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Message-ID: <20140424153742.23156.29975@quantum>
Date: Thu, 24 Apr 2014 08:37:42 -0700
From: Mike Turquette <mturquette@...aro.org>
To: Maxime COQUELIN <maxime.coquelin@...com>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc: kernel@...inux.com, maxime.coquelin@...com
Subject: Re: [PATCH 2/3] clk: divider: Add round to closest divider
Quoting Maxime COQUELIN (2014-01-29 08:24:07)
> 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.
I've taken patch #2 and #3 into clk-next for 3.16.
Thanks!
Mike
>
> 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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