spi: Fix handling of cs_change in core implementation

The core implementation of cs_change didn't follow the documentation
which says that cs_change in the middle of the transfer means to briefly
deassert chip select, instead it followed buggy drivers which change the
polarity of chip select.  Use a delay of 10us between deassert and
reassert simply from pulling numbers out of a hat.

Reported-by: Gerhard Sittig <gsi@denx.de>
Signed-off-by: Mark Brown <broonie@linaro.org>

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 23756b0..5d826f0 100644 (file)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -591,7 +591,6 @@ static int spi_transfer_one_message(struct spi_master *master,
                                    struct spi_message *msg)
 {
        struct spi_transfer *xfer;
-       bool cur_cs = true;
        bool keep_cs = false;
        int ret = 0;
 
@@ -627,8 +626,9 @@ static int spi_transfer_one_message(struct spi_master *master,
                                         &msg->transfers)) {
                                keep_cs = true;
                        } else {
-                               cur_cs = !cur_cs;
-                               spi_set_cs(msg->spi, cur_cs);
+                               spi_set_cs(msg->spi, false);
+                               udelay(10);
+                               spi_set_cs(msg->spi, true);
                        }
                }