linux-kernel - Re: [RFC PATCH 0/4] Stop losing firmware-set DMA masks

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Date:   Tue, 10 Jul 2018 20:02:32 +0200
From:   Christoph Hellwig <hch@....de>
To:     Robin Murphy <robin.murphy@....com>
Cc:     m.szyprowski@...sung.com, iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org, linux-acpi@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        lorenzo.pieralisi@....com, hanjun.guo@...aro.org,
        sudeep.holla@....com, robh+dt@...nel.org, frowand.list@...il.com,
        gregkh@...uxfoundation.org, joro@...tes.org, x86@...nel.org,
        Palmer Dabbelt <palmer@...ive.com>,
        linux-riscv@...ts.infradead.org
Subject: Re: [RFC PATCH 0/4] Stop losing firmware-set DMA masks

> These patches attempt to deal with this in the simplest way possible by
> generalising the specific quirk for 32-bit bridges into an arbitrary
> mask which can then also be plumbed into the firmware code. In the
> interest of being minimally invasive, I've only included a point fix
> for the IOMMU issue as seen on arm64 - there may be further tweaks
> needed in DMA ops to catch all possible incarnations of this problem,
> but this initial RFC is mostly about the impact beyond the dma-mapping
> subsystem itself.

Thanks, this looks very nice to me.

In fact it probably solves the RISC-V/Xiling problem as well if we can
just add the dma-ranges property to the device tree for the affected
systems.  Palmer, do you know how easily the DT could be updated for
that case?

> 
> Robin.
> 
> 
> [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2018-May/580804.html
> [2] http://lists.infradead.org/pipermail/linux-arm-kernel/2016-December/474443.html
> 
> Robin Murphy (4):
>   dma-mapping: Generalise dma_32bit_limit flag
>   ACPI/IORT: Set bus DMA mask as appropriate
>   of/device: Set bus DMA mask as appropriate
>   iommu/dma: Respect bus DMA limit for IOVAs
> 
>  arch/x86/kernel/pci-dma.c | 2 +-
>  drivers/acpi/arm64/iort.c | 1 +
>  drivers/iommu/dma-iommu.c | 3 +++
>  drivers/of/device.c       | 1 +
>  include/linux/device.h    | 6 +++---
>  kernel/dma/direct.c       | 2 +-
>  6 files changed, 10 insertions(+), 5 deletions(-)
> 
> -- 
> 2.17.1.dirty
---end quoted text---