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Date:   Mon, 12 Oct 2020 08:47:15 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Catalin Marinas <catalin.marinas@arm.com>
Cc:     Ard Biesheuvel <ardb@kernel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Nicolas Saenz Julienne <nsaenzjulienne@suse.de>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
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        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
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        iommu@lists.linux-foundation.org, Rob Herring <robh+dt@kernel.org>,
        linux-rpi-kernel@lists.infradead.org,
        Frank Rowand <frowand.list@gmail.com>,
        Christoph Hellwig <hch@lst.de>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH 1/4] of/fdt: Update zone_dma_bits when running in
 bcm2711
Message-ID: <20201012064715.GA2548@lst.de>
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On Fri, Oct 09, 2020 at 06:10:52PM +0100, Catalin Marinas wrote:
> kdump wants DMA-able memory and,

DMAable by whom?  The only way to guranteed DMAable memory is to use
the DMA memory allocator(s) and pass a specific device to them.  Everyting
else is just fundamentally broken.  Note that even when device is not
DMAable we can still use swiotlb to access it.