[ 27/42] mmc: atmel-mci: correct data timeout computation
From: Greg KH
Date: Wed Apr 11 2012 - 19:33:58 EST
3.0-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ludovic Desroches <ludovic.desroches@xxxxxxxxx>
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@xxxxxxxxx>
Acked-by: Nicolas Ferre <nicolas.ferre@xxxxxxxxx>
Signed-off-by: Chris Ball <cjb@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/mmc/host/atmel-mci.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
--- 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,
--
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