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Date:   Tue, 11 Jun 2019 09:54:39 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc:     Christoph Hellwig <hch@lst.de>,
        Larry Finger <Larry.Finger@lwfinger.net>,
        Aaro Koskinen <aaro.koskinen@iki.fi>,
        Christian Zigotzky <chzigotzky@xenosoft.de>,
        Michael Ellerman <mpe@ellerman.id.au>,
        linuxppc-dev@lists.ozlabs.org, linux-wireless@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [BISECTED REGRESSION] b43legacy broken on G4 PowerBook
Message-ID: <20190611075439.GB21815@lst.de>
References: <20190605225059.GA9953@darkstar.musicnaut.iki.fi> <73da300c-871c-77ac-8a3a-deac226743ef@lwfinger.net> <7697a9d10777b28ae79fdffdde6d0985555f6310.camel@kernel.crashing.org> <3ed1ccfe-d7ca-11b9-17b3-303d1ae1bb0f@lwfinger.net> <c91ccbddd6a58dbee5705f10ed1d98fb44bd8f8d.camel@kernel.crashing.org> <20190611060816.GA20158@lst.de> <fdfc817d1dcdc83f5bc45f0ab12cbce0c61e6702.camel@kernel.crashing.org> <b30ced162fa96d0ca63b8b9629d6fe9bc5c78746.camel@kernel.crashing.org>
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On Tue, Jun 11, 2019 at 04:59:54PM +1000, Benjamin Herrenschmidt wrote:
> Ah stupid me ... it's dma_set_mask that failed, since it has no idea
> that the calling driver is limited to lowmem.
> 
> That's also why the "wrong" patch worked.
> 
> So yes, a ZONE_DMA at 30-bits will work, though it's somewhat overkill.

Well, according to Larry it doesn't actually work, which is odd.