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authorEero Nurkkala <ext-eero.nurkkala@nokia.com>2009-07-29 15:02:12 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-07-29 19:10:35 -0700
commit57c5c28dbc835c67a9c23912bab56b7f165e7715 (patch)
tree6d3ddbbff6aa875b00f52fb7efc792faf51b9ae2 /drivers/spi
parentddb22195cb3dc5175ba3aac5e957d0e34cd2ee73 (diff)
spi: omap2_mcspi rxdma bugfix
When data is read through DMA, the last element must be read separately through the RX register. It cannot be transferred by the DMA. For further details see e.g. OMAP35x TRM (table 19-16). Without the fix the driver causes extra clocks to be clocked to the bus after DMA RX operations. This can cause interesting behaviour with some devices. Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com> Signed-off-by: Eero Nurkkala <ext-eero.nurkkala@nokia.com> [aaro.koskinen@nokia.com: Simplified the patch while keeping the idea.] Signed-off-by: Aaro Koskinen <aaro.koskinen@nokia.com> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/spi')
-rw-r--r--drivers/spi/omap2_mcspi.c21
1 files changed, 20 insertions, 1 deletions
diff --git a/drivers/spi/omap2_mcspi.c b/drivers/spi/omap2_mcspi.c
index 2b64091b0f1..9b80ad36dbb 100644
--- a/drivers/spi/omap2_mcspi.c
+++ b/drivers/spi/omap2_mcspi.c
@@ -272,7 +272,7 @@ omap2_mcspi_txrx_dma(struct spi_device *spi, struct spi_transfer *xfer)
if (rx != NULL) {
omap_set_dma_transfer_params(mcspi_dma->dma_rx_channel,
- data_type, element_count, 1,
+ data_type, element_count - 1, 1,
OMAP_DMA_SYNC_ELEMENT,
mcspi_dma->dma_rx_sync_dev, 1);
@@ -303,6 +303,25 @@ omap2_mcspi_txrx_dma(struct spi_device *spi, struct spi_transfer *xfer)
if (rx != NULL) {
wait_for_completion(&mcspi_dma->dma_rx_completion);
dma_unmap_single(NULL, xfer->rx_dma, count, DMA_FROM_DEVICE);
+ omap2_mcspi_set_enable(spi, 0);
+ if (likely(mcspi_read_cs_reg(spi, OMAP2_MCSPI_CHSTAT0)
+ & OMAP2_MCSPI_CHSTAT_RXS)) {
+ u32 w;
+
+ w = mcspi_read_cs_reg(spi, OMAP2_MCSPI_RX0);
+ if (word_len <= 8)
+ ((u8 *)xfer->rx_buf)[element_count - 1] = w;
+ else if (word_len <= 16)
+ ((u16 *)xfer->rx_buf)[element_count - 1] = w;
+ else /* word_len <= 32 */
+ ((u32 *)xfer->rx_buf)[element_count - 1] = w;
+ } else {
+ dev_err(&spi->dev, "DMA RX last word empty");
+ count -= (word_len <= 8) ? 1 :
+ (word_len <= 16) ? 2 :
+ /* word_len <= 32 */ 4;
+ }
+ omap2_mcspi_set_enable(spi, 1);
}
return count;
}