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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@st.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
hifive-unleashed-5.1
Maxime COQUELIN 2014-01-29 17:24:07 +01:00 committed by Mike Turquette
parent 874f224cc5
commit 774b514390
2 changed files with 70 additions and 2 deletions
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69
drivers/clk/clk-divider.c
View File

@ -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 = DIV_ROUND_UP(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;

3
include/linux/clk-provider.h
View File

@ -312,6 +312,8 @@ 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;
@ -327,6 +329,7 @@ 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,