[PATCH 5/5] spi/dw_spi.c: conditional transfer mode changes

[George Shore <george-ofzTHo7+kyPpQY4QmZNtDQ@public.gmane.org>]

This allows the switching between transfer modes between 'transmit only',
'receive only' and 'transmit and receive' modes. Due to the design of the SPI
block, changing transfer modes requires that the block be disabled; in doing
so the chipselect line is inherently deasserted and (usually) the attached
device discards its state. Consequentially, switching modes requires that a
platform-specific chipselect function has been defined so that the chipselect
is not dropped during the change.

Signed-off-by: George Shore <george-ofzTHo7+kyPpQY4QmZNtDQ@public.gmane.org>
---
 drivers/spi/dw_spi.c |   16 ++++++++++++++++
 1 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/drivers/spi/dw_spi.c b/drivers/spi/dw_spi.c
index 4f91554..a1c195f 100644
--- a/drivers/spi/dw_spi.c
+++ b/drivers/spi/dw_spi.c
@@ -537,6 +537,22 @@ static void pump_transfers(unsigned long data)
 	}
 	message->state = RUNNING_STATE;
 
+	/*
+	 * Adjust transfer mode if necessary. Requires platform dependent
+	 * chipselect mechanism.
+	 */
+	if (dws->cs_control) {
+		if (dws->rx && dws->tx)
+			chip->tmode = 0x00;
+		else if (dws->rx)
+			chip->tmode = 0x02;
+		else
+			chip->tmode = 0x01;
+
+		cr0 &= ~(0x3 << SPI_MODE_OFFSET);
+		cr0 |= (chip->tmode << SPI_TMOD_OFFSET);
+	}
+
 	/* Check if current transfer is a DMA transaction */
 	dws->dma_mapped = map_dma_buffers(dws);
 
-- 
1.6.6.264.gd0743


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