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

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Message-ID: <5224196.iEv3ICfjjt@wuerfel>
Date:   Fri, 02 Sep 2016 15:10:34 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     Robin Murphy <robin.murphy@....com>,
        Felipe Balbi <balbi@...nel.org>, Leo Li <pku.leo@...il.com>,
        Grygorii Strashko <grygorii.strashko@...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>
Subject: Re: [PATCH] usb: dwc3: host: inherit dma configuration from parent dev

On Friday, September 2, 2016 12:55:33 PM CEST Robin Murphy wrote:
> 
> Huh? There's only no DMA description in DT if the device can be assumed
> to be happy with the defaults. Anything else should be using
> "dma-ranges", "dma-coherent", etc. to describe non-default integration
> aspects. For devices with an inherent fixed addressing capability !=32
> bits, then it's down to the driver to call dma_set_mask() appropriately
> to override the default 32-bit mask (which is not unique to OF-probed
> devices either).

The iommu configuration would be the main other one worth mentioning.

Note that there is a known bug with dma_set_mask(), which always succeeds
at the moment, even if the dma-ranges limit the possible addresses
in a way that should fail.

	Arnd