linux-kernel - Re: [PATCH v6 1/5] ARM: davinci: da8xx: add usb phy clocks

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Message-ID: <2100252f-0165-96e7-2403-20e1f2d6e4e9@ti.com>
Date:   Wed, 26 Oct 2016 22:43:04 +0530
From:   Sekhar Nori <nsekhar@...com>
To:     David Lechner <david@...hnology.com>,
        Kevin Hilman <khilman@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>
CC:     Axel Haslam <ahaslam@...libre.com>,
        Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 1/5] ARM: davinci: da8xx: add usb phy clocks

On Wednesday 26 October 2016 10:07 PM, David Lechner wrote:
> On 10/26/2016 02:59 AM, Sekhar Nori wrote:
>> On Wednesday 26 October 2016 08:36 AM, David Lechner wrote:
>>> Up to this point, the USB phy clock configuration was handled
>>> manually in
>>> the board files and in the usb drivers. This adds proper clocks so that
>>> the usb drivers can use clk_get and clk_enable and not have to worry
>>> about
>>> the details. Also, the related code is removed from the board files and
>>> replaced with the new clock registration functions.
>>>
>>> Signed-off-by: David Lechner <david@...hnology.com>
>>> Signed-off-by: Axel Haslam <ahaslam@...libre.com>
>>> ---
>>>
>>> I have added "ARM: davinci: da8xx: Enable the usb20 "per" clk on
>>> phy_clk_enable"
>>> from Axel Haslam to this patch.
>>>
>>> In the review of Axel's patch, Sekhar said:
>>>
>>>> We should not be using a NULL device pointer here. Can you pass the
>>>> musb
>>>> device pointer available in the same file? Also, da850_clks[] in
>>>> da850.c
>>>> needs to be fixed to add the matching device name.
>>>
>>> However, the musb device may not be registered. The usb20_clk can be
>>> used to
>>> supply a 48MHz clock to USB 1.1 (ohci) without using the musb device.
>>> So, I am
>>> inclined to leave this as NULL.
>>
>> But clock look-up has nothing to do with device being registered AFAICT.
>> It is used to identify the clock consumer. Passing NULL there means the
>> clock is not associated with any device. Which is not correct as we are
>> specifically looking at MUSB module clock.
>>
>> Thanks,
>> Sekhar
>>
> 
> FWIW, clk_get() uses dev_name() to get the device name, which will
> return NULL until after the platform device is registered.

I believe you can set init_name in the device to setup an initial name
until registration.

> 
> I can add the device references anyway. However, this is complicated by
> the fact that the musb platform device declaration is inside of an #if
> IS_ENABLED(CONFIG_USB_MUSB_HDRC). I can either remove the #if or add
> more #if's. Do you have a preference on this?

Please remove the #if's. Usually device registration is never done
conditionally based on whether the driver is built or not. So this seems
incorrect anyway.

Thanks,
Sekhar