commit: 1ad849aee5f53353ed88d9cd3d68a51b03a7d44f
From: Anatolij Gustschin <agust@xxxxxxx>
Date: Wed, 13 Mar 2013 14:57:43 +0100
Subject: spi/mpc512x-psc: optionally keep PSC SS asserted across xfer
segmensts
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@xxxxxxx>
Signed-off-by: Anatolij Gustschin <agust@xxxxxxx>
Signed-off-by: Mark Brown <broonie@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
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 89480b2..3e490ee 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
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