1 files changed, 37 insertions, 32 deletions

diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
index 88c6efeebe06..0c7bd1aa7719 100644
--- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
+++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
@@ -2,8 +2,8 @@
 //
 // mcp251xfd - Microchip MCP251xFD Family CAN controller driver
 //
-// Copyright (c) 2019, 2020 Pengutronix,
-//                          Marc Kleine-Budde <kernel@pengutronix.de>
+// Copyright (c) 2019, 2020, 2021 Pengutronix,
+//               Marc Kleine-Budde <kernel@pengutronix.de>
 //
 // Based on:
 //
@@ -330,6 +330,7 @@ static void mcp251xfd_ring_init(struct mcp251xfd_priv *priv)
 	struct mcp251xfd_tx_ring *tx_ring;
 	struct mcp251xfd_rx_ring *rx_ring, *prev_rx_ring = NULL;
 	struct mcp251xfd_tx_obj *tx_obj;
+	struct spi_transfer *xfer;
 	u32 val;
 	u16 addr;
 	u8 len;
@@ -347,8 +348,6 @@ static void mcp251xfd_ring_init(struct mcp251xfd_priv *priv)
 					      addr, val, val);
 
 	for (j = 0; j < ARRAY_SIZE(tef_ring->uinc_xfer); j++) {
-		struct spi_transfer *xfer;
-
 		xfer = &tef_ring->uinc_xfer[j];
 		xfer->tx_buf = &tef_ring->uinc_buf;
 		xfer->len = len;
@@ -357,6 +356,15 @@ static void mcp251xfd_ring_init(struct mcp251xfd_priv *priv)
 		xfer->cs_change_delay.unit = SPI_DELAY_UNIT_NSECS;
 	}
 
+	/* "cs_change == 1" on the last transfer results in an active
+	 * chip select after the complete SPI message. This causes the
+	 * controller to interpret the next register access as
+	 * data. Set "cs_change" of the last transfer to "0" to
+	 * properly deactivate the chip select at the end of the
+	 * message.
+	 */
+	xfer->cs_change = 0;
+
 	/* TX */
 	tx_ring = priv->tx;
 	tx_ring->head = 0;
@@ -397,8 +405,6 @@ static void mcp251xfd_ring_init(struct mcp251xfd_priv *priv)
 						      addr, val, val);
 
 		for (j = 0; j < ARRAY_SIZE(rx_ring->uinc_xfer); j++) {
-			struct spi_transfer *xfer;
-
 			xfer = &rx_ring->uinc_xfer[j];
 			xfer->tx_buf = &rx_ring->uinc_buf;
 			xfer->len = len;
@@ -406,6 +412,15 @@ static void mcp251xfd_ring_init(struct mcp251xfd_priv *priv)
 			xfer->cs_change_delay.value = 0;
 			xfer->cs_change_delay.unit = SPI_DELAY_UNIT_NSECS;
 		}
+
+		/* "cs_change == 1" on the last transfer results in an
+		 * active chip select after the complete SPI
+		 * message. This causes the controller to interpret
+		 * the next register access as data. Set "cs_change"
+		 * of the last transfer to "0" to properly deactivate
+		 * the chip select at the end of the message.
+		 */
+		xfer->cs_change = 0;
 	}
 }
 
@@ -1366,25 +1381,20 @@ static int mcp251xfd_handle_tefif(struct mcp251xfd_priv *priv)
 	if (len) {
 		struct mcp251xfd_tef_ring *ring = priv->tef;
 		struct mcp251xfd_tx_ring *tx_ring = priv->tx;
-		struct spi_transfer *last_xfer;
+		int offset;
 
 		/* Increment the TEF FIFO tail pointer 'len' times in
 		 * a single SPI message.
 		 *
 		 * Note:
-		 *
-		 * "cs_change == 1" on the last transfer results in an
-		 * active chip select after the complete SPI
-		 * message. This causes the controller to interpret
-		 * the next register access as data. Temporary set
-		 * "cs_change" of the last transfer to "0" to properly
-		 * deactivate the chip select at the end of the
-		 * message.
+		 * Calculate offset, so that the SPI transfer ends on
+		 * the last message of the uinc_xfer array, which has
+		 * "cs_change == 0", to properly deactivate the chip
+		 * select.
 		 */
-		last_xfer = &ring->uinc_xfer[len - 1];
-		last_xfer->cs_change = 0;
-		err = spi_sync_transfer(priv->spi, ring->uinc_xfer, len);
-		last_xfer->cs_change = 1;
+		offset = ARRAY_SIZE(ring->uinc_xfer) - len;
+		err = spi_sync_transfer(priv->spi,
+					ring->uinc_xfer + offset, len);
 		if (err)
 			return err;
 
@@ -1536,7 +1546,7 @@ mcp251xfd_handle_rxif_ring(struct mcp251xfd_priv *priv,
 		return err;
 
 	while ((len = mcp251xfd_get_rx_linear_len(ring))) {
-		struct spi_transfer *last_xfer;
+		int offset;
 
 		rx_tail = mcp251xfd_get_rx_tail(ring);
 
@@ -1557,19 +1567,14 @@ mcp251xfd_handle_rxif_ring(struct mcp251xfd_priv *priv,
 		 * single SPI message.
 		 *
 		 * Note:
-		 *
-		 * "cs_change == 1" on the last transfer results in an
-		 * active chip select after the complete SPI
-		 * message. This causes the controller to interpret
-		 * the next register access as data. Temporary set
-		 * "cs_change" of the last transfer to "0" to properly
-		 * deactivate the chip select at the end of the
-		 * message.
+		 * Calculate offset, so that the SPI transfer ends on
+		 * the last message of the uinc_xfer array, which has
+		 * "cs_change == 0", to properly deactivate the chip
+		 * select.
 		 */
-		last_xfer = &ring->uinc_xfer[len - 1];
-		last_xfer->cs_change = 0;
-		err = spi_sync_transfer(priv->spi, ring->uinc_xfer, len);
-		last_xfer->cs_change = 1;
+		offset = ARRAY_SIZE(ring->uinc_xfer) - len;
+		err = spi_sync_transfer(priv->spi,
+					ring->uinc_xfer + offset, len);
 		if (err)
 			return err;