From 3b9f7811595e796ec810b4459ea2711d9c6d2562 Mon Sep 17 00:00:00 2001
From: Anatolij Gustschin <agust@denx.de>
Date: Wed, 13 Mar 2013 14:57:43 +0100
Subject: spi/mpc512x-psc: optionally keep PSC SS asserted across xfer
 segmensts

commit 1ad849aee5f53353ed88d9cd3d68a51b03a7d44f upstream.

Some SPI slave devices require asserted chip select signal across
multiple transfer segments of an SPI message. Currently the driver
always de-asserts the internal SS signal for every single transfer
segment of the message and ignores the 'cs_change' flag of the
transfer description. Disable the internal chip select (SS) only
if this is needed and indicated by the 'cs_change' flag.

Without this change, each partial transfer of a surrounding
multi-part SPI transaction might erroneously change the SS
signal, which might prevent slaves from answering the request
that was sent in a previous transfer segment because the
transaction could be considered aborted (SS was de-asserted
before reading the response).

Reported-by: Gerhard Sittig <gerhard.sittig@ifm.com>
Signed-off-by: Anatolij Gustschin <agust@denx.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/spi/spi-mpc512x-psc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'drivers')

diff --git a/drivers/spi/spi-mpc512x-psc.c b/drivers/spi/spi-mpc512x-psc.c
index cb3a3106bd4..41e21bf4d45 100644
--- a/drivers/spi/spi-mpc512x-psc.c
+++ b/drivers/spi/spi-mpc512x-psc.c
@@ -164,7 +164,7 @@ static int mpc512x_psc_spi_transfer_rxtx(struct spi_device *spi,
 
 		for (i = count; i > 0; i--) {
 			data = tx_buf ? *tx_buf++ : 0;
-			if (len == EOFBYTE)
+			if (len == EOFBYTE && t->cs_change)
 				setbits32(&fifo->txcmd, MPC512x_PSC_FIFO_EOF);
 			out_8(&fifo->txdata_8, data);
 			len--;
-- 
cgit v1.2.3-18-g5258