[PATCH] spi-fsl-spi: Align CS behaviour for last SPI msg

[Joakim Tjernlund]

According to spi.h cs_change can be used to leave the CS
active until next SPI transfer(paragraph ii).
Adjust driver to comply with (ii).

Signed-off-by: Joakim Tjernlund <joakim.tjernl...@infinera.com>
---
 drivers/spi/spi-fsl-spi.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/spi/spi-fsl-spi.c b/drivers/spi/spi-fsl-spi.c
index 061c1f38bf46..9a6cb26680a9 100644
--- a/drivers/spi/spi-fsl-spi.c
+++ b/drivers/spi/spi-fsl-spi.c
@@ -358,6 +358,7 @@ static int fsl_spi_do_one_msg(struct spi_master *master,
 {
        struct spi_device *spi = m->spi;
        struct spi_transfer *t, *first;
+       bool keep_cs = false;
        unsigned int cs_change;
        const int nsecs = 50;
        int status;
@@ -401,16 +402,21 @@ static int fsl_spi_do_one_msg(struct spi_master *master,
                        udelay(t->delay_usecs);
 
                if (cs_change) {
-                       ndelay(nsecs);
-                       fsl_spi_chipselect(spi, BITBANG_CS_INACTIVE);
-                       ndelay(nsecs);
+                       if (list_is_last(&t->transfer_list,
+                                        &m->transfers)) {
+                               keep_cs = true;
+                       } else {
+                               ndelay(nsecs);
+                               fsl_spi_chipselect(spi, BITBANG_CS_INACTIVE);
+                               ndelay(nsecs);
+                       }
                }
        }
 
        m->status = status;
        spi_finalize_current_message(master);
 
-       if (status || !cs_change) {
+       if (status || !keep_cs) {
                ndelay(nsecs);
                fsl_spi_chipselect(spi, BITBANG_CS_INACTIVE);
        }
-- 
2.13.0