[PATCH v4 03/10] dt-bindings: serial: add documentation for Bouffalolab UART Driver

[Jisheng Zhang]

On Thu, May 18, 2023 at 10:00:50PM -0500, Samuel Holland wrote:
> Hi Jisheng,

Hi Samuel,

> 
> On 5/18/23 10:22, Jisheng Zhang wrote:
> > Add bindings doc for Bouffalolab UART Driver
> > 
> > Signed-off-by: Jisheng Zhang <jszhang at kernel.org>
> > Acked-by: Palmer Dabbelt <palmer at rivosinc.com>
> > ---
> >  .../serial/bouffalolab,bl808-uart.yaml        | 47 +++++++++++++++++++
> >  1 file changed, 47 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/serial/bouffalolab,bl808-uart.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/serial/bouffalolab,bl808-uart.yaml b/Documentation/devicetree/bindings/serial/bouffalolab,bl808-uart.yaml
> > new file mode 100644
> > index 000000000000..0ef858e50efb
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/serial/bouffalolab,bl808-uart.yaml
> > @@ -0,0 +1,47 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +# Copyright (C) 2022 Jisheng Zhang <jszhang at kernel.org>
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/serial/bouffalolab,bl808-uart.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Bouffalolab UART Controller
> > +
> > +maintainers:
> > +  - Jisheng Zhang <jszhang at kernel.org>
> > +
> > +allOf:
> > +  - $ref: serial.yaml#
> > +
> > +properties:
> > +  compatible:
> > +    const: bouffalolab,bl808-uart
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  interrupts:
> > +    maxItems: 1
> > +
> > +  clocks:
> > +    maxItems: 1
> 
> This is not complete. There are separate APB and module (baud) clocks,
> as well as a peripheral reset line. If we are going to keep the binding
> stable, these need to be described up front.

IIUC, the only requirement is to keep the driver compatible with both
new dts and old dts. clk tree and reset can be added latter. I have seen
sevral such examples from other SoCs' mainline progress.

> 
> (I still don't fully understand the clock tree, and so far that has been
> the main blocker for me sending a follow-up series with additional
> bindings for hardware that's otherwise already supported, like the
> Ethernet MAC.)
> 
> Regards,
> Samuel
> 
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - interrupts
> > +  - clocks
> > +
> > +unevaluatedProperties: false
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/interrupt-controller/irq.h>
> > +
> > +    uart0: serial at 30002000 {
> > +        compatible = "bouffalolab,bl808-uart";
> > +        reg = <0x30002000 0x1000>;
> > +        interrupts = <53 IRQ_TYPE_LEVEL_HIGH>;
> > +        clocks = <&xtal>;
> > +    };
> > +...
>