[PATCH v2] spi: fix the divide by 0 error when calculating xfer waiting time

[Xu Yilun]

The xfer waiting time is the result of xfer->len / xfer->speed_hz. This
patch makes the assumption of 1khz xfer speed if the xfer->speed_hz is
not assigned and stays 0. This avoids the divide by 0 issue and ensures
a reasonable tolerant waiting time.

Signed-off-by: Xu Yilun <yilun...@intel.com>
---
v2: use the normal conditional statement instead of the ternery operator
    change the default xfer speed from 1khz to 100khz
---
 drivers/spi/spi.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 51d7c00..aacae88 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1108,6 +1108,7 @@ static int spi_transfer_wait(struct spi_controller *ctlr,
 {
        struct spi_statistics *statm = &ctlr->statistics;
        struct spi_statistics *stats = &msg->spi->statistics;
+       u32 speed_hz = xfer->speed_hz;
        unsigned long long ms;
 
        if (spi_controller_is_slave(ctlr)) {
@@ -1116,8 +1117,11 @@ static int spi_transfer_wait(struct spi_controller *ctlr,
                        return -EINTR;
                }
        } else {
+               if (!speed_hz)
+                       speed_hz = 100000;
+
                ms = 8LL * 1000LL * xfer->len;
-               do_div(ms, xfer->speed_hz);
+               do_div(ms, speed_hz);
                ms += ms + 200; /* some tolerance */
 
                if (ms > UINT_MAX)
-- 
2.7.4