From 052dc7c45d8f685fb3720a08331ba3e91e87937e Mon Sep 17 00:00:00 2001
From: George Shore <george@georgeshore.com>
Date: Thu, 21 Jan 2010 11:40:52 +0000
Subject: [PATCH] spi/dw_spi: conditional transfer mode changes

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@georgeshore.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
---
 drivers/spi/dw_spi.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/spi/dw_spi.c b/drivers/spi/dw_spi.c
index 3853df5db052..e434320fded8 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);