linux-kernel - Re: [PATCH v2 0/2] usb: dwc3: support clocks and resets for DWC3 core

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Message-ID: <31be9c49-7562-1c06-7bf9-bafaea2f1c16@codeaurora.org>
Date:   Mon, 23 Apr 2018 17:11:39 -0700
From:   Manu Gautam <mgautam@...eaurora.org>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        linux-usb@...r.kernel.org,
        Felipe Balbi <felipe.balbi@...ux.intel.com>
Cc:     Rob Herring <robh@...nel.org>, Roger Quadros <rogerq@...com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jassi Brar <jaswinder.singh@...aro.org>,
        Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
        devicetree@...r.kernel.org, Felipe Balbi <balbi@...nel.org>,
        linux-kernel@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v2 0/2] usb: dwc3: support clocks and resets for DWC3 core

HI,


On 4/19/2018 4:03 AM, Masahiro Yamada wrote:
> In the current design of DWC3 driver,
> the DT typically becomes a nested structure like follows:
>
>   dwc3-glue {
>           compatible = "foo,dwc3";
>           ...
>
>           dwc3 {
>                   compatible = "snps,dwc3";
>                   ...
>           };
>   }
>
> The current DWC3 core (drivers/usb/dwc3/core.c) can not handle
> clocks / resets at all.
>
> The only solution we have now, is to put DWC3 core node under
> the glue layer node, then add clocks and resets there.
> Actually, dwc3-of-simple.c exists to handle clocks and resets.
>
> As always for digital circuits, DWC3 core IP itself needs clock input.
> This is specific to this IP.  So, supporting clocks and resets in
> dwc3/core.c makes sense.

Why can't dwc3-of-simple be used with this IP?
Adding core/reset handling in both core and glue drivers might
only add to confusion and I cant think of a reason why having a parent
node representing dwc3-of-simple glue would be any concern.
Or are you planning to remove dwc3-of-simple.c driver?

>
> In this version, the number of clocks (and names) is specific
> to this IP, with clock names taken from Synopsys datasheet.

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