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Date:   Mon, 30 Sep 2019 01:20:55 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     Rob Herring <robh@kernel.org>, DTML <devicetree@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        linux-pci <linux-pci@vger.kernel.org>,
        Nicolas Saenz Julienne <nsaenzjulienne@suse.de>,
        Robin Murphy <robin.murphy@arm.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Stefan Wahren <wahrenst@gmx.net>,
        Frank Rowand <frowand.list@gmail.com>,
        Marek Vasut <marek.vasut@gmail.com>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Simon Horman <horms+renesas@verge.net.au>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Oza Pawandeep <oza.oza@broadcom.com>,
        Christoph Hellwig <hch@infradead.org>,
        Thierry Reding <thierry.reding@gmail.com>
Subject: Re: [PATCH 00/11] of: dma-ranges fixes and improvements
Message-ID: <20190930082055.GA21971@infradead.org>
References: <20190927002455.13169-1-robh@kernel.org>
 <CAK8P3a0oct0EOMi5t4BmpgdkiBM+LjC+2pTST4hcvNCa3MGLmw@mail.gmail.com>
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On Sun, Sep 29, 2019 at 01:16:20PM +0200, Arnd Bergmann wrote:
> On a semi-related note, Thierry asked about one aspect of the dma-ranges
> property recently, which is the behavior of dma_set_mask() and related
> functions when a driver sets a mask that is larger than the memory
> area in the bus-ranges but smaller than the available physical RAM.
> As I understood Thierry's problem and the current code, the generic
> dma_set_mask() will either reject the new mask entirely or override
> the mask set by of_dma_configure, but it fails to set a correct mask
> within the limitations of the parent bus in this case.

There days dma_set_mask will only reject a mask if it is too small
to be supported by the hardware.  Larger than required masks are now
always accepted.