linux-kernel - Re: [PATCH 1/6] phy: Add max_bitrate attribute & phy_get_max

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Message-ID: <1e708b81-ed63-7dbf-3120-d256c0ec76c6@pengutronix.de>
Date:   Mon, 5 Nov 2018 12:47:33 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Faiz Abbas <faiz_abbas@...com>, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, netdev@...r.kernel.org,
        linux-can@...r.kernel.org
Cc:     wg@...ndegger.com, robh+dt@...nel.org, mark.rutland@....com,
        kishon@...com
Subject: Re: [PATCH 1/6] phy: Add max_bitrate attribute &
 phy_get_max_bitrate()

On 11/05/2018 12:14 PM, Faiz Abbas wrote:
> Hi,
> 
> On Monday 05 November 2018 03:07 PM, Marc Kleine-Budde wrote:
>> On 11/05/2018 07:27 AM, Faiz Abbas wrote:
>>> I remove the transceiver child node binding documentation in patch 5/6.
>>>
>>> The existing implementation is pretty limiting as it just has a child
>>> node with no associated device. What if a transceiver requires its own
>>> configurations before it can start sending/receiving messages (for
>>> example, my usecase requires it to pull the standby line low)?
>>>
>>> I think that can be solved by implementing the transceiver as a phy and
>>> exposing a generic get_max_bitrate API. That way, the transceiver device
>>> can do all its startup configuration in the phy probe function.
>>>
>>> In any case, do suggest if you have a better idea on how to implement
>>> pull gpio low requirement.
>>
>> As long as we don't have any proper transceiver/phy driver, that does
>> more than swtich on/off a GPIO, please add a "xceiver" regulator to your
>> driver. Look for:
>>
>>> devm_regulator_get(&pdev->dev, "xceiver");
>>
> 
> The transceiver is not specific to m_can. The pull down would be
> required even if it were connected to some other controller.

Ok, this is a quite common pattern. For the fsl/nxp boards we add the
regulator to the board dts. See "imx28-evk.dts" for example:

>                         can0: can@...32000 {
>                                 pinctrl-names = "default";
>                                 pinctrl-0 = <&can0_pins_a>;
>                                 xceiver-supply = <&reg_can_3v3>;
>                                 status = "okay";
>                         };
> 
>                         can1: can@...34000 {
>                                 pinctrl-names = "default";
>                                 pinctrl-0 = <&can1_pins_a>;
>                                 xceiver-supply = <&reg_can_3v3>;
>                                 status = "okay";
>                         };

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
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