linux-kernel - [PATCH v3 0/2] iommu/arm-smmu: Split pagetable support

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Message-Id: <1565216386-28309-1-git-send-email-jcrouse@codeaurora.org>
Date:   Wed,  7 Aug 2019 16:19:44 -0600
From:   Jordan Crouse <jcrouse@...eaurora.org>
To:     freedreno@...ts.freedesktop.org
Cc:     jean-philippe.brucker@....com, linux-arm-msm@...r.kernel.org,
        robin.murphy@....com, Will Deacon <will@...nel.org>,
        Zhen Lei <thunder.leizhen@...wei.com>,
        Rob Herring <robh@...nel.org>, linux-kernel@...r.kernel.org,
        iommu@...ts.linux-foundation.org, Joerg Roedel <joro@...tes.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH v3 0/2] iommu/arm-smmu: Split pagetable support

This is part of an ongoing evolution for enabling split pagetable support for
arm-smmu. Previous versions can be found [1].

In the discussion for v2 Robin pointed out that this is a very Adreno specific
use case and that is exactly true. Not only do we want to configure and use a
pagetable in the TTBR1 space, we also want to configure the TTBR0 region but
not allocate a pagetable for it or touch it until the GPU hardware does so. As
much as I want it to be a generic concept it really isn't.

This revision leans into that idea. Most of the same io-pgtable code is there
but now it is wrapped as an Adreno GPU specific format that is selected by the
compatible string in the arm-smmu device.

Additionally, per Robin's suggestion we are skipping creating a TTBR0 pagetable
to save on wasted memory.

This isn't as clean as I would like it to be but I think that this is a better
direction than trying to pretend that the generic format would work.

I'm tempting fate by posting this and then taking some time off, but I wanted
to try to kick off a conversation or at least get some flames so I can try to
refine this again next week. Please take a look and give some advice on the
direction.

[1] https://patchwork.freedesktop.org/series/63403/

Jordan

Jordan Crouse (2):
  iommu/io-pgtable-arm: Add support for ARM_ADRENO_GPU_LPAE io-pgtable
    format
  iommu/arm-smmu: Add support for Adreno GPU pagetable formats

 drivers/iommu/arm-smmu.c       |   8 +-
 drivers/iommu/io-pgtable-arm.c | 214 ++++++++++++++++++++++++++++++++++++++---
 drivers/iommu/io-pgtable.c     |   1 +
 include/linux/io-pgtable.h     |   2 +
 4 files changed, 209 insertions(+), 16 deletions(-)

-- 
2.7.4