openwrtv4/target/linux/brcm2708/patches-4.4/0252-clk-bcm2835-add-a-round-up-ability-to-the-clock-divi.patch

From 01993e1dda68d85ff6cf11cab6051bcefa46d2c1 Mon Sep 17 00:00:00 2001
From: Remi Pommarel <repk@triplefau.lt>
Date: Sun, 6 Dec 2015 17:22:46 +0100
Subject: [PATCH] clk: bcm2835: add a round up ability to the clock divisor

Make bcm2835_clock_choose_div to optionally round up the chosen MASH divisor
so that the resulting average rate will not be higher than the requested one.

Signed-off-by: Remi Pommarel <repk@triplefau.lt>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>
(cherry picked from commit 9c95b32ca09364e4687b72c4e17b78dc1c420026)
---
 drivers/clk/bcm/clk-bcm2835.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

--- a/drivers/clk/bcm/clk-bcm2835.c
+++ b/drivers/clk/bcm/clk-bcm2835.c
@@ -1164,22 +1164,24 @@ static int bcm2835_clock_is_on(struct cl
 
 static u32 bcm2835_clock_choose_div(struct clk_hw *hw,
 				    unsigned long rate,
-				    unsigned long parent_rate)
+				    unsigned long parent_rate,
+				    bool round_up)
 {
 	struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
 	const struct bcm2835_clock_data *data = clock->data;
-	u32 unused_frac_mask = GENMASK(CM_DIV_FRAC_BITS - data->frac_bits, 0);
+	u32 unused_frac_mask =
+		GENMASK(CM_DIV_FRAC_BITS - data->frac_bits, 0) >> 1;
 	u64 temp = (u64)parent_rate << CM_DIV_FRAC_BITS;
+	u64 rem;
 	u32 div;
 
-	do_div(temp, rate);
+	rem = do_div(temp, rate);
 	div = temp;
 
-	/* Round and mask off the unused bits */
-	if (unused_frac_mask != 0) {
-		div += unused_frac_mask >> 1;
-		div &= ~unused_frac_mask;
-	}
+	/* Round up and mask off the unused bits */
+	if (round_up && ((div & unused_frac_mask) != 0 || rem != 0))
+		div += unused_frac_mask + 1;
+	div &= ~unused_frac_mask;
 
 	/* clamp to min divider of 1 */
 	div = max_t(u32, div, 1 << CM_DIV_FRAC_BITS);
@@ -1219,7 +1221,7 @@ static long bcm2835_clock_round_rate(str
 				     unsigned long *parent_rate)
 {
 	struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
-	u32 div = bcm2835_clock_choose_div(hw, rate, *parent_rate);
+	u32 div = bcm2835_clock_choose_div(hw, rate, *parent_rate, false);
 
 	return bcm2835_clock_rate_from_divisor(clock, *parent_rate, div);
 }
@@ -1288,7 +1290,7 @@ static int bcm2835_clock_set_rate(struct
 	struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
 	struct bcm2835_cprman *cprman = clock->cprman;
 	const struct bcm2835_clock_data *data = clock->data;
-	u32 div = bcm2835_clock_choose_div(hw, rate, parent_rate);
+	u32 div = bcm2835_clock_choose_div(hw, rate, parent_rate, false);
 
 	cprman_write(cprman, data->div_reg, div);