[patch 2.6.28-rc6] spi: mpc52xx_psc_spi chipselect bugfix

[patch 2.6.28-rc6] spi: mpc52xx_psc_spi chipselect bugfix

[David Brownell]

From: Stefano Babic <sbabic-ynQEQJNshbs@public.gmane.org>

According to the manual the "tdfOnExit" flag must be set on the last byte
we want to send. The PSC controller holds SS low until the flag is set.

However, the flag was set always on the last byte of the FIFO, independently if
it is the last byte of the transfer. This generates spurious toggling of the
SS signals that breaks the protocol of some peripherals.  Fix.

Signed-off-by: Stefano Babic <sbabic-ynQEQJNshbs@public.gmane.org>
Acked-by: Grant Likely <grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org>
Signed-off-by: David Brownell <dbrownell-Rn4VEauK+AKRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>
---
 drivers/spi/mpc52xx_psc_spi.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/spi/mpc52xx_psc_spi.c
+++ b/drivers/spi/mpc52xx_psc_spi.c
@@ -142,6 +142,7 @@ static int mpc52xx_psc_spi_transfer_rxtx
 	unsigned rfalarm;
 	unsigned send_at_once = MPC52xx_PSC_BUFSIZE;
 	unsigned recv_at_once;
+	int last_block = 0;
 
 	if (!t->tx_buf && !t->rx_buf && t->len)
 		return -EINVAL;
@@ -151,15 +152,17 @@ static int mpc52xx_psc_spi_transfer_rxtx
 	while (rb < t->len) {
 		if (t->len - rb > MPC52xx_PSC_BUFSIZE) {
 			rfalarm = MPC52xx_PSC_RFALARM;
+			last_block = 0;
 		} else {
 			send_at_once = t->len - sb;
 			rfalarm = MPC52xx_PSC_BUFSIZE - (t->len - rb);
+			last_block = 1;
 		}
 
 		dev_dbg(&spi->dev, "send %d bytes...\n", send_at_once);
 		for (; send_at_once; sb++, send_at_once--) {
 			/* set EOF flag before the last word is sent */
-			if (send_at_once == 1)
+			if (send_at_once == 1 && last_block)
 				out_8(&psc->ircr2, 0x01);
 
 			if (tx_buf)

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