mfd: cros_ec: spi: Calculate delay between transfers correctly

To avoid spamming the EC we calculate the time between the previous
transfer and the current transfer and force a delay if the time delta
is too small.

However, a small miscalculation causes the delay period to be
far too short. Most noticably this impacts commands with a long
turnaround time such as EC firmware reads and writes.

Signed-off-by: David Hendricks <dhendrix@chromium.org>
Signed-off-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Andrew Bresticker <abrestic@chromium.org>
Tested-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c
index 84af8d7a429544e7369daf66d2dbedb578cb12a1..c185eb67943fa4d77fc7aa788e9ddbee1d26ce35 100644 (file)
--- a/drivers/mfd/cros_ec_spi.c
+++ b/drivers/mfd/cros_ec_spi.c
@@ -219,7 +219,7 @@ static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev,
                ktime_get_ts(&ts);
                delay = timespec_to_ns(&ts) - ec_spi->last_transfer_ns;
                if (delay < EC_SPI_RECOVERY_TIME_NS)
-                       ndelay(delay);
+                       ndelay(EC_SPI_RECOVERY_TIME_NS - delay);
        }
 
        /* Transmit phase - send our message */