linux-kernel - [PATCH 2/2] video: ssd1307fb: Do not hard code active-low reset sequence

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Date:   Wed, 19 Sep 2018 11:18:44 +0200
From:   Michal Vokáč <michal.vokac@...ft.com>
To:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Shawn Guo <shawnguo@...nel.org>
Cc:     Fabio Estevam <fabio.estevam@....com>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-fbdev@...r.kernel.org,
        Michal Vokáč <michal.vokac@...ft.com>
Subject: [PATCH 2/2] video: ssd1307fb: Do not hard code active-low reset sequence

The SSD130x OLED display reset signal is active low. Now the reset
sequence is implemented in such a way that users are forced to
define reset-gpios as GPIO_ACTIVE_HIGH in DT to make the reset work.

Do not hard code the active-low sequence into the driver but instead
allow the user to specify the gpio as GPIO_ACTIVE_LOW to reflect
the real world.

The only single in-tree user of the display is converted and builds
fine.

Signed-off-by: Michal Vokáč <michal.vokac@...ft.com>
---
I am not really sure wheater this should be in one commit or the DT
changes should be done in separate commit. Just tell me and I will
split/merge the changes as you want. Thanks.

 arch/arm/boot/dts/imx28-cfa10036.dts | 3 ++-
 drivers/video/fbdev/ssd1307fb.c      | 4 ++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/arm/boot/dts/imx28-cfa10036.dts b/arch/arm/boot/dts/imx28-cfa10036.dts
index e54f5ab..be3406e 100644
--- a/arch/arm/boot/dts/imx28-cfa10036.dts
+++ b/arch/arm/boot/dts/imx28-cfa10036.dts
@@ -11,6 +11,7 @@
 
 /dts-v1/;
 #include "imx28.dtsi"
+#include <dt-bindings/gpio/gpio.h>
 
 / {
 	model = "Crystalfontz CFA-10036 Board";
@@ -95,7 +96,7 @@
 					pinctrl-names = "default";
 					pinctrl-0 = <&ssd1306_cfa10036>;
 					reg = <0x3c>;
-					reset-gpios = <&gpio2 7 0>;
+					reset-gpios = <&gpio2 7 GPIO_ACTIVE_LOW>;
 					solomon,height = <32>;
 					solomon,width = <128>;
 					solomon,page-offset = <0>;
diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c
index e7ae135..7b5bc42 100644
--- a/drivers/video/fbdev/ssd1307fb.c
+++ b/drivers/video/fbdev/ssd1307fb.c
@@ -728,10 +728,10 @@ static int ssd1307fb_probe(struct i2c_client *client,
 
 	if (par->reset) {
 		/* Reset the screen */
-		gpiod_set_value_cansleep(par->reset, 0);
-		udelay(4);
 		gpiod_set_value_cansleep(par->reset, 1);
 		udelay(4);
+		gpiod_set_value_cansleep(par->reset, 0);
+		udelay(4);
 	}
 
 	if (par->vbat_reg) {
-- 
2.1.4