[U-Boot] [PATCH] MX28: SPI: Limit the DMA transfer length

[Marek Vasut]

The upper limit for DMA transfer length on MX28 is 0x4000 bytes,
otherwise the DMA refuses to operate.

Signed-off-by: Marek Vasut <marex at denx.de>
Cc: Fabio Estevam <festevam at gmail.com>
Cc: Otavio Salvador <otavio at ossystems.com.br>
Cc: Stefano Babic <sbabic at denx.de>
---
 drivers/spi/mxs_spi.c |   31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/drivers/spi/mxs_spi.c b/drivers/spi/mxs_spi.c
index a037c13..fb6a167 100644
--- a/drivers/spi/mxs_spi.c
+++ b/drivers/spi/mxs_spi.c
@@ -287,9 +287,9 @@ static int mxs_spi_xfer_dma(struct mxs_spi_slave *slave,
 int spi_xfer(struct spi_slave *slave, unsigned int bitlen,
 		const void *dout, void *din, unsigned long flags)
 {
-	struct mxs_spi_slave *mxs_slave = to_mxs_slave(slave);
-	struct mxs_ssp_regs *ssp_regs = mxs_slave->regs;
-	int len = bitlen / 8;
+	struct mxs_spi_slave *sslave = to_mxs_slave(slave);
+	struct mxs_ssp_regs *regs = sslave->regs;
+	int len = bitlen / 8, tl, ret;
 	char dummy;
 	int write = 0;
 	char *data = NULL;
@@ -335,11 +335,24 @@ int spi_xfer(struct spi_slave *slave, unsigned int bitlen,
 			dma = 0;
 	}
 
-	if (!dma || (len < MXSSSP_SMALL_TRANSFER)) {
-		writel(SSP_CTRL1_DMA_ENABLE, &ssp_regs->hw_ssp_ctrl1_clr);
-		return mxs_spi_xfer_pio(mxs_slave, data, len, write, flags);
-	} else {
-		writel(SSP_CTRL1_DMA_ENABLE, &ssp_regs->hw_ssp_ctrl1_set);
-		return mxs_spi_xfer_dma(mxs_slave, data, len, write, flags);
+	while (len) {
+		if (!dma || (len < MXSSSP_SMALL_TRANSFER)) {
+			tl = len;
+			writel(SSP_CTRL1_DMA_ENABLE, &regs->hw_ssp_ctrl1_clr);
+			ret = mxs_spi_xfer_pio(sslave, data, tl, write, flags);
+		} else {
+			/* 0x4000 bytes is the limit for DMA burst. */
+			tl = min(len, 0x4000);
+			writel(SSP_CTRL1_DMA_ENABLE, &regs->hw_ssp_ctrl1_set);
+			ret = mxs_spi_xfer_dma(sslave, data, tl, write, flags);
+		}
+
+		if (ret)
+			return ret;
+
+		data += tl;
+		len -= tl;
 	}
+
+	return ret;
 }
-- 
1.7.10.4