Add binding for Sitronix ST7920 display.

Signed-off-by: Iker Pedrosa <ikerpedrosam@gmail.com>
---
 .../bindings/display/sitronix,st7920.yaml          | 50 ++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/Documentation/devicetree/bindings/display/sitronix,st7920.yaml b/Documentation/devicetree/bindings/display/sitronix,st7920.yaml
new file mode 100644
index 0000000000000000000000000000000000000000..b4c16825f254f1b8345a2532271042350e3a5e26
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/sitronix,st7920.yaml
@@ -0,0 +1,50 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/sitronix,st7920.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Sitronix ST7920 LCD Display Controllers
+
+maintainers:
+  - Iker Pedrosa <ikerpedrosam@gmail.com>
+
+description:
+  The Sitronix ST7920 is a controller for monochrome dot-matrix graphical LCDs,
+  most commonly used for 128x64 pixel displays.
+
+properties:
+  compatible:
+    const: sitronix,st7920
+
+  reg:
+    maxItems: 1
+
+  spi-max-frequency:
+    maximum: 600000
+
+required:
+  - compatible
+  - reg
+  - spi-max-frequency
+
+allOf:
+  - $ref: /schemas/spi/spi-peripheral-props.yaml#
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        display@0 {
+            compatible = "sitronix,st7920";
+            reg = <0>;
+            spi-max-frequency = <600000>;
+            spi-cs-high;
+        };
+    };

-- 
2.51.0

On 07/10/2025 02:48, Iker Pedrosa wrote:
> +
> +properties:
> +  compatible:
> +    const: sitronix,st7920
> +
> +  reg:
> +    maxItems: 1
> +
> +  spi-max-frequency:
> +    maximum: 600000
> +

Datasheet I found on the web clearly stats you have at least VDD and XRESET.

Your binding is still not complete (and I asked...), while it should be
complete (See writing bindings doc).


Best regards,
Krzysztof

El mar, 7 oct 2025 a las 11:12, Krzysztof Kozlowski
(<krzk@kernel.org>) escribió:
>
> On 07/10/2025 02:48, Iker Pedrosa wrote:
> > +
> > +properties:
> > +  compatible:
> > +    const: sitronix,st7920
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  spi-max-frequency:
> > +    maximum: 600000
> > +
>
> Datasheet I found on the web clearly stats you have at least VDD and XRESET.
>
> Your binding is still not complete (and I asked...), while it should be
> complete (See writing bindings doc).

Thanks for the information. You're correct; I'll add the two suggested
properties, XRESET and VDD, to the binding. I'll also implement the
XRESET handling in the driver.

I missed the XRESET pin because my testing setup was working without
it. For VDD, it's currently connected to the RPi's 5V output.

While other Sitronix display bindings in the kernel don't currently
define a supply property (running "git grep -i supply
Documentation/devicetree/bindings/display/sitronix*" confirmed this),
I agree it should be included for a complete binding. I'll define it
as a fixed-regulator in my display DT node.

>
>
> Best regards,
> Krzysztof