spi/davinci: Support DMA transfers larger than 65535 words

The current davinci SPI driver, in DMA mode, is limited to 65535
words for a single transfer.  Modify the driver by configuring a
3 dimensional EDMA transfer to support up to 65535x65535
words.

Signed-off-by: Michael Williamson <michael.williamson@criticallink.com>
Tested-by: Stefano Babic <sbabic@denx.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

1 files changed, 25 insertions, 8 deletions

diff --git a/drivers/spi/davinci_spi.c b/drivers/spi/davinci_spi.c
index 68ed377cc626..e90c2d6a84b3 100644
--- a/drivers/spi/davinci_spi.c
+++ b/drivers/spi/davinci_spi.c
@@ -571,6 +571,7 @@ static int davinci_spi_bufs(struct spi_device *spi, struct spi_transfer *t)
                 unsigned long tx_reg, rx_reg;
                 struct edmacc_param param;
                 void *rx_buf;
+                int b, c;
 
                 dma = &dspi->dma;
 
@@ -599,14 +600,30 @@ static int davinci_spi_bufs(struct spi_device *spi, struct spi_transfer *t)
                         }
                 }
 
+                /*
+                 * If number of words is greater than 65535, then we need
+                 * to configure a 3 dimension transfer.  Use the BCNTRLD
+                 * feature to allow for transfers that aren't even multiples
+                 * of 65535 (or any other possible b size) by first transferring
+                 * the remainder amount then grabbing the next N blocks of
+                 * 65535 words.
+                 */
+
+                c = dspi->wcount / (SZ_64K - 1);        /* N 65535 Blocks */
+                b = dspi->wcount - c * (SZ_64K - 1);    /* Remainder */
+                if (b)
+                        c++;
+                else
+                        b = SZ_64K - 1;
+
                 param.opt = TCINTEN | EDMA_TCC(dma->tx_channel);
                 param.src = t->tx_buf ? t->tx_dma : tx_reg;
-                param.a_b_cnt = dspi->wcount << 16 | data_type;
+                param.a_b_cnt = b << 16 | data_type;
                 param.dst = tx_reg;
                 param.src_dst_bidx = t->tx_buf ? data_type : 0;
-                param.link_bcntrld = 0xffff;
-                param.src_dst_cidx = 0;
-                param.ccnt = 1;
+                param.link_bcntrld = 0xffffffff;
+                param.src_dst_cidx = t->tx_buf ? data_type : 0;
+                param.ccnt = c;
                 edma_write_slot(dma->tx_channel, &param);
                 edma_link(dma->tx_channel, dma->dummy_param_slot);
 
@@ -643,12 +660,12 @@ static int davinci_spi_bufs(struct spi_device *spi, struct spi_transfer *t)
 
                 param.opt = TCINTEN | EDMA_TCC(dma->rx_channel);
                 param.src = rx_reg;
-                param.a_b_cnt = dspi->rcount << 16 | data_type;
+                param.a_b_cnt = b << 16 | data_type;
                 param.dst = t->rx_dma;
                 param.src_dst_bidx = (t->rx_buf ? data_type : 0) << 16;
-                param.link_bcntrld = 0xffff;
-                param.src_dst_cidx = 0;
-                param.ccnt = 1;
+                param.link_bcntrld = 0xffffffff;
+                param.src_dst_cidx = (t->rx_buf ? data_type : 0) << 16;
+                param.ccnt = c;
                 edma_write_slot(dma->rx_channel, &param);
 
                 if (pdata->cshold_bug)