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

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Date:   Mon, 5 Nov 2018 18:52:22 +0530
From:   Faiz Abbas <faiz_abbas@...com>
To:     Marc Kleine-Budde <mkl@...gutronix.de>,
        <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()

Hi Marc,

On Monday 05 November 2018 05:17 PM, Marc Kleine-Budde wrote:
> 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";
>>                         };
> 

Ok. Will implement that in v2.

Thanks,
Faiz