len; idx++) {
+	while (blk->fifo_available && qup->pos < msg->len) {
 		if ((idx & 1) == 0) {
-			/* Check that FIFO have data */
-			ret = qup_i2c_wait_ready(qup, QUP_IN_NOT_EMPTY,
-						 SET_BIT, 4 * ONE_BYTE);
-			if (ret)
-				return ret;
-
 			/* Reading 2 words at time */
 			val = readl(qup->base + QUP_IN_FIFO_BASE);
-
 			msg->buf[qup->pos++] = val & 0xFF;
 		} else {
 			msg->buf[qup->pos++] = val >> QUP_MSW_SHIFT;
 		}
+		idx++;
+		blk->fifo_available--;
 	}
 
-	return ret;
+	if (qup->pos == msg->len)
+		blk->rx_bytes_read = true;
 }
 
 static int qup_i2c_read_fifo_v2(struct qup_i2c_dev *qup,
@@ -1224,49 +1218,130 @@ static int qup_i2c_read_one_v2(struct qup_i2c_dev *qup, struct i2c_msg *msg)
 	return ret;
 }
 
-static int qup_i2c_read_one(struct qup_i2c_dev *qup, struct i2c_msg *msg)
+static void qup_i2c_write_rx_tags_v1(struct qup_i2c_dev *qup)
 {
+	struct i2c_msg *msg = qup->msg;
+	u32 addr, len, val;
+
+	addr = i2c_8bit_addr_from_msg(msg);
+
+	/* 0 is used to specify a length 256 (QUP_READ_LIMIT) */
+	len = (msg->len == QUP_READ_LIMIT) ? 0 : msg->len;
+
+	val = ((QUP_TAG_REC | len) << QUP_MSW_SHIFT) | QUP_TAG_START | addr;
+	writel(val, qup->base + QUP_OUT_FIFO_BASE);
+}
+
+static void qup_i2c_conf_v1(struct qup_i2c_dev *qup)
+{
+	struct qup_i2c_block *blk = &qup->blk;
+	u32 qup_config = I2C_MINI_CORE | I2C_N_VAL;
+	u32 io_mode = QUP_REPACK_EN;
+
+	blk->is_tx_blk_mode =
+		blk->total_tx_len > qup->out_fifo_sz ? true : false;
+	blk->is_rx_blk_mode =
+		blk->total_rx_len > qup->in_fifo_sz ? true : false;
+
+	if (blk->is_tx_blk_mode) {
+		io_mode |= QUP_OUTPUT_BLK_MODE;
+		writel(0, qup->base + QUP_MX_WRITE_CNT);
+		writel(blk->total_tx_len, qup->base + QUP_MX_OUTPUT_CNT);
+	} else {
+		writel(0, qup->base + QUP_MX_OUTPUT_CNT);
+		writel(blk->total_tx_len, qup->base + QUP_MX_WRITE_CNT);
+	}
+
+	if (blk->total_rx_len) {
+		if (blk->is_rx_blk_mode) {
+			io_mode |= QUP_INPUT_BLK_MODE;
+			writel(0, qup->base + QUP_MX_READ_CNT);
+			writel(blk->total_rx_len, qup->base + QUP_MX_INPUT_CNT);
+		} else {
+			writel(0, qup->base + QUP_MX_INPUT_CNT);
+			writel(blk->total_rx_len, qup->base + QUP_MX_READ_CNT);
+		}
+	} else {
+		qup_config |= QUP_NO_INPUT;
+	}
+
+	writel(qup_config, qup->base + QUP_CONFIG);
+	writel(io_mode, qup->base + QUP_IO_MODE);
+}
+
+static void qup_i2c_clear_blk_v1(struct qup_i2c_block *blk)
+{
+	blk->tx_fifo_free = 0;
+	blk->fifo_available = 0;
+	blk->rx_bytes_read = false;
+}
+
+static int qup_i2c_conf_xfer_v1(struct qup_i2c_dev *qup, bool is_rx)
+{
+	struct qup_i2c_block *blk = &qup->blk;
 	int ret;
 
-	qup->msg = msg;
-	qup->pos  = 0;
-
-	enable_irq(qup->irq);
-	qup_i2c_set_read_mode(qup, msg->len);
-
+	qup_i2c_clear_blk_v1(blk);
+	qup_i2c_conf_v1(qup);
 	ret = qup_i2c_change_state(qup, QUP_RUN_STATE);
 	if (ret)
-		goto err;
+		return ret;
 
 	writel(qup->clk_ctl, qup->base + QUP_I2C_CLK_CTL);
 
 	ret = qup_i2c_change_state(qup, QUP_PAUSE_STATE);
 	if (ret)
-		goto err;
+		return ret;
 
-	qup_i2c_issue_read(qup, msg);
+	reinit_completion(&qup->xfer);
+	enable_irq(qup->irq);
+	if (!blk->is_tx_blk_mode) {
+		blk->tx_fifo_free = qup->out_fifo_sz;
+
+		if (is_rx)
+			qup_i2c_write_rx_tags_v1(qup);
+		else
+			qup_i2c_write_tx_fifo_v1(qup);
+	}
 
 	ret = qup_i2c_change_state(qup, QUP_RUN_STATE);
 	if (ret)
 		goto err;
 
-	do {
-		ret = qup_i2c_wait_for_complete(qup, msg);
-		if (ret)
-			goto err;
+	ret = qup_i2c_wait_for_complete(qup, qup->msg);
+	if (ret)
+		goto err;
 
-		ret = qup_i2c_read_fifo(qup, msg);
-		if (ret)
-			goto err;
-	} while (qup->pos < msg->len);
+	ret = qup_i2c_bus_active(qup, ONE_BYTE);
 
 err:
 	disable_irq(qup->irq);
-	qup->msg = NULL;
-
 	return ret;
 }
 
+static int qup_i2c_write_one(struct qup_i2c_dev *qup)
+{
+	struct i2c_msg *msg = qup->msg;
+	struct qup_i2c_block *blk = &qup->blk;
+
+	qup->pos = 0;
+	blk->total_tx_len = msg->len + 1;
+	blk->total_rx_len = 0;
+
+	return qup_i2c_conf_xfer_v1(qup, false);
+}
+
+static int qup_i2c_read_one(struct qup_i2c_dev *qup)
+{
+	struct qup_i2c_block *blk = &qup->blk;
+
+	qup->pos = 0;
+	blk->total_tx_len = 2;
+	blk->total_rx_len = qup->msg->len;
+
+	return qup_i2c_conf_xfer_v1(qup, true);
+}
+
 static int qup_i2c_xfer(struct i2c_adapter *adap,
 			struct i2c_msg msgs[],
 			int num)
@@ -1305,10 +1380,11 @@ static int qup_i2c_xfer(struct i2c_adapter *adap,
 			goto out;
 		}
 
+		qup->msg = &msgs[idx];
 		if (msgs[idx].flags & I2C_M_RD)
-			ret = qup_i2c_read_one(qup, &msgs[idx]);
+			ret = qup_i2c_read_one(qup);
 		else
-			ret = qup_i2c_write_one(qup, &msgs[idx]);
+			ret = qup_i2c_write_one(qup);
 
 		if (ret)
 			break;
@@ -1487,6 +1563,10 @@ static int qup_i2c_probe(struct platform_device *pdev)
 	if (of_device_is_compatible(pdev->dev.of_node, "qcom,i2c-qup-v1.1.1")) {
 		qup->adap.algo = &qup_i2c_algo;
 		qup->adap.quirks = &qup_i2c_quirks;
+		qup->is_qup_v1 = true;
+		qup->write_tx_fifo = qup_i2c_write_tx_fifo_v1;
+		qup->read_rx_fifo = qup_i2c_read_rx_fifo_v1;
+		qup->write_rx_tags = qup_i2c_write_rx_tags_v1;
 	} else {
 		qup->adap.algo = &qup_i2c_algo_v2;
 		ret = qup_i2c_req_dma(qup);
-- 
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