linux-kernel - Re: [PATCH 05/67] dma-mapping: replace PCI_DMA_BUS_IS_PHYS with a flag in struct dma_map

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Date:   Tue, 9 Jan 2018 16:55:50 +0100
From:   Jesper Nilsson <jesper.nilsson@...s.com>
To:     Christoph Hellwig <hch@....de>
Cc:     iommu@...ts.linux-foundation.org, linux-mips@...ux-mips.org,
        linux-ia64@...r.kernel.org, linux-sh@...r.kernel.org,
        sparclinux@...r.kernel.org, Guan Xuetao <gxt@...c.pku.edu.cn>,
        linux-arch@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-c6x-dev@...ux-c6x.org, linux-hexagon@...r.kernel.org,
        x86@...nel.org, linux-snps-arc@...ts.infradead.org,
        adi-buildroot-devel@...ts.sourceforge.net,
        linux-m68k@...ts.linux-m68k.org, patches@...ups.riscv.org,
        linux-metag@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Michal Simek <monstr@...str.eu>, linux-parisc@...r.kernel.org,
        linux-cris-kernel@...s.com, linux-kernel@...r.kernel.org,
        linux-alpha@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 05/67] dma-mapping: replace PCI_DMA_BUS_IS_PHYS with a
 flag in struct dma_map_ops

On Fri, Dec 29, 2017 at 09:18:09AM +0100, Christoph Hellwig wrote:
> The current PCI_DMA_BUS_IS_PHYS decided if a dma implementation is bound
> by the dma mask in the device because it directly maps to a physical
> address range (modulo an offset in the device), or if it is virtualized
> by an iommu and can map any address (that includes virtual iommus like
> swiotlb).  The problem with this scheme is that it is per-architecture and
> not per dma_ops instance, and we are growing more and more setups that
> have multiple different dma operations in use on a single system, for
> which this scheme can't provide a correct answer.  Depending on the
> architecture that means we either get a false positive or false negative
> at the moment.
> 
> This patch instead extents the is_phys flag in struct dma_map_ops that
> is currently only used by a few architectures to be used tree wide.
> 
> Note that this means that we now need a struct device parent in the
> Scsi_Host or netdevice.  Every modern driver has these, but there might
> still be a few outdated legacy drivers out there, which now won't make
> an intelligent decision.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>

For the CRIS part:

Acked-by: Jesper Nilsson <jesper.nilsson@...s.com>

> ---
>  arch/cris/arch-v32/drivers/pci/dma.c  |  1 +
>  arch/cris/include/asm/pci.h           |  6 ------

/^JN - Jesper Nilsson
-- 
               Jesper Nilsson -- jesper.nilsson@...s.com