[5.10.y-cip,01/27] dt-bindings: pincfg-node: Add "output-impedance-ohms" property

Commit Message

Lad Prabhakar Jan. 31, 2022, 12:18 p.m. UTC

commit 7388fa8acfce2c3b41babc53c3f3d0b247b098af upstream.

On RZ/G2L SoC for Group-B pins, output impedance can be configured. This
patch documents "output-impedance-ohms" property in pincfg-node.yaml so
that other platforms requiring such feature can make use of this property.

Signed-off-by: Lad Prabhakar <[e-mail]>
Reviewed-by: Biju Das <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Reviewed-by: Linus Walleij <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Geert Uytterhoeven <[e-mail]>
Signed-off-by: Lad Prabhakar <[e-mail]>
---
 Documentation/devicetree/bindings/pinctrl/pincfg-node.yaml | 3 +++
 1 file changed, 3 insertions(+)

Comments

Pavel Machek Aug. 13, 2022, 1:45 p.m. UTC | #1

Hi!

> +++ b/Documentation/devicetree/bindings/pinctrl/pincfg-node.yaml
> @@ -114,6 +114,9 @@ properties:
>      description: enable output on a pin without actively driving it
>        (such as enabling an output buffer)
>  
> +  output-impedance-ohms:
> +    description: set the output impedance of a pin to at most X ohms
> +

Is that right description ("at most")? Later in the bindings you
support specific values, which IMO makes sense, without relying on the
"at most" part.

If dts asks for 1000 ohms impedance and implementation sets it to 10
ohms, that will cause problems, no?

Best regards,
								Pavel

Lad Prabhakar Aug. 14, 2022, 9:37 p.m. UTC | #2

Hi Pavel,

Thank you for the review.

> -----Original Message-----
> From: Pavel Machek <[e-mail]>
> Sent: 13 August 2022 14:45
> To: Prabhakar Mahadev Lad <[e-mail]>
> Cc: [e-mail]; Nobuhiro Iwamatsu <[e-mail]>; Pavel Machek
> <[e-mail]>; Biju Das <[e-mail]>
> Subject: Re: [PATCH 5.10.y-cip 01/27] dt-bindings: pincfg-node: Add "output-impedance-ohms" property
> 
> Hi!
> 
> > +++ b/Documentation/devicetree/bindings/pinctrl/pincfg-node.yaml
> > @@ -114,6 +114,9 @@ properties:
> >      description: enable output on a pin without actively driving it
> >        (such as enabling an output buffer)
> >
> > +  output-impedance-ohms:
> > +    description: set the output impedance of a pin to at most X ohms
> > +
> 
> Is that right description ("at most")? Later in the bindings you support specific values, which IMO
> makes sense, without relying on the "at most" part.
> 
I have followed the description text as used in pincfg-node.yaml file previously.

> If dts asks for 1000 ohms impedance and implementation sets it to 10 ohms, that will cause problems,
> no?
> 
I think since pincfg-node.yaml file is generic, hence this description, later the dt binding file which will actually uses this property will have to specify what values are appropriate that needs to be set in dts/i.


Cheers,
Prabhakar

> Best regards,
> 								Pavel
> --
> DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

Patch

diff --git a/Documentation/devicetree/bindings/pinctrl/pincfg-node.yaml b/Documentation/devicetree/bindings/pinctrl/pincfg-node.yaml
index 71ed0a9def84..4b22a9e3a447 100644
--- a/Documentation/devicetree/bindings/pinctrl/pincfg-node.yaml
+++ b/Documentation/devicetree/bindings/pinctrl/pincfg-node.yaml
@@ -114,6 +114,9 @@  properties:
     description: enable output on a pin without actively driving it
       (such as enabling an output buffer)
 
+  output-impedance-ohms:
+    description: set the output impedance of a pin to at most X ohms
+
   output-low:
     type: boolean
     description: set the pin to output mode with low level