[PATCH] Fix broken FSL eSPI driver.

[Kenth Eriksson <kenth.eriksson-SNLAxHN9vbdl57MIdRCFDg@public.gmane.org>]

The eSPI driver does not work on our P2010 board with an 8-bit SPI slave.

- The transmission length is always twice the expected. The length is set to (n_tx + n_rx), which is incorrect for a full duplex SPI interface.
- Bytes and characters are mixed up. The len field in struct spi_transfer is counted in bytes, while the TRANLEN field in the eSPI controller is counted in characters, and bits_per_word si the relation between the two.
- The bytes received from the controller are written at the wrong offset in the driver's receive buffer.
- The interrupt handler calculation of remaining bytes is incorrect.

This fix is based on a previous patch that was not included to lack of response, see http://sourceforge.net/mailarchive/message.php?msg_id=27820036

Signed-off-by: Kenth Eriksson <kenth.eriksson-SNLAxHN9vbdl57MIdRCFDg@public.gmane.org>
---
 drivers/spi/spi-fsl-espi.c |   36 ++++++++++++++++++++++++++----------
 drivers/spi/spi-fsl-lib.h  |    1 +
 2 files changed, 27 insertions(+), 10 deletions(-)

diff --git a/drivers/spi/spi-fsl-espi.c b/drivers/spi/spi-fsl-espi.c
index 249d244..2c4224b 100644
--- a/drivers/spi/spi-fsl-espi.c
+++ b/drivers/spi/spi-fsl-espi.c
@@ -232,21 +232,32 @@ static int fsl_espi_bufs(struct spi_device *spi, struct spi_transfer *t)
 		bits_per_word = t->bits_per_word;
 
 	mpc8xxx_spi->len = t->len;
-	len = roundup(len, 4) / 4;
 
 	mpc8xxx_spi->tx = t->tx_buf;
 	mpc8xxx_spi->rx = t->rx_buf;
+	mpc8xxx_spi->bits_per_word = bits_per_word;
 
 	INIT_COMPLETION(mpc8xxx_spi->done);
 
+	/* Convert between t->len (in bytes) and count (in
+	 * characters). For character lengths of 9 to 16 bits, each
+	 * character occupies 2 bytes in Rx/Tx FIFO.
+	 */
+	if (bits_per_word <= 8)
+		len = t->len;
+	else if (bits_per_word <= 16)
+		len = t->len >> 1;
+	else
+		return -EINVAL;
+
 	/* Set SPCOM[CS] and SPCOM[TRANLEN] field */
-	if ((t->len - 1) > SPCOM_TRANLEN_MAX) {
+	if ((len - 1) > SPCOM_TRANLEN_MAX) {
 		dev_err(mpc8xxx_spi->dev, "Transaction length (%d)"
-				" beyond the SPCOM[TRANLEN] field\n", t->len);
+			" beyond the SPCOM[TRANLEN] field\n", len);
 		return -EINVAL;
 	}
 	mpc8xxx_spi_write_reg(&reg_base->command,
-		(SPCOM_CS(spi->chip_select) | SPCOM_TRANLEN(t->len - 1)));
+		(SPCOM_CS(spi->chip_select) | SPCOM_TRANLEN(len - 1)));
 
 	ret = fsl_espi_cpu_bufs(mpc8xxx_spi, t, len);
 	if (ret)
@@ -405,12 +416,12 @@ static void fsl_espi_rw_trans(struct spi_message *m,
 
 		espi_trans->n_tx = n_tx;
 		espi_trans->n_rx = trans_len;
-		espi_trans->len = trans_len + n_tx;
+		espi_trans->len = n_tx;
 		espi_trans->tx_buf = local_buf;
 		espi_trans->rx_buf = local_buf + n_tx;
 		fsl_espi_do_trans(m, espi_trans);
 
-		memcpy(rx_buf + pos, espi_trans->rx_buf + n_tx, trans_len);
+		memcpy(rx_buf + pos, espi_trans->rx_buf, trans_len);
 
 		if (loop > 0)
 			espi_trans->actual_length += espi_trans->len - n_tx;
@@ -440,7 +451,7 @@ static void fsl_espi_do_one_msg(struct spi_message *m)
 
 	espi_trans.n_tx = n_tx;
 	espi_trans.n_rx = n_rx;
-	espi_trans.len = n_tx + n_rx;
+	espi_trans.len = n_tx;
 	espi_trans.actual_length = 0;
 	espi_trans.status = 0;
 
@@ -522,6 +533,7 @@ void fsl_espi_cpu_irq(struct mpc8xxx_spi *mspi, u32 events)
 
 		if (mspi->len >= 4) {
 			rx_data = mpc8xxx_spi_read_reg(&reg_base->receive);
+			mspi->len -= 4;
 		} else {
 			tmp = mspi->len;
 			rx_data = 0;
@@ -531,10 +543,9 @@ void fsl_espi_cpu_irq(struct mpc8xxx_spi *mspi, u32 events)
 			}
 
 			rx_data <<= (4 - mspi->len) * 8;
+			mspi->len = 0;
 		}
 
-		mspi->len -= 4;
-
 		if (mspi->rx)
 			mspi->get_rx(rx_data, mspi);
 	}
@@ -554,7 +565,12 @@ void fsl_espi_cpu_irq(struct mpc8xxx_spi *mspi, u32 events)
 	/* Clear the events */
 	mpc8xxx_spi_write_reg(&reg_base->event, events);
 
-	mspi->count -= 1;
+	if (mspi->bits_per_word <= 8) {
+		mspi->count = mspi->len;
+	} else if (mspi->bits_per_word <= 16) {
+		mspi->count = mspi->len >> 1;
+	}
+
 	if (mspi->count) {
 		u32 word = mspi->get_tx(mspi);
 
diff --git a/drivers/spi/spi-fsl-lib.h b/drivers/spi/spi-fsl-lib.h
index cbe881b..53c7cb6 100644
--- a/drivers/spi/spi-fsl-lib.h
+++ b/drivers/spi/spi-fsl-lib.h
@@ -57,6 +57,7 @@ struct mpc8xxx_spi {
 	void (*spi_remove) (struct mpc8xxx_spi *mspi);
 
 	unsigned int count;
+	u8 bits_per_word;
 	unsigned int irq;
 
 	unsigned nsecs;		/* (clock cycle time)/2 */
-- 
1.7.3.4


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