linux-kernel - Re: [PATCH 1/4] dt-bindings: phy: Add binding for TI TCAN104x CAN transceivers

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Message-ID: <20210413074106.gvgtjkofyrdp5yxt@pengutronix.de>
Date:   Tue, 13 Apr 2021 09:41:06 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Rob Herring <robh@...nel.org>
Cc:     Aswath Govindraju <a-govindraju@...com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Kishon Vijay Abraham I <kishon@...com>,
        Lokesh Vutla <lokeshvutla@...com>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Chandrasekar Ramakrishnan <rcsekar@...sung.com>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Vinod Koul <vkoul@...nel.org>, linux-can@...r.kernel.org,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-phy@...ts.infradead.org
Subject: Re: [PATCH 1/4] dt-bindings: phy: Add binding for TI TCAN104x CAN
 transceivers

On 12.04.2021 12:49:56, Rob Herring wrote:
> On Mon, Apr 12, 2021 at 12:19:30PM +0200, Marc Kleine-Budde wrote:
> > On 4/9/21 3:40 PM, Aswath Govindraju wrote:
> > > Add binding documentation for TI TCAN104x CAN transceivers.
> > > 
> > > Signed-off-by: Aswath Govindraju <a-govindraju@...com>
> > > ---
> > >  .../bindings/phy/ti,tcan104x-can.yaml         | 56 +++++++++++++++++++
> > >  1 file changed, 56 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/phy/ti,tcan104x-can.yaml
> > > 
> > > diff --git a/Documentation/devicetree/bindings/phy/ti,tcan104x-can.yaml b/Documentation/devicetree/bindings/phy/ti,tcan104x-can.yaml
> > > new file mode 100644
> > > index 000000000000..4abfc30a97d0
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/phy/ti,tcan104x-can.yaml
> > > @@ -0,0 +1,56 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: "http://devicetree.org/schemas/phy/ti,tcan104x-can.yaml#"
> > > +$schema: "http://devicetree.org/meta-schemas/core.yaml#"
> > > +
> > > +title: TCAN104x CAN TRANSCEIVER PHY
> > > +
> > > +maintainers:
> > > +  - Aswath Govindraju <a-govindraju@...com>
> > > +
> > > +properties:
> > > +  $nodename:
> > > +    pattern: "^tcan104x-phy"
> > > +
> > > +  compatible:
> > > +    enum:
> > > +      - ti,tcan1042
> > > +      - ti,tcan1043
> > 
> > Can you create a generic standby only and a generic standby and enable transceiver?
> 
> As a fallback compatible fine, but no generic binding please. A generic 
> binding can't describe any timing requirements between the 2 GPIO as 
> well as supplies when someone wants to add those (and they will).

Right - that makes sense.

> > > +
> > > +  '#phy-cells':
> > > +    const: 0
> > > +
> > > +  standby-gpios:
> > > +    description:
> > > +      gpio node to toggle standby signal on transceiver
> > > +    maxItems: 1
> > > +
> > > +  enable-gpios:
> > > +    description:
> > > +      gpio node to toggle enable signal on transceiver
> > > +    maxItems: 1
> > > +
> > > +  max-bitrate:
> > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > +    description:
> > > +      max bit rate supported in bps
> 
> We already have 'max-speed' for serial devices, use that.

There is already the neither Ethernet PHY (PHYLINK/PHYLIB) nor generic
PHY (GENERIC_PHY) can-transceiver binding
Documentation/devicetree/bindings/net/can/can-transceiver.yaml which
specifies max-bitrate. I don't have strong feelings whether to use
max-bitrate or max-speed.

Speaking about Ethernet PHYs, what are to pros and cons to use the
generic PHY compared to the Ethernet PHY infrastructure?

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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