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

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Date:   Wed, 26 Oct 2016 11:37:04 -0500
From:   David Lechner <david@...hnology.com>
To:     Sekhar Nori <nsekhar@...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 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 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?