[PATCH v7 08/13] pwm: sifive: Use 64-bit division macros for period and duty cycle

From: Guru Das Srinagesh
Date: Mon Mar 09 2020 - 15:35:45 EST


Because period and duty cycle are defined in the PWM framework structs
as ints with units of nanoseconds, the maximum time duration that can be
set is limited to ~2.147 seconds. Redefining them as u64 values will
enable larger time durations to be set.

As a first step, prepare drivers to handle the switch to u64 period and
duty_cycle by replacing division operations involving pwm period and duty cycle
with their 64-bit equivalents as appropriate. The actual switch to u64 period
and duty_cycle follows as a separate patch.

Where the dividend is 64-bit but the divisor is 32-bit, use *_ULL
macros:
- DIV_ROUND_UP_ULL
- DIV_ROUND_CLOSEST_ULL
- div_u64

Where the divisor is 64-bit (dividend may be 32-bit or 64-bit), use
DIV64_* macros:
- DIV64_U64_ROUND_CLOSEST
- div64_u64

Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx>
Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx>
Cc: linux-riscv@xxxxxxxxxxxxxxxxxxx
Cc: Yash Shah <yash.shah@xxxxxxxxxx>
Cc: Atish Patra <atish.patra@xxxxxxx>

Signed-off-by: Guru Das Srinagesh <gurus@xxxxxxxxxxxxxx>
---
drivers/pwm/pwm-sifive.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
index cc63f9b..62de0bb 100644
--- a/drivers/pwm/pwm-sifive.c
+++ b/drivers/pwm/pwm-sifive.c
@@ -181,7 +181,7 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
* consecutively
*/
num = (u64)duty_cycle * (1U << PWM_SIFIVE_CMPWIDTH);
- frac = DIV_ROUND_CLOSEST_ULL(num, state->period);
+ frac = DIV64_U64_ROUND_CLOSEST(num, state->period);
/* The hardware cannot generate a 100% duty cycle */
frac = min(frac, (1U << PWM_SIFIVE_CMPWIDTH) - 1);

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