Re: [RFC PATCH 07/11] arm64: dts: qcom: hamoa: Move Iris IOMMUs to sub nodes

[Dmitry Baryshkov]

On Fri, Jul 10, 2026 at 11:46:58PM +0100, Bryan O'Donoghue wrote:
> On 09/07/2026 13:35, Vikash Garodia wrote:
> > The Iris VPU has separate streams with different IOVA constraints. The
> > non-pixel stream must be limited to the 0-600 MB IOVA range, while the
> > pixel stream can use the full IOVA space.
> 
> 
> > Using a single set of IOMMU entries for the Iris node does not describe
> > these per-stream limits and can allow accesses outside the supported
> > range, which may lead to device crashes. One such issue was reported at:
> > https://gitlab.freedesktop.org/drm/msm/-/work_items/100
> > 
> > Add non-pixel and pixel child nodes, move each stream ID to its
> > corresponding child node, and add a reserved IOVA range for the
> > non-pixel stream.
> > 
> > Co-developed-by: Vishnu Reddy <busanna.reddy@xxxxxxxxxxxxxxxx>
> > Signed-off-by: Vishnu Reddy <busanna.reddy@xxxxxxxxxxxxxxxx>
> > Signed-off-by: Vikash Garodia <vikash.garodia@xxxxxxxxxxxxxxxx>
> The thing of it is, this _is_ a bugfix - perhaps its not one that can be
> backported, actually scratch that, this isn't possible to land in -stable
> realistically.
> 
> So what is needed here is a strategy for fixing -stable.

I think, we need to start with defining, which platforms are affected.
sm8150+? SM8250+? SDM845+? MSM8996+?

> 
> That could be apply Daniel's patch and backport it with Fixes: - with
> mainline then say applying this change and reverting Daniel's patch
> 
> or
> 
> That could mean some other solution for -stable - up for debate - what's not
> up for debate is this series needs to _address_ what happens to stable for
> all of the target platforms - and then transition mainline to the new and
> shiny way.
> 
> That could mean
> 
> - Applying Daniel's fix with Fixes: and cc-stable
> - That patch needs to be extended to _each_ Iris platform containing
>   this bug... all of them I think.
> - Updating bindings
> - Updating DT with new method simultaneously reverting Daniel's fix
> 
> And I do mean doing that in one progressive series - a fixup for mainline
> alone isn't enough.

-- 
With best wishes
Dmitry