[PATCH/RFC,2/2] clk: renesas: r8a7795: Do rounding for calculated frequency value

Commit Message

Yoshihiro Kaneko Aug. 7, 2016, 5:58 p.m. UTC

From: Dien Pham <[e-mail]>

The calculation value has some errors after some calculation,
especially, when one of the input value is odd value.
This patch applies rounding to closest frequency at 100Mhz unit.

Signed-off-by: Dien Pham <[e-mail]>
Signed-off-by: Takeshi Kihara <[e-mail]>
Signed-off-by: Yoshihiro Kaneko <[e-mail]>
---
 drivers/clk/renesas/clk-rcar-gen2.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

Patch

diff --git a/drivers/clk/renesas/clk-rcar-gen2.c b/drivers/clk/renesas/clk-rcar-gen2.c
index 7519f71..5c4dcc7 100644
--- a/drivers/clk/renesas/clk-rcar-gen2.c
+++ b/drivers/clk/renesas/clk-rcar-gen2.c
@@ -60,13 +60,16 @@  static unsigned long cpg_z_clk_recalc_rate(struct clk_hw *hw,
 	struct cpg_z_clk *zclk = to_z_clk(hw);
 	unsigned int mult;
 	unsigned int val;
+	unsigned long rate;
 
 	val = (clk_readl(zclk->reg) & CPG_FRQCRC_ZFC_MASK)
 	    >> CPG_FRQCRC_ZFC_SHIFT;
 	mult = 32 - val;
 
-	/* Add 1/2 to reduce the math error that raises by math rounding */
-	return div_u64((u64)parent_rate * mult + 16, 32);
+	rate = div_u64((u64)parent_rate * mult + 16, 32);
+	/* Round to closest value at 100MHz unit */
+	rate = 100000000 * DIV_ROUND_CLOSEST(rate, 100000000);
+	return rate;
 }
 
 static long cpg_z_clk_round_rate(struct clk_hw *hw, unsigned long rate,