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Commit 774b5143 authored by Maxime COQUELIN's avatar Maxime COQUELIN Committed by Mike Turquette
Browse files

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: default avatarMaxime Coquelin <maxime.coquelin@st.com>
Signed-off-by: default avatarMike Turquette <mturquette@linaro.org>
parent 874f224c

drivers/clk/clk-divider.c

+67 −2
Original line number Diff line number Diff line
@@ -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;

include/linux/clk-provider.h

+3 −0
Original line number Diff line number Diff line
@@ -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,