linux-kernel - [RESEND PATCH v5 1/5] pwm-backlight: enable/disable the PWM before/after LCD enable toggle.

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Date:   Fri, 16 Feb 2018 18:40:30 +0100
From:   Enric Balletbo i Serra <enric.balletbo@...labora.com>
To:     Lee Jones <lee.jones@...aro.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Rob Herring <robh+dt@...nel.org>, Pavel Machek <pavel@....cz>,
        Heiko Stuebner <heiko@...ech.de>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Richard Purdie <rpurdie@...ys.net>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        linux-pwm@...r.kernel.org, linux-fbdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, groeck@...omium.org,
        linux-rockchip@...ts.infradead.org, kernel@...labora.com
Subject: [RESEND PATCH v5 1/5] pwm-backlight: enable/disable the PWM before/after LCD enable toggle.

Before this patch the enable signal was set before the PWM signal and
vice-versa on power off. This sequence is wrong, at least, it is on
the different panels datasheets that I checked, so I inverted the sequence
to follow the specs.

For reference the following panels have the mentioned sequence:
  - N133HSE-EA1 (Innolux)
  - N116BGE (Innolux)
  - N156BGE-L21 (Innolux)
  - B101EAN0 (Auo)
  - B101AW03 (Auo)
  - LTN101NT05 (Samsung)
  - CLAA101WA01A (Chunghwa)

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
Acked-by: Daniel Thompson <daniel.thompson@...aro.org>
Acked-by: Jingoo Han <jingoohan1@...il.com>
---
Changes since v4:
 - Rebase on top of mainline.
 - Add the acks from Daniel Thompson and Jingoo Han.
Changes since v3:
 - List the part numbers for the panel checked (Daniel Thompson)
Changes since v2:
 - Add this as a separate patch (Thierry Reding)
Changes since v1:
 - None

 drivers/video/backlight/pwm_bl.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 1c2289ddd555..698ec68bcdc9 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -54,10 +54,11 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
 	if (err < 0)
 		dev_err(pb->dev, "failed to enable power supply\n");
 
+	pwm_enable(pb->pwm);
+
 	if (pb->enable_gpio)
 		gpiod_set_value_cansleep(pb->enable_gpio, 1);
 
-	pwm_enable(pb->pwm);
 	pb->enabled = true;
 }
 
@@ -66,12 +67,12 @@ static void pwm_backlight_power_off(struct pwm_bl_data *pb)
 	if (!pb->enabled)
 		return;
 
-	pwm_config(pb->pwm, 0, pb->period);
-	pwm_disable(pb->pwm);
-
 	if (pb->enable_gpio)
 		gpiod_set_value_cansleep(pb->enable_gpio, 0);
 
+	pwm_config(pb->pwm, 0, pb->period);
+	pwm_disable(pb->pwm);
+
 	regulator_disable(pb->power_supply);
 	pb->enabled = false;
 }
-- 
2.15.1