[PATCH/RFC,1/2] clk: renesas: r8a7795: Improve the calculated value of Clock.

Commit Message

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

From: Dien Pham <[e-mail]>

This patch improves the calculated value of Z Clock when odd frequency
(as 33.33 MHz) is inputted.

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, 4 insertions(+), 3 deletions(-)

Patch

diff --git a/drivers/clk/renesas/clk-rcar-gen2.c b/drivers/clk/renesas/clk-rcar-gen2.c
index 00e6aba..7519f71 100644
--- a/drivers/clk/renesas/clk-rcar-gen2.c
+++ b/drivers/clk/renesas/clk-rcar-gen2.c
@@ -65,7 +65,8 @@  static unsigned long cpg_z_clk_recalc_rate(struct clk_hw *hw,
 	    >> CPG_FRQCRC_ZFC_SHIFT;
 	mult = 32 - val;
 
-	return div_u64((u64)parent_rate * mult, 32);
+	/* Add 1/2 to reduce the math error that raises by math rounding */
+	return div_u64((u64)parent_rate * mult + 16, 32);
 }
 
 static long cpg_z_clk_round_rate(struct clk_hw *hw, unsigned long rate,
@@ -77,7 +78,7 @@  static long cpg_z_clk_round_rate(struct clk_hw *hw, unsigned long rate,
 	if (!prate)
 		prate = 1;
 
-	mult = div_u64((u64)rate * 32, prate);
+	mult = div_u64((u64)rate * 32 + prate / 2, prate);
 	mult = clamp(mult, 1U, 32U);
 
 	return *parent_rate / 32 * mult;
@@ -91,7 +92,7 @@  static int cpg_z_clk_set_rate(struct clk_hw *hw, unsigned long rate,
 	u32 val, kick;
 	unsigned int i;
 
-	mult = div_u64((u64)rate * 32, parent_rate);
+	mult = div_u64((u64)rate * 32 + parent_rate / 2, parent_rate);
 	mult = clamp(mult, 1U, 32U);
 
 	if (clk_readl(zclk->kick_reg) & CPG_FRQCRB_KICK)