Applied "spi: armada-3700: Fix padding when sending not 4-byte aligned data" to the spi tree

[Mark Brown <broonie@xxxxxxxxxx>]

The patch

   spi: armada-3700: Fix padding when sending not 4-byte aligned data

has been applied to the spi tree at

   git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git 

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

>From 6fd6fd68c9e2f3a206a098ef57b1d5548f9d00d1 Mon Sep 17 00:00:00 2001
From: Zachary Zhang <zhangzg@xxxxxxxxxxx>
Date: Wed, 13 Sep 2017 18:21:39 +0200
Subject: [PATCH] spi: armada-3700: Fix padding when sending not 4-byte aligned
 data

In 4-byte transfer mode, extra padding/dummy bytes '0xff' would be
sent in write operation if TX data is not 4-byte aligned since the
SPI data register is always shifted out as whole 4 bytes.

Fix this by using the header count feature that allows to transfer 0 to
4 bytes. Use it to actually send the first 1 to 3 bytes of data before
the rest of the buffer that will hence be 4-byte aligned.

Signed-off-by: Zachary Zhang <zhangzg@xxxxxxxxxxx>
Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
---
 drivers/spi/spi-armada-3700.c | 135 +++++++++++++-----------------------------
 1 file changed, 41 insertions(+), 94 deletions(-)

diff --git a/drivers/spi/spi-armada-3700.c b/drivers/spi/spi-armada-3700.c
index a28702b1fa05..9172cb2d2e7a 100644
--- a/drivers/spi/spi-armada-3700.c
+++ b/drivers/spi/spi-armada-3700.c
@@ -99,11 +99,6 @@
 /* A3700_SPI_IF_TIME_REG */
 #define A3700_SPI_CLK_CAPT_EDGE		BIT(7)
 
-/* Flags and macros for struct a3700_spi */
-#define A3700_INSTR_CNT			1
-#define A3700_ADDR_CNT			3
-#define A3700_DUMMY_CNT			1
-
 struct a3700_spi {
 	struct spi_master *master;
 	void __iomem *base;
@@ -117,9 +112,6 @@ struct a3700_spi {
 	u8 byte_len;
 	u32 wait_mask;
 	struct completion done;
-	u32 addr_cnt;
-	u32 instr_cnt;
-	size_t hdr_cnt;
 };
 
 static u32 spireg_read(struct a3700_spi *a3700_spi, u32 offset)
@@ -449,59 +441,43 @@ static void a3700_spi_set_cs(struct spi_device *spi, bool enable)
 
 static void a3700_spi_header_set(struct a3700_spi *a3700_spi)
 {
-	u32 instr_cnt = 0, addr_cnt = 0, dummy_cnt = 0;
+	unsigned int addr_cnt;
 	u32 val = 0;
 
 	/* Clear the header registers */
 	spireg_write(a3700_spi, A3700_SPI_IF_INST_REG, 0);
 	spireg_write(a3700_spi, A3700_SPI_IF_ADDR_REG, 0);
 	spireg_write(a3700_spi, A3700_SPI_IF_RMODE_REG, 0);
+	spireg_write(a3700_spi, A3700_SPI_IF_HDR_CNT_REG, 0);
 
 	/* Set header counters */
 	if (a3700_spi->tx_buf) {
-		if (a3700_spi->buf_len <= a3700_spi->instr_cnt) {
-			instr_cnt = a3700_spi->buf_len;
-		} else if (a3700_spi->buf_len <= (a3700_spi->instr_cnt +
-						  a3700_spi->addr_cnt)) {
-			instr_cnt = a3700_spi->instr_cnt;
-			addr_cnt = a3700_spi->buf_len - instr_cnt;
-		} else if (a3700_spi->buf_len <= a3700_spi->hdr_cnt) {
-			instr_cnt = a3700_spi->instr_cnt;
-			addr_cnt = a3700_spi->addr_cnt;
-			/* Need to handle the normal write case with 1 byte
-			 * data
-			 */
-			if (!a3700_spi->tx_buf[instr_cnt + addr_cnt])
-				dummy_cnt = a3700_spi->buf_len - instr_cnt -
-					    addr_cnt;
+		/*
+		 * when tx data is not 4 bytes aligned, there will be unexpected
+		 * bytes out of SPI output register, since it always shifts out
+		 * as whole 4 bytes. This might cause incorrect transaction with
+		 * some devices. To avoid that, use SPI header count feature to
+		 * transfer up to 3 bytes of data first, and then make the rest
+		 * of data 4-byte aligned.
+		 */
+		addr_cnt = a3700_spi->buf_len % 4;
+		if (addr_cnt) {
+			val = (addr_cnt & A3700_SPI_ADDR_CNT_MASK)
+				<< A3700_SPI_ADDR_CNT_BIT;
+			spireg_write(a3700_spi, A3700_SPI_IF_HDR_CNT_REG, val);
+
+			/* Update the buffer length to be transferred */
+			a3700_spi->buf_len -= addr_cnt;
+
+			/* transfer 1~3 bytes through address count */
+			val = 0;
+			while (addr_cnt--) {
+				val = (val << 8) | a3700_spi->tx_buf[0];
+				a3700_spi->tx_buf++;
+			}
+			spireg_write(a3700_spi, A3700_SPI_IF_ADDR_REG, val);
 		}
-		val |= ((instr_cnt & A3700_SPI_INSTR_CNT_MASK)
-			<< A3700_SPI_INSTR_CNT_BIT);
-		val |= ((addr_cnt & A3700_SPI_ADDR_CNT_MASK)
-			<< A3700_SPI_ADDR_CNT_BIT);
-		val |= ((dummy_cnt & A3700_SPI_DUMMY_CNT_MASK)
-			<< A3700_SPI_DUMMY_CNT_BIT);
 	}
-	spireg_write(a3700_spi, A3700_SPI_IF_HDR_CNT_REG, val);
-
-	/* Update the buffer length to be transferred */
-	a3700_spi->buf_len -= (instr_cnt + addr_cnt + dummy_cnt);
-
-	/* Set Instruction */
-	val = 0;
-	while (instr_cnt--) {
-		val = (val << 8) | a3700_spi->tx_buf[0];
-		a3700_spi->tx_buf++;
-	}
-	spireg_write(a3700_spi, A3700_SPI_IF_INST_REG, val);
-
-	/* Set Address */
-	val = 0;
-	while (addr_cnt--) {
-		val = (val << 8) | a3700_spi->tx_buf[0];
-		a3700_spi->tx_buf++;
-	}
-	spireg_write(a3700_spi, A3700_SPI_IF_ADDR_REG, val);
 }
 
 static int a3700_is_wfifo_full(struct a3700_spi *a3700_spi)
@@ -515,35 +491,12 @@ static int a3700_is_wfifo_full(struct a3700_spi *a3700_spi)
 static int a3700_spi_fifo_write(struct a3700_spi *a3700_spi)
 {
 	u32 val;
-	int i = 0;
 
 	while (!a3700_is_wfifo_full(a3700_spi) && a3700_spi->buf_len) {
-		val = 0;
-		if (a3700_spi->buf_len >= 4) {
-			val = cpu_to_le32(*(u32 *)a3700_spi->tx_buf);
-			spireg_write(a3700_spi, A3700_SPI_DATA_OUT_REG, val);
-
-			a3700_spi->buf_len -= 4;
-			a3700_spi->tx_buf += 4;
-		} else {
-			/*
-			 * If the remained buffer length is less than 4-bytes,
-			 * we should pad the write buffer with all ones. So that
-			 * it avoids overwrite the unexpected bytes following
-			 * the last one.
-			 */
-			val = GENMASK(31, 0);
-			while (a3700_spi->buf_len) {
-				val &= ~(0xff << (8 * i));
-				val |= *a3700_spi->tx_buf++ << (8 * i);
-				i++;
-				a3700_spi->buf_len--;
-
-				spireg_write(a3700_spi, A3700_SPI_DATA_OUT_REG,
-					     val);
-			}
-			break;
-		}
+		val = cpu_to_le32(*(u32 *)a3700_spi->tx_buf);
+		spireg_write(a3700_spi, A3700_SPI_DATA_OUT_REG, val);
+		a3700_spi->buf_len -= 4;
+		a3700_spi->tx_buf += 4;
 	}
 
 	return 0;
@@ -648,9 +601,6 @@ static int a3700_spi_transfer_one(struct spi_master *master,
 	a3700_spi->rx_buf  = xfer->rx_buf;
 	a3700_spi->buf_len = xfer->len;
 
-	/* SPI transfer headers */
-	a3700_spi_header_set(a3700_spi);
-
 	if (xfer->tx_buf)
 		nbits = xfer->tx_nbits;
 	else if (xfer->rx_buf)
@@ -658,6 +608,12 @@ static int a3700_spi_transfer_one(struct spi_master *master,
 
 	a3700_spi_pin_mode_set(a3700_spi, nbits, xfer->rx_buf ? true : false);
 
+	/* Flush the FIFOs */
+	a3700_spi_fifo_flush(a3700_spi);
+
+	/* Transfer first bytes of data when buffer is not 4-byte aligned */
+	a3700_spi_header_set(a3700_spi);
+
 	if (xfer->rx_buf) {
 		/* Set read data length */
 		spireg_write(a3700_spi, A3700_SPI_IF_DIN_CNT_REG,
@@ -736,16 +692,11 @@ static int a3700_spi_transfer_one(struct spi_master *master,
 				dev_err(&spi->dev, "wait wfifo empty timed out\n");
 				return -ETIMEDOUT;
 			}
-		} else {
-			/*
-			 * If the instruction in SPI_INSTR does not require data
-			 * to be written to the SPI device, wait until SPI_RDY
-			 * is 1 for the SPI interface to be in idle.
-			 */
-			if (!a3700_spi_transfer_wait(spi, A3700_SPI_XFER_RDY)) {
-				dev_err(&spi->dev, "wait xfer ready timed out\n");
-				return -ETIMEDOUT;
-			}
+		}
+
+		if (!a3700_spi_transfer_wait(spi, A3700_SPI_XFER_RDY)) {
+			dev_err(&spi->dev, "wait xfer ready timed out\n");
+			return -ETIMEDOUT;
 		}
 
 		val = spireg_read(a3700_spi, A3700_SPI_IF_CFG_REG);
@@ -837,10 +788,6 @@ static int a3700_spi_probe(struct platform_device *pdev)
 	memset(spi, 0, sizeof(struct a3700_spi));
 
 	spi->master = master;
-	spi->instr_cnt = A3700_INSTR_CNT;
-	spi->addr_cnt = A3700_ADDR_CNT;
-	spi->hdr_cnt = A3700_INSTR_CNT + A3700_ADDR_CNT +
-		       A3700_DUMMY_CNT;
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	spi->base = devm_ioremap_resource(dev, res);
-- 
2.13.2

--
To unsubscribe from this list: send the line "unsubscribe linux-spi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html