linux-kernel - [PATCH fbdev-for-next 1/2] dt-bindings: display: ssd1307fb: Add reset-active-low property

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Date:   Fri, 2 Nov 2018 14:56:32 +0000
From:   Vokáč Michal <Michal.Vokac@...ft.com>
To:     Rob Herring <robh+dt@...nel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
CC:     "linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Jyri Sarha <jsarha@...com>,
        Vokáč Michal <Michal.Vokac@...ft.com>
Subject: [PATCH fbdev-for-next 1/2] dt-bindings: display: ssd1307fb: Add
 reset-active-low property

This reverts commit 519b4dba586198eed8f72ba07bc71808af2e0e32.
It is true that the actual implementation has never been there. But
contrary to what the reverted commit message says it does make sense
to add it.

Current implementation of the reset signal is hard-coded to active low
with the assumption that reset-gpios is specified as GPIO_ACTIVE_HIGH.
That is technically wrong as the DTS authors should know that SSD130x
displays need active low reset and hence they are temped to use
GPIO_ACTIVE_LOW. But with that the reset is broken. So reset-acive-low
property can be used to invert the signal once again to fix this.

Signed-off-by: Michal Vokáč <michal.vokac@...ft.com>
---
 Documentation/devicetree/bindings/display/ssd1307fb.txt | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/display/ssd1307fb.txt b/Documentation/devicetree/bindings/display/ssd1307fb.txt
index 209d931..a5ead10 100644
--- a/Documentation/devicetree/bindings/display/ssd1307fb.txt
+++ b/Documentation/devicetree/bindings/display/ssd1307fb.txt
@@ -16,6 +16,8 @@ Required properties:
 Optional properties:
   - reset-gpios: The GPIO used to reset the OLED display, if available. See
                  Documentation/devicetree/bindings/gpio/gpio.txt for details.
+  - reset-active-low: Bool flag to indicate the GPIO specified in "reset-gpios"
+                      property is active low.
   - vbat-supply: The supply for VBAT
   - solomon,segment-no-remap: Display needs normal (non-inverted) data column
                               to segment mapping
@@ -35,7 +37,7 @@ ssd1307: oled@3c {
         compatible = "solomon,ssd1307fb-i2c";
         reg = <0x3c>;
         pwms = <&pwm 4 3000>;
-        reset-gpios = <&gpio2 7>;
+        reset-gpios = <&gpio2 7 GPIO_ACTIVE_LOW>;
         reset-active-low;
 };
 
@@ -43,7 +45,7 @@ ssd1306: oled@3c {
         compatible = "solomon,ssd1306fb-i2c";
         reg = <0x3c>;
         pwms = <&pwm 4 3000>;
-        reset-gpios = <&gpio2 7>;
+        reset-gpios = <&gpio2 7 GPIO_ACTIVE_LOW>;
         reset-active-low;
         solomon,com-lrremap;
         solomon,com-invdir;
-- 
2.1.4