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Message-Id: <1391012648-12481-3-git-send-email-maxime.coquelin@st.com>
Date: Wed, 29 Jan 2014 17:24:07 +0100
From: Maxime COQUELIN <maxime.coquelin@...com>
To: Mike Turquette <mturquette@...aro.org>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc: kernel@...inux.com, maxime.coquelin@...com
Subject: [PATCH 2/3] clk: divider: Add round to closest divider
In some cases, we want to be able to round the divider to the closest one,
instead than rounding up.
This patch adds a new CLK_DIVIDER_ROUND_CLOSEST flag to specify the divider
has to round to closest div, keeping rounding up as de default behaviour.
Signed-off-by: Maxime Coquelin <maxime.coquelin@...com>
---
drivers/clk/clk-divider.c | 69 ++++++++++++++++++++++++++++++++++++++++--
include/linux/clk-provider.h | 3 ++
2 files changed, 70 insertions(+), 2 deletions(-)
diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
index 2137d58..1eaa5d8 100644
--- a/drivers/clk/clk-divider.c
+++ b/drivers/clk/clk-divider.c
@@ -43,6 +43,17 @@ static unsigned int _get_table_maxdiv(const struct clk_div_table *table)
return maxdiv;
}
+static unsigned int _get_table_mindiv(const struct clk_div_table *table)
+{
+ unsigned int mindiv = UINT_MAX;
+ const struct clk_div_table *clkt;
+
+ for (clkt = table; clkt->div; clkt++)
+ if (clkt->div < mindiv)
+ mindiv = clkt->div;
+ return mindiv;
+}
+
static unsigned int _get_maxdiv(struct clk_divider *divider)
{
if (divider->flags & CLK_DIVIDER_ONE_BASED)
@@ -162,6 +173,24 @@ static int _round_up_table(const struct clk_div_table *table, int div)
return up;
}
+static int _round_down_table(const struct clk_div_table *table, int div)
+{
+ const struct clk_div_table *clkt;
+ int down = _get_table_mindiv(table);
+
+ for (clkt = table; clkt->div; clkt++) {
+ if (clkt->div == div)
+ return clkt->div;
+ else if (clkt->div > div)
+ continue;
+
+ if ((div - clkt->div) < (div - down))
+ down = clkt->div;
+ }
+
+ return down;
+}
+
static int _div_round_up(struct clk_divider *divider,
unsigned long parent_rate, unsigned long rate)
{
@@ -175,6 +204,42 @@ static int _div_round_up(struct clk_divider *divider,
return div;
}
+static int _div_round_closest(struct clk_divider *divider,
+ unsigned long parent_rate, unsigned long rate)
+{
+ int up, down, div;
+
+ up = down = div = DIV_ROUND_CLOSEST(parent_rate, rate);
+
+ if (divider->flags & CLK_DIVIDER_POWER_OF_TWO) {
+ up = __roundup_pow_of_two(div);
+ down = __rounddown_pow_of_two(div);
+ } else if (divider->table) {
+ up = _round_up_table(divider->table, div);
+ down = _round_down_table(divider->table, div);
+ }
+
+ return (up - div) <= (div - down) ? up : down;
+}
+
+static int _div_round(struct clk_divider *divider, unsigned long parent_rate,
+ unsigned long rate)
+{
+ if (divider->flags & CLK_DIVIDER_ROUND_CLOSEST)
+ return _div_round_closest(divider, parent_rate, rate);
+
+ return _div_round_up(divider, parent_rate, rate);
+}
+
+static bool _is_best_div(struct clk_divider *divider,
+ int rate, int now, int best)
+{
+ if (divider->flags & CLK_DIVIDER_ROUND_CLOSEST)
+ return abs(rate - now) < abs(rate - best);
+
+ return now <= rate && now > best;
+}
+
static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
unsigned long *best_parent_rate)
{
@@ -190,7 +255,7 @@ static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
if (!(__clk_get_flags(hw->clk) & CLK_SET_RATE_PARENT)) {
parent_rate = *best_parent_rate;
- bestdiv = _div_round_up(divider, parent_rate, rate);
+ bestdiv = _div_round(divider, parent_rate, rate);
bestdiv = bestdiv == 0 ? 1 : bestdiv;
bestdiv = bestdiv > maxdiv ? maxdiv : bestdiv;
return bestdiv;
@@ -217,7 +282,7 @@ static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
parent_rate = __clk_round_rate(__clk_get_parent(hw->clk),
MULT_ROUND_UP(rate, i));
now = parent_rate / i;
- if (now <= rate && now > best) {
+ if (_is_best_div(divider, rate, now, best)) {
bestdiv = i;
best = now;
*best_parent_rate = parent_rate;
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 7e59253..595f0ba 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -275,6 +275,8 @@ struct clk_div_table {
* of this register, and mask of divider bits are in higher 16-bit of this
* register. While setting the divider bits, higher 16-bit should also be
* updated to indicate changing divider bits.
+ * CLK_DIVIDER_ROUND_CLOSEST - Makes the best calculated divider to be rounded
+ * to the closest integer instead of the up one.
*/
struct clk_divider {
struct clk_hw hw;
@@ -290,6 +292,7 @@ struct clk_divider {
#define CLK_DIVIDER_POWER_OF_TWO BIT(1)
#define CLK_DIVIDER_ALLOW_ZERO BIT(2)
#define CLK_DIVIDER_HIWORD_MASK BIT(3)
+#define CLK_DIVIDER_ROUND_CLOSEST BIT(4)
extern const struct clk_ops clk_divider_ops;
struct clk *clk_register_divider(struct device *dev, const char *name,
--
1.7.9.5
--
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