[PATCH 1/1] spi: bcm-qspi: Added mspi read fallback in bcm_qspi_flash_read()

[Kamal Dasu <kdasu.kdev@gmail.com>]

Added mspi read fallback under certain circumstances like unaligned
buffer, address on short reads. Also takes care of version 3.0 spi
controller where flash address crosses 4MB boundary on transfers the
driver resorts to mspi reads.

Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
---
 drivers/spi/spi-bcm-qspi.c | 116 +++++++++++++++++++++++++++++++++------------
 1 file changed, 85 insertions(+), 31 deletions(-)

diff --git a/drivers/spi/spi-bcm-qspi.c b/drivers/spi/spi-bcm-qspi.c
index 14f9dea..b50b6df 100644
--- a/drivers/spi/spi-bcm-qspi.c
+++ b/drivers/spi/spi-bcm-qspi.c
@@ -192,9 +192,11 @@ struct bcm_qspi_dev_id {
 	void *dev;
 };
 
+
 struct qspi_trans {
 	struct spi_transfer *trans;
 	int byte;
+	bool mspi_last_trans;
 };
 
 struct bcm_qspi {
@@ -616,6 +618,16 @@ static int bcm_qspi_setup(struct spi_device *spi)
 	return 0;
 }
 
+static bool bcm_qspi_mspi_transfer_is_last(struct bcm_qspi *qspi,
+					   struct qspi_trans *qt)
+{
+	if (qt->mspi_last_trans &&
+	    spi_transfer_is_last(qspi->master, qt->trans))
+		return true;
+	else
+		return false;
+}
+
 static int update_qspi_trans_byte_count(struct bcm_qspi *qspi,
 					struct qspi_trans *qt, int flags)
 {
@@ -629,7 +641,6 @@ static int update_qspi_trans_byte_count(struct bcm_qspi *qspi,
 
 	if (qt->byte >= qt->trans->len) {
 		/* we're at the end of the spi_transfer */
-
 		/* in TX mode, need to pause for a delay or CS change */
 		if (qt->trans->delay_usecs &&
 		    (flags & TRANS_STATUS_BREAK_DELAY))
@@ -641,7 +652,7 @@ static int update_qspi_trans_byte_count(struct bcm_qspi *qspi,
 			goto done;
 
 		dev_dbg(&qspi->pdev->dev, "advance msg exit\n");
-		if (spi_transfer_is_last(qspi->master, qt->trans))
+		if (bcm_qspi_mspi_transfer_is_last(qspi, qt))
 			ret = TRANS_STATUS_BREAK_EOM;
 		else
 			ret = TRANS_STATUS_BREAK_NO_BYTES;
@@ -885,6 +896,76 @@ static int bcm_qspi_bspi_flash_read(struct spi_device *spi,
 	return ret;
 }
 
+static int bcm_qspi_transfer_one(struct spi_master *master,
+				 struct spi_device *spi,
+				 struct spi_transfer *trans)
+{
+	struct bcm_qspi *qspi = spi_master_get_devdata(master);
+	int slots;
+	unsigned long timeo = msecs_to_jiffies(100);
+
+	bcm_qspi_chip_select(qspi, spi->chip_select);
+	qspi->trans_pos.trans = trans;
+	qspi->trans_pos.byte = 0;
+
+	while (qspi->trans_pos.byte < trans->len) {
+		reinit_completion(&qspi->mspi_done);
+
+		slots = write_to_hw(qspi, spi);
+		if (!wait_for_completion_timeout(&qspi->mspi_done, timeo)) {
+			dev_err(&qspi->pdev->dev, "timeout waiting for MSPI\n");
+			return -ETIMEDOUT;
+		}
+
+		read_from_hw(qspi, slots);
+	}
+
+	return 0;
+}
+
+static int bcm_qspi_mspi_flash_read(struct spi_device *spi,
+				    struct spi_flash_read_message *msg)
+{
+	struct bcm_qspi *qspi = spi_master_get_devdata(spi->master);
+	struct spi_transfer t[2];
+	u8 cmd[6];
+	int ret;
+
+	memset(cmd, 0, sizeof(cmd));
+	memset(t, 0, sizeof(t));
+
+	/* tx */
+	/* opcode is in cmd[0] */
+	cmd[0] = msg->read_opcode;
+	cmd[1] = msg->from >> (msg->addr_width * 8 -  8);
+	cmd[2] = msg->from >> (msg->addr_width * 8 - 16);
+	cmd[3] = msg->from >> (msg->addr_width * 8 - 24);
+	cmd[4] = msg->from >> (msg->addr_width * 8 - 32);
+	t[0].tx_buf = cmd;
+	t[0].len = msg->addr_width + msg->dummy_bytes + 1;
+	t[0].bits_per_word = spi->bits_per_word;
+	t[0].tx_nbits = msg->opcode_nbits;
+	/* lets mspi know that this is not last transfer */
+	qspi->trans_pos.mspi_last_trans = false;
+	ret = bcm_qspi_transfer_one(spi->master, spi, &t[0]);
+
+	/* rx */
+	qspi->trans_pos.mspi_last_trans = true;
+	if (!ret) {
+		/* rx */
+		t[1].rx_buf = msg->buf;
+		t[1].len = msg->len;
+		t[1].rx_nbits =  msg->data_nbits;
+		t[1].bits_per_word = spi->bits_per_word;
+		ret = bcm_qspi_transfer_one(spi->master, spi, &t[1]);
+	}
+
+	if (!ret)
+		msg->retlen = msg->len;
+
+	return ret;
+}
+
 static int bcm_qspi_flash_read(struct spi_device *spi,
 			       struct spi_flash_read_message *msg)
 {
@@ -918,8 +999,7 @@ static int bcm_qspi_flash_read(struct spi_device *spi,
 		mspi_read = true;
 
 	if (mspi_read)
-		/* this will make the m25p80 read to fallback to mspi read */
-		return -EAGAIN;
+		return bcm_qspi_mspi_flash_read(spi, msg);
 
 	io_width = msg->data_nbits ? msg->data_nbits : SPI_NBITS_SINGLE;
 	addrlen = msg->addr_width;
@@ -931,33 +1011,6 @@ static int bcm_qspi_flash_read(struct spi_device *spi,
 	return ret;
 }
 
-static int bcm_qspi_transfer_one(struct spi_master *master,
-				 struct spi_device *spi,
-				 struct spi_transfer *trans)
-{
-	struct bcm_qspi *qspi = spi_master_get_devdata(master);
-	int slots;
-	unsigned long timeo = msecs_to_jiffies(100);
-
-	bcm_qspi_chip_select(qspi, spi->chip_select);
-	qspi->trans_pos.trans = trans;
-	qspi->trans_pos.byte = 0;
-
-	while (qspi->trans_pos.byte < trans->len) {
-		reinit_completion(&qspi->mspi_done);
-
-		slots = write_to_hw(qspi, spi);
-		if (!wait_for_completion_timeout(&qspi->mspi_done, timeo)) {
-			dev_err(&qspi->pdev->dev, "timeout waiting for MSPI\n");
-			return -ETIMEDOUT;
-		}
-
-		read_from_hw(qspi, slots);
-	}
-
-	return 0;
-}
-
 static void bcm_qspi_cleanup(struct spi_device *spi)
 {
 	struct bcm_qspi_parms *xp = spi_get_ctldata(spi);
@@ -1187,6 +1240,7 @@ int bcm_qspi_probe(struct platform_device *pdev,
 	qspi->pdev = pdev;
 	qspi->trans_pos.trans = NULL;
 	qspi->trans_pos.byte = 0;
+	qspi->trans_pos.mspi_last_trans = true;
 	qspi->master = master;
 
 	master->bus_num = -1;
-- 
1.9.1