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author | Maxime COQUELIN <maxime.coquelin@st.com> | 2014-01-29 17:24:07 +0100 |
---|---|---|
committer | Mike Turquette <mturquette@linaro.org> | 2014-04-30 11:51:26 -0700 |
commit | 774b514390b1eb8476bc759262790762bd1ef45a (patch) | |
tree | b283823eca82e2e5a71fbd90b203da950fd96764 /drivers/clk | |
parent | 874f224cc52d64c912087e68e3724be95ad80ee7 (diff) | |
download | linux-stable-774b514390b1eb8476bc759262790762bd1ef45a.tar.gz linux-stable-774b514390b1eb8476bc759262790762bd1ef45a.tar.bz2 linux-stable-774b514390b1eb8476bc759262790762bd1ef45a.zip |
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>
Diffstat (limited to 'drivers/clk')
-rw-r--r-- | drivers/clk/clk-divider.c | 69 |
1 files changed, 67 insertions, 2 deletions
diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c index 4637697c139f..c57294563a98 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 = 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; |