Introduce a new API function to round a rate to the closest possible rate the HW clock can generate. In contrast to 'clk_round_rate()' which works similar, but always returns a frequency <= its input rate. The code comes from Uwe and was copied from this LKML thread: https://lkml.org/lkml/2013/3/21/115 Signed-off-by: Soren Brinkmann <soren.brinkmann@xxxxxxxxxx> --- drivers/clk/clk.c | 26 ++++++++++++++++++++++++-- include/linux/clk.h | 14 ++++++++++++-- 2 files changed, 36 insertions(+), 4 deletions(-) diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index dff0373f53c1..b715f5a9826c 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -1011,8 +1011,9 @@ unsigned long __clk_round_rate(struct clk *clk, unsigned long rate) * @rate: the rate which is to be rounded * * Takes in a rate as input and rounds it to a rate that the clk can actually - * use which is then returned. If clk doesn't support round_rate operation - * then the parent rate is returned. + * use and does not exceed the requested frequency, which is then returned. + * If clk doesn't support round_rate operation then the parent rate + * is returned. */ long clk_round_rate(struct clk *clk, unsigned long rate) { @@ -1027,6 +1028,27 @@ long clk_round_rate(struct clk *clk, unsigned long rate) EXPORT_SYMBOL_GPL(clk_round_rate); /** + * clk_round_rate_nearest - round the given rate for a clk + * @clk: the clk for which we are rounding a rate + * @rate: the rate which is to be rounded + * + * Takes in a rate as input and rounds it to the closest rate that the clk + * can actually use which is then returned. If clk doesn't support + * round_rate operation then the parent rate is returned. + */ +long clk_round_rate_nearest(struct clk *clk, unsigned long rate) +{ + long lower_limit = clk_round_rate(clk, rate); + long upper_limit = clk_round_rate(clk, rate + (rate - lower_limit)); + + if (rate - lower_limit < upper_limit - rate) + return lower_limit; + else + return upper_limit; +} +EXPORT_SYMBOL_GPL(clk_round_rate_nearest); + +/** * __clk_notify - call clk notifier chain * @clk: struct clk * that is changing rate * @msg: clk notifier type (see include/linux/clk.h) diff --git a/include/linux/clk.h b/include/linux/clk.h index fb5e097d8f72..2f83bf030ac6 100644 --- a/include/linux/clk.h +++ b/include/linux/clk.h @@ -255,15 +255,25 @@ void devm_clk_put(struct device *dev, struct clk *clk); /** - * clk_round_rate - adjust a rate to the exact rate a clock can provide + * clk_round_rate - round a rate to the exact rate a clock can provide not + * exceeding @rate * @clk: clock source * @rate: desired clock rate in Hz * - * Returns rounded clock rate in Hz, or negative errno. + * Returns rounded clock rate in Hz, or parent rate */ long clk_round_rate(struct clk *clk, unsigned long rate); /** + * clk_round_rate_nearest - round a rate to the exact rate a clock can provide + * @clk: the clk for which we are rounding a rate + * @rate: the rate which is to be rounded + * + * Returns rounded clock rate in Hz, or parent rate + */ +long clk_round_rate_nearest(struct clk *clk, unsigned long rate); + +/** * clk_set_rate - set the clock rate for a clock source * @clk: clock source * @rate: desired clock rate in Hz -- 1.9.3.1.ga73a6ad -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
