[PATCH v2 4/4] mmc: dw_mmc: correct the calculation for CLKDIV

[PATCH v2 4/4] mmc: dw_mmc: correct the calculation for CLKDIV

[Seungwon Jeon]

In case of "host->bus_hz < slot->clock", divider value is
miscalculated. And clock divider register value is multiple
of 2. If calculated divider value is odd number, result can
be over-clocking.

Signed-off-by: Seungwon Jeon <tgih.jun@samsung.com>
---
 drivers/mmc/host/dw_mmc.c |   10 ++++++----
 1 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index b070ee5..8f5768c 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -617,14 +617,16 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot)
 	u32 div;
 
 	if (slot->clock != host->current_speed) {
-		if (host->bus_hz % slot->clock)
+		div = host->bus_hz / slot->clock;
+		if (host->bus_hz % slot->clock &&
+			host->bus_hz > slot->clock)
 			/*
 			 * move the + 1 after the divide to prevent
 			 * over-clocking the card.
 			 */
-			div = ((host->bus_hz / slot->clock) >> 1) + 1;
-		else
-			div = (host->bus_hz  / slot->clock) >> 1;
+			div += 1;
+
+		div = (host->bus_hz != slot->clock) ? DIV_ROUND_UP(div, 2) : 0;
 
 		dev_info(&slot->mmc->class_dev,
 			 "Bus speed (slot %d) = %dHz (slot req %dHz, actual %dHZ"
-- 
1.7.0.4