Re: [PATCH v9 0/5] iommu: Support mappings/reservations in reserved-memory regions

[Thierry Reding <thierry.reding@gmail.com>]

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On Fri, Sep 23, 2022 at 02:35:52PM +0200, Thierry Reding wrote:
> From: Thierry Reding <treding@nvidia.com>
> 
> Hi,
> 
> This version has several fixes over the previous v8, which can be found
> here:
> 
>   https://lore.kernel.org/all/20220905170833.396892-1-thierry.reding@gmail.com/
> 
> An example is included in the DT bindings, but here is an extract of
> what I've used to test this:
> 
>         reserved-memory {
>                 #address-cells = <2>;
>                 #size-cells = <2>;
>                 ranges;
> 
>                 /*
>                  * Creates an identity mapping for the framebuffer that
>                  * the firmware has setup to scan out a bootsplash from.
>                  */
>                 fb: framebuffer@92cb2000 {
>                         reg = <0x0 0x92cb2000 0x0 0x00800000>;
>                         iommu-addresses = <&dc0 0x0 0x92cb2000 0x0 0x00800000>;
>                 };
> 
>                 /*
>                  * Creates a reservation in the IOVA space to prevent
>                  * any buffers from being mapped to that region. Note
>                  * that on Tegra the range is actually quite different
>                  * from this, but it would conflict with the display
>                  * driver that I tested this against, so this is just
>                  * a dummy region for testing.
>                  */
>                 adsp: reservation-adsp {
>                         iommu-addresses = <&dc0 0x0 0x90000000 0x0 0x00010000>;
>                 };
>         };
> 
>         host1x@50000000 {
>                 dc@54200000 {
>                         memory-region = <&fb>, <&adsp>;
>                 };
>         };
> 
> This is abbreviated a little to focus on the essentials. Note also that
> the ADSP reservation is not actually used on this device and the driver
> for this doesn't exist yet, but I wanted to include this variant for
> testing, because we'll want to use these bindings for the reservation
> use-case as well at some point.
> 
> I've also been able to make use of this binding and the IOMMU code in
> conjunction with the simple-framebuffer driver to hand over a display
> configuration set up by UEFI to the Linux kernel.
> 
> Janne has confirmed[0] this to be suitable for indirect mappings as
> well, though these patches don't implement that feature yet. Potential
> extensions to this have been discussed but are not yet included at this
> time to not further complicate things.
> 
> Thierry
> 
> [0]: https://lore.kernel.org/all/20220909144504.GA4024@jannau.net/
> 
> Navneet Kumar (1):
>   iommu/tegra-smmu: Support managed domains
> 
> Thierry Reding (4):
>   dt-bindings: reserved-memory: Document iommu-addresses
>   iommu: Implement of_iommu_get_resv_regions()
>   iommu: dma: Use of_iommu_get_resv_regions()
>   iommu/tegra-smmu: Add support for reserved regions
> 
>  .../reserved-memory/reserved-memory.yaml      |  70 ++++++++++++
>  drivers/iommu/dma-iommu.c                     |   3 +
>  drivers/iommu/of_iommu.c                      | 104 ++++++++++++++++++
>  drivers/iommu/tegra-smmu.c                    |  86 ++++++++++++---
>  include/linux/of_iommu.h                      |   8 ++
>  5 files changed, 254 insertions(+), 17 deletions(-)

Joerg, if there are no further concerns on this, can you pick this up
once v6.1-rc1 is released?

Thanks,
Thierry

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