[006/126] spi/mpc512x-psc: optionally keep PSC SS asserted across xfer segmensts

Steven Rostedt
2013-05-07T04:14:28Z

[-- Attachment #1: 0006-spi-mpc512x-psc-optionally-keep-PSC-SS-asserted-acro.patch --]
[-- Type: text/plain, Size: 1767 bytes --]

3.6.11.3 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Anatolij Gustschin <agust@denx.de>

[ Upstream commit 1ad849aee5f53353ed88d9cd3d68a51b03a7d44f ]

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>
Cc: stable@vger.kernel.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
drivers/spi/spi-mpc512x-psc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/spi/spi-mpc512x-psc.c b/drivers/spi/spi-mpc512x-psc.c
index 4c63f77..2e2b04f 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--;
--
1.7.10.4