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


Lad Prabhakar
 

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 <prabhakar.mahadev-lad.rj@...>
Reviewed-by: Biju Das <biju.das.jz@...>
Acked-by: Rob Herring <robh@...>
Reviewed-by: Linus Walleij <linus.walleij@...>
Link: https://lore.kernel.org/r/20211027134509.5036-2-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@...>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...>
---
Documentation/devicetree/bindings/pinctrl/pincfg-node.yaml | 3 +++
1 file changed, 3 insertions(+)

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
--
2.17.1


Pavel Machek
 

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


Lad Prabhakar
 

Hi Pavel,

Thank you for the review.

-----Original Message-----
From: Pavel Machek <pavel@...>
Sent: 13 August 2022 14:45
To: Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...>
Cc: cip-dev@...; Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@...>; Pavel Machek
<pavel@...>; Biju Das <biju.das.jz@...>
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