Re: [PATCH v2 5/6] pwm: mxs: avoid a division in mxs_pwm_apply()
From: Uwe Kleine-König <hidden>
Date: 2019-10-04 14:08:43
Also in:
linux-devicetree, linux-pwm, lkml
On Fri, Oct 04, 2019 at 03:32:06PM +0200, Rasmus Villemoes wrote:
Since the divisor is not a compile-time constant (unless gcc somehow decided to unroll the loop PERIOD_CDIV_MAX times), this does a somewhat expensive 32/32 division. Replace that with a right shift. We still have a 64/32 division just below, but at least in that case the divisor is compile-time constant. Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
quoted hunk ↗ jump to hunk
--- drivers/pwm/pwm-mxs.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)diff --git a/drivers/pwm/pwm-mxs.c b/drivers/pwm/pwm-mxs.c index 57562221c439..f2e57fcf8f8b 100644 --- a/drivers/pwm/pwm-mxs.c +++ b/drivers/pwm/pwm-mxs.c@@ -33,8 +33,8 @@ #define PERIOD_CDIV(div) (((div) & 0x7) << 20) #define PERIOD_CDIV_MAX 8 -static const unsigned int cdiv[PERIOD_CDIV_MAX] = { - 1, 2, 4, 8, 16, 64, 256, 1024 +static const u8 cdiv_shift[PERIOD_CDIV_MAX] = { + 0, 1, 2, 3, 4, 6, 8, 10
One small nitpick: I would like to see this name have a mxs_pwm_ prefix. But even without this change: Reviewed-by: Uwe Kleine-König <redacted> Thanks Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ | _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel