linux-kernel - Re: [PATCH] usb: dwc3: host: inherit dma configuration from parent dev

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Date:   Thu, 08 Sep 2016 14:14:50 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Grygorii Strashko <grygorii.strashko@...com>
Cc:     Felipe Balbi <balbi@...nel.org>,
        Peter Chen <hzpeterchen@...il.com>, Leo Li <pku.leo@...il.com>,
        Russell King - ARM Linux <linux@....linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        Sekhar Nori <nsekhar@...com>,
        lkml <linux-kernel@...r.kernel.org>,
        Stuart Yoder <stuart.yoder@....com>,
        Scott Wood <oss@...error.net>,
        David Fisher <david.fisher1@...opsys.com>,
        "Thang Q. Nguyen" <tqnguyen@....com>,
        Alan Stern <stern@...land.harvard.edu>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] usb: dwc3: host: inherit dma configuration from parent dev

On Thursday, September 8, 2016 3:02:56 PM CEST Grygorii Strashko wrote:
> dwc3: probe()
>         if (!&pdev->dev->of_node)
>                  legacy case - hard-code DMA props
>                 dwc->sysdev = &pdev->dev;

The PCI case will fall into this too, as we almost never have an
->of_node pointer for a PCI device.

Do we actually have any legacy dwc3 users in Linux that are neither DT
nor PCI based? Maybe we can just skip that.

>         else
>                 dev = &pdev->dev;
>                 do {
>                         if (is_device_dma_capable(dev)) {
>                                 dwc->sysdev = dev;
>                                 break;
>                         }
>                    dev = dev->parent;
>                 while (dev);
>                 ^this cycle can be limited in depth (2 for PCI)

Right, this could work by itself and looks generic enough.

	Arnd