clk: vt8500: Fix device clock divisor calculations

When calculating device clock divisor values in set_rate and
round_rate, we do a simple integer divide. If parent_rate / rate
has a fraction, this is dropped which results in the device clock
being set too high.

This patch corrects the problem by adding 1 to the calculated
divisor if the division would have had a decimal result.

Signed-off-by: Tony Prisk <linux@prisktech.co.nz>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/drivers/clk/clk-vt8500.c b/drivers/clk/clk-vt8500.c
index 0cb26be..3306c2b 100644
--- a/drivers/clk/clk-vt8500.c
+++ b/drivers/clk/clk-vt8500.c
@@ -123,6 +123,10 @@ static long vt8500_dclk_round_rate(struct clk_hw *hw, unsigned long rate,
 	struct clk_device *cdev = to_clk_device(hw);
 	u32 divisor = *prate / rate;
 
+	/* If prate / rate would be decimal, incr the divisor */
+	if (rate * divisor < *prate)
+		divisor++;
+
 	/*
 	 * If this is a request for SDMMC we have to adjust the divisor
 	 * when >31 to use the fixed predivisor
@@ -141,6 +145,10 @@ static int vt8500_dclk_set_rate(struct clk_hw *hw, unsigned long rate,
 	u32 divisor = parent_rate / rate;
 	unsigned long flags = 0;
 
+	/* If prate / rate would be decimal, incr the divisor */
+	if (rate * divisor < *prate)
+		divisor++;
+
 	if (divisor == cdev->div_mask + 1)
 		divisor = 0;