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Date:   Tue, 24 Sep 2019 23:25:54 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     James Bottomley <James.Bottomley@HansenPartnership.com>
Cc:     Sven Schnelle <svens@stackframe.org>,
        Christoph Hellwig <hch@lst.de>, Helge Deller <deller@gmx.de>,
        linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: allow larger than require DMA masks
Message-ID: <20190924212554.GA31357@lst.de>
References: <20190215144559.8777-1-hch@lst.de> <20190923211415.GA1875@stackframe.org> <1569286782.3657.29.camel@HansenPartnership.com>
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On Mon, Sep 23, 2019 at 08:59:42PM -0400, James Bottomley wrote:
> > 	if (mask > ~0U)
> > ?     ?       return 0;
> > 
> > Removing the if() makes the DMA mapping work. It's almost midnight
> > here, so i won't look into that any further today. Does anyone have
> > an opinion on this behaviour? Otherwise i will look a bit more into
> > this in the next days.
> 
> The reason for the if was to kick the device into 32 bit descriptors,
> which are usually more efficient, especially with older dual descriptor
> format cards like we have on parisc systems.

These days we use the dma_get_required_mask API to query for that.

Svens patch looks right for how we are now using the DMA mask setting
API.