linux-kernel - Re: [PATCH v5 0/5] iommu: M1 Pro/Max DART support

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Date:   Thu, 22 Sep 2022 23:05:59 +0900
From:   Hector Martin <marcan@...can.st>
To:     Janne Grunau <j@...nau.net>, iommu@...ts.linux.dev
Cc:     Konrad Dybcio <konrad.dybcio@...ainline.org>,
        asahi@...ts.linux.dev, Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Joerg Roedel <joro@...tes.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Mark Kettenis <mark.kettenis@...all.nl>,
        Rob Herring <robh+dt@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Sven Peter <sven@...npeter.dev>, Will Deacon <will@...nel.org>,
        devicetree@...r.kernel.org, iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 0/5] iommu: M1 Pro/Max DART support

On 16/09/2022 18.41, Janne Grunau wrote:
> Hej,
> 
> this is the next attempt adding support for the DART found in Apple's
> M1 Pro/Max/Ultra. This adds a separate io-pgtable implementation for
> DART. As already mentioned in v2 the pte format is not fully compatible
> with io-pgtable-arm. Especially the 2nd least significant bit is used
> and is not available to tag tables/pages.
> io-pgtable-dart.c is copied from io-pgtable-arm.c and support for
> unused features is removed. Support for 4k IO pages is left for A7 to
> A11 SoCs as there's work underway to run Linux on them.
> 
> The incompatibilities between both Apple DART pte seems manageable in
> their own io-pgtable implementation. A short list of the known
> differences:
> 
>  - the physical addresses are shifted left by 4 bits and and have 2 more
>    bits inside the PTE entries
>  - the read/write protection flags are at a different position
>  - the subpage protection feature is now mandatory. For Linux we can
>    just configure it to always allow access to the entire page.
>  - BIT(1) tags "uncached" mappings (used for the display controller)
> 
> There is second type of DART (t8110) present on M1 Pro/Max SoCs which
> uses the same PTE format as t6000.
> 
> Changes in v5:
> - collected Sven's ack
> - minor fixes in "iommu/io-pgtable: Move Apple DART support to its own
>   file"
> 
> Changes in v4:
> - split dart and io-pgtable-dart build to allow building dart as module
> - add missing "SELECT IOMMU_IO_PGTABLE"
> - made map/unmap_pages/iova_to_phys inon-recursive
> - replace pgd concatenation with multiple table handling
> - simplified config and page size checks
> - collected Robin's Ack
> 
> Changes in v3:
> - move APPLE_DART to its own io-pgtable implementation, copied from
>   io-pgtable-arm and simplified
> 
> Changes in v2:
> - added Rob's Acked-by:
> - add APPLE_DART2 io-pgtable format
> 
> Janne Grunau (1):
>   iommu/io-pgtable: Move Apple DART support to its own file
> 
> Sven Peter (4):
>   dt-bindings: iommu: dart: add t6000 compatible
>   iommu/io-pgtable: Add DART subpage protection support
>   iommu/io-pgtable-dart: Add DART PTE support for t6000
>   iommu: dart: Support t6000 variant
> 
>  .../devicetree/bindings/iommu/apple,dart.yaml |   4 +-
>  MAINTAINERS                                   |   1 +
>  drivers/iommu/Kconfig                         |  13 +-
>  drivers/iommu/Makefile                        |   1 +
>  drivers/iommu/apple-dart.c                    |  24 +-
>  drivers/iommu/io-pgtable-arm.c                |  63 ---
>  drivers/iommu/io-pgtable-dart.c               | 470 ++++++++++++++++++
>  drivers/iommu/io-pgtable.c                    |   3 +
>  include/linux/io-pgtable.h                    |   1 +
>  9 files changed, 512 insertions(+), 68 deletions(-)
>  create mode 100644 drivers/iommu/io-pgtable-dart.c
> 

For the whole series, modulo the trivial warning I mentioned:

Acked-by: Hector Martin <marcan@...can.st>

Let's get this merged please, it's been blocking t6000 support for a
long time now :)

- Hector