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| author | Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com> | 2019-01-09 17:19:08 +0900 |
|---|---|---|
| committer | Thierry Reding <thierry.reding@gmail.com> | 2019-03-04 12:14:21 +0100 |
| commit | b4f9a7268dbe9d55a6bc8c3123cb518657743b76 (patch) | |
| tree | 57314d875a9aff683bac92357e6b6dfe4dbd121c | |
| parent | 8cc2b970397c59b25ffb22e0e4a86753fa162619 (diff) | |
| download | linux-b4f9a7268dbe9d55a6bc8c3123cb518657743b76.tar.gz linux-b4f9a7268dbe9d55a6bc8c3123cb518657743b76.tar.bz2 linux-b4f9a7268dbe9d55a6bc8c3123cb518657743b76.zip | |
pwm: rcar: Improve calculation of divider
The rcar_pwm_get_clock_division() has a loop to calculate the divider,
but the value of div should be calculatable without a loop. So, this
patch improves it.
This algorithm is suggested by Uwe Kleine-König and Laurent Pinchart.
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
| -rw-r--r-- | drivers/pwm/pwm-rcar.c | 16 |
1 files changed, 7 insertions, 9 deletions
diff --git a/drivers/pwm/pwm-rcar.c b/drivers/pwm/pwm-rcar.c index 1e13fbb41fd1..cfe7dd1b448e 100644 --- a/drivers/pwm/pwm-rcar.c +++ b/drivers/pwm/pwm-rcar.c @@ -8,6 +8,8 @@ #include <linux/clk.h> #include <linux/err.h> #include <linux/io.h> +#include <linux/log2.h> +#include <linux/math64.h> #include <linux/module.h> #include <linux/of.h> #include <linux/platform_device.h> @@ -68,19 +70,15 @@ static void rcar_pwm_update(struct rcar_pwm_chip *rp, u32 mask, u32 data, static int rcar_pwm_get_clock_division(struct rcar_pwm_chip *rp, int period_ns) { unsigned long clk_rate = clk_get_rate(rp->clk); - unsigned long long max; /* max cycle / nanoseconds */ - unsigned int div; + u64 div, tmp; if (clk_rate == 0) return -EINVAL; - for (div = 0; div <= RCAR_PWM_MAX_DIVISION; div++) { - max = (unsigned long long)NSEC_PER_SEC * RCAR_PWM_MAX_CYCLE * - (1 << div); - do_div(max, clk_rate); - if (period_ns <= max) - break; - } + div = (u64)NSEC_PER_SEC * RCAR_PWM_MAX_CYCLE; + tmp = (u64)period_ns * clk_rate + div - 1; + tmp = div64_u64(tmp, div); + div = ilog2(tmp - 1) + 1; return (div <= RCAR_PWM_MAX_DIVISION) ? div : -ERANGE; } |