Re: [PATCH v3 1/6] dt-bindings: iommu: arm,smmu: Document interconnects property

[Dmitry Baryshkov]

On Mon, Jul 20, 2026 at 07:41:35PM +0530, Bibek Kumar Patro wrote:
> 
> 
> On 7/8/2026 8:48 PM, Bjorn Andersson wrote:
> > On Wed, Jul 08, 2026 at 08:22:00PM +0530, Bibek Kumar Patro wrote:
> > > 
> > > 
> > > On 7/7/2026 10:12 PM, Dmitry Baryshkov wrote:
> > > > On Tue, Jul 07, 2026 at 06:06:59PM +0530, Bibek Kumar Patro wrote:
> > > > > 
> > > > > 
> > > > > On 7/6/2026 11:09 PM, Dmitry Baryshkov wrote:
> > > > > > On Mon, Jul 06, 2026 at 10:26:34PM +0530, Bibek Kumar Patro wrote:
> > > > > > > Some SoC implementations require a bandwidth vote on an interconnect
> > > > > > > path before the SMMU register space is accessible. Add the optional
> > > > > > 
> > > > > > Why is it limited only to those SoCs? Is it also applicable to other
> > > > > > Qualcomm SoCs?
> > > > > > 
> > > > > 
> > > > > I was hoping to keep this series focused on the core infrastructure
> > > > > changes: the bindings, base ICC bandwidth-voting support, and DT
> > > > > interconnect properties for the platforms currently supported on
> > > > > Qualcomm Linux and have been validated so far.
> > > > > 
> > > > > The additional targets have not been tested yet, so I'd prefer
> > > > > to add their support in a separate follow-up series once validation
> > > > > is complete, rather than growing this series further. WDYT?
> > > > 
> > > > Then it should be a part of the commit message. All SoCs since SDM12345
> > > > need to vote on the interconnect (and then, in the cover letter mention
> > > > that you convert only a few of the SoCs). We possibly can help with
> > > > testing on other platforms.
> > > > 
> > > 
> > > Ack, sounds reasonable.
> > > I'll add the first platform onwards which interconnect voting is required in
> > > commit description.
> > 
> > But to what degree is this related to a specific set of platforms? If we
> > look ahead, aren't we expecting the list to grow to include all
> > platforms in the end - resulting in a lot of noise and churn.
> > 
> 
> We have seen this issue consistently on SM8750 and later platforms, along
> with at least one customer-reported instance on SM8550. As a result,
> downstream Android implementations already vote for the required
> interconnect bandwidth explicitly on these platforms.
> 
> On Qualcomm Linux targets, we have observed similar issues on Kodiak, with a
> few occurrences on Talos as well.
> 
> My understanding is that the interconnects property remains optional, but in
> practice it is needed for Adreno SMMU operation on these platforms.

So, it goes back to Kodiak and Talos. What about SM8150? SDM845? Earlier
platforms? Is it limited to MMU-500? A6xx+?

-- 
With best wishes
Dmitry