From 57c5c28dbc835c67a9c23912bab56b7f165e7715 Mon Sep 17 00:00:00 2001
From: Eero Nurkkala <ext-eero.nurkkala@nokia.com>
Date: Wed, 29 Jul 2009 15:02:12 -0700
Subject: [PATCH] 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>
---
drivers/spi/omap2_mcspi.c | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)
diff --git a/drivers/spi/omap2_mcspi.c b/drivers/spi/omap2_mcspi.c
index 2b64091b0f1f..9b80ad36dbba 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;
}
--
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