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From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: "Thierry Reding" <thierry.reding@gmail.com>,
	"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
	"Lee Jones" <lee.jones@linaro.org>,
	"Daniel Thompson" <daniel.thompson@linaro.org>,
	"Jingoo Han" <jingoohan1@gmail.com>,
	"Bartlomiej Zolnierkiewicz" <b.zolnierkie@samsung.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	linux-pwm@vger.kernel.org, dri-devel@lists.freedesktop.org,
	linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2 2/4] backlight: pwm_bl: eliminate a 64/32 division
Date: Tue,  8 Oct 2019 14:03:25 +0200	[thread overview]
Message-ID: <20191008120327.24208-3-linux@rasmusvillemoes.dk> (raw)
In-Reply-To: <20191008120327.24208-1-linux@rasmusvillemoes.dk>

lightness*1000 is nowhere near overflowing 32 bits, so we can just use
an ordinary 32/32 division, which is much cheaper than the 64/32 done
via do_div().

Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
 drivers/video/backlight/pwm_bl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index cc44a02e95c7..672c5e7cfcd1 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -177,7 +177,7 @@ static u64 cie1931(unsigned int lightness, unsigned int scale)
 	 */
 	lightness *= 100;
 	if (lightness <= (8 * scale)) {
-		retval = DIV_ROUND_CLOSEST_ULL(lightness * 10, 9033);
+		retval = DIV_ROUND_CLOSEST(lightness * 10, 9033);
 	} else {
 		retval = int_pow((lightness + (16 * scale)) / 116, 3);
 		retval = DIV_ROUND_CLOSEST_ULL(retval, (scale * scale));
-- 
2.20.1


WARNING: multiple messages have this Message-ID (diff)
From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: "Thierry Reding" <thierry.reding@gmail.com>,
	"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
	"Lee Jones" <lee.jones@linaro.org>,
	"Daniel Thompson" <daniel.thompson@linaro.org>,
	"Jingoo Han" <jingoohan1@gmail.com>,
	"Bartlomiej Zolnierkiewicz" <b.zolnierkie@samsung.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	linux-pwm@vger.kernel.org, dri-devel@lists.freedesktop.org,
	linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2 2/4] backlight: pwm_bl: eliminate a 64/32 division
Date: Tue, 08 Oct 2019 12:03:25 +0000	[thread overview]
Message-ID: <20191008120327.24208-3-linux@rasmusvillemoes.dk> (raw)
In-Reply-To: <20191008120327.24208-1-linux@rasmusvillemoes.dk>

lightness*1000 is nowhere near overflowing 32 bits, so we can just use
an ordinary 32/32 division, which is much cheaper than the 64/32 done
via do_div().

Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
 drivers/video/backlight/pwm_bl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index cc44a02e95c7..672c5e7cfcd1 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -177,7 +177,7 @@ static u64 cie1931(unsigned int lightness, unsigned int scale)
 	 */
 	lightness *= 100;
 	if (lightness <= (8 * scale)) {
-		retval = DIV_ROUND_CLOSEST_ULL(lightness * 10, 9033);
+		retval = DIV_ROUND_CLOSEST(lightness * 10, 9033);
 	} else {
 		retval = int_pow((lightness + (16 * scale)) / 116, 3);
 		retval = DIV_ROUND_CLOSEST_ULL(retval, (scale * scale));
-- 
2.20.1

  parent reply	other threads:[~2019-10-08 12:05 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-08 12:03 [PATCH v2 0/4] backlight: pwm_bl: optimizations and small fix for cie1913 Rasmus Villemoes
2019-10-08 12:03 ` Rasmus Villemoes
2019-10-08 12:03 ` [PATCH v2 1/4] backlight: pwm_bl: fix cie1913 comments and constant Rasmus Villemoes
2019-10-08 12:03   ` Rasmus Villemoes
2019-10-14  7:27   ` Lee Jones
2019-10-14  7:27     ` Lee Jones
2019-10-23 20:21     ` Rasmus Villemoes
2019-10-23 20:21       ` Rasmus Villemoes
2019-10-23 20:21       ` Rasmus Villemoes
2019-10-08 12:03 ` Rasmus Villemoes [this message]
2019-10-08 12:03   ` [PATCH v2 2/4] backlight: pwm_bl: eliminate a 64/32 division Rasmus Villemoes
2019-10-14  7:27   ` Lee Jones
2019-10-14  7:27     ` Lee Jones
2019-10-08 12:03 ` [PATCH v2 3/4] backlight: pwm_bl: drop use of int_pow() Rasmus Villemoes
2019-10-08 12:03   ` Rasmus Villemoes
2019-10-14  7:27   ` Lee Jones
2019-10-14  7:27     ` Lee Jones
2019-10-08 12:03 ` [PATCH v2 4/4] backlight: pwm_bl: switch to power-of-2 base for fixed-point math Rasmus Villemoes
2019-10-08 12:03   ` Rasmus Villemoes
2019-10-14  7:27   ` Lee Jones
2019-10-14  7:27     ` Lee Jones

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