mmc: atmel-mci: correct data timeout computation

commit 66292ad92c6d3f2f1c137a1c826b331ca8595dfd upstream.

The HSMCI operates at a rate of up to Master Clock divided by two.
Moreover previous calculation can cause overflows and so wrong
timeouts.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Chris Ball <cjb@laptop.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 8 insertions, 1 deletions

diff --git a/drivers/mmc/host/atmel-mci.c b/drivers/mmc/host/atmel-mci.c
index aa8039f473c..b6cd3867f72 100644
--- a/drivers/mmc/host/atmel-mci.c
+++ b/drivers/mmc/host/atmel-mci.c
@@ -468,7 +468,14 @@ err:
 static inline unsigned int ns_to_clocks(struct atmel_mci *host,
                                         unsigned int ns)
 {
-        return (ns * (host->bus_hz / 1000000) + 999) / 1000;
+        /*
+         * It is easier here to use us instead of ns for the timeout,
+         * it prevents from overflows during calculation.
+         */
+        unsigned int us = DIV_ROUND_UP(ns, 1000);
+
+        /* Maximum clock frequency is host->bus_hz/2 */
+        return us * (DIV_ROUND_UP(host->bus_hz, 2000000));
 }
 
 static void atmci_set_timeout(struct atmel_mci *host,