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>
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@ -43,6 +43,17 @@ static unsigned int _get_table_maxdiv(const struct clk_div_table *table)
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return maxdiv;
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}
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static unsigned int _get_table_mindiv(const struct clk_div_table *table)
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{
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unsigned int mindiv = UINT_MAX;
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const struct clk_div_table *clkt;
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for (clkt = table; clkt->div; clkt++)
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if (clkt->div < mindiv)
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mindiv = clkt->div;
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return mindiv;
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}
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static unsigned int _get_maxdiv(struct clk_divider *divider)
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{
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if (divider->flags & CLK_DIVIDER_ONE_BASED)
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@ -162,6 +173,24 @@ static int _round_up_table(const struct clk_div_table *table, int div)
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return up;
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}
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static int _round_down_table(const struct clk_div_table *table, int div)
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{
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const struct clk_div_table *clkt;
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int down = _get_table_mindiv(table);
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for (clkt = table; clkt->div; clkt++) {
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if (clkt->div == div)
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return clkt->div;
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else if (clkt->div > div)
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continue;
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if ((div - clkt->div) < (div - down))
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down = clkt->div;
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}
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return down;
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}
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static int _div_round_up(struct clk_divider *divider,
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unsigned long parent_rate, unsigned long rate)
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{
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@ -175,6 +204,42 @@ static int _div_round_up(struct clk_divider *divider,
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return div;
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}
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static int _div_round_closest(struct clk_divider *divider,
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unsigned long parent_rate, unsigned long rate)
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{
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int up, down, div;
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up = down = div = DIV_ROUND_CLOSEST(parent_rate, rate);
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if (divider->flags & CLK_DIVIDER_POWER_OF_TWO) {
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up = __roundup_pow_of_two(div);
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down = __rounddown_pow_of_two(div);
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} else if (divider->table) {
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up = _round_up_table(divider->table, div);
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down = _round_down_table(divider->table, div);
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}
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return (up - div) <= (div - down) ? up : down;
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}
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static int _div_round(struct clk_divider *divider, unsigned long parent_rate,
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unsigned long rate)
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{
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if (divider->flags & CLK_DIVIDER_ROUND_CLOSEST)
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return _div_round_closest(divider, parent_rate, rate);
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return _div_round_up(divider, parent_rate, rate);
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}
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static bool _is_best_div(struct clk_divider *divider,
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int rate, int now, int best)
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{
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if (divider->flags & CLK_DIVIDER_ROUND_CLOSEST)
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return abs(rate - now) < abs(rate - best);
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return now <= rate && now > best;
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}
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static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
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unsigned long *best_parent_rate)
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{
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@ -190,7 +255,7 @@ static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
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if (!(__clk_get_flags(hw->clk) & CLK_SET_RATE_PARENT)) {
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parent_rate = *best_parent_rate;
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bestdiv = _div_round_up(divider, parent_rate, rate);
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bestdiv = _div_round(divider, parent_rate, rate);
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bestdiv = bestdiv == 0 ? 1 : bestdiv;
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bestdiv = bestdiv > maxdiv ? maxdiv : bestdiv;
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return bestdiv;
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@ -217,7 +282,7 @@ static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
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parent_rate = __clk_round_rate(__clk_get_parent(hw->clk),
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MULT_ROUND_UP(rate, i));
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now = DIV_ROUND_UP(parent_rate, i);
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if (now <= rate && now > best) {
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if (_is_best_div(divider, rate, now, best)) {
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bestdiv = i;
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best = now;
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*best_parent_rate = parent_rate;
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@ -312,6 +312,8 @@ struct clk_div_table {
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* of this register, and mask of divider bits are in higher 16-bit of this
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* register. While setting the divider bits, higher 16-bit should also be
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* updated to indicate changing divider bits.
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* CLK_DIVIDER_ROUND_CLOSEST - Makes the best calculated divider to be rounded
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* to the closest integer instead of the up one.
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*/
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struct clk_divider {
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struct clk_hw hw;
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@ -327,6 +329,7 @@ struct clk_divider {
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#define CLK_DIVIDER_POWER_OF_TWO BIT(1)
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#define CLK_DIVIDER_ALLOW_ZERO BIT(2)
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#define CLK_DIVIDER_HIWORD_MASK BIT(3)
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#define CLK_DIVIDER_ROUND_CLOSEST BIT(4)
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extern const struct clk_ops clk_divider_ops;
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struct clk *clk_register_divider(struct device *dev, const char *name,
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