Re: [PATCH] iommu/arm-smmu-qcom: Only enable stall on smmu-v2

[Robin Murphy]

On 2024-12-19 11:30 am, Will Deacon wrote:
> On Mon, Dec 16, 2024 at 09:10:17AM -0800, Rob Clark wrote:
> > From: Rob Clark <robdclark@xxxxxxxxxxxx>
> >
> > On mmu-500, stall-on-fault seems to stall all context banks, causing the
> > GMU to misbehave.  So limit this feature to smmu-v2 for now.
>
> MMU-500 has public documentation so please can you dig up what the
> actual behaviour is rather than guess?

Yeah, I'm pretty sure that's not true as stated, especially with 
SCTLR.HUPCF set as qcom_adreno_smmu_write_sctlr() does. However it is 
plausible that at the system interconnect level, a sufficient number of 
stalled transactions might backpressure other transactions from entering 
the same TBU, even if they are destined for a different context. That's 
more about the configuration and integration of individual SoCs than the 
SMMU IP used.

Robin.

> > This fixes an issue with an older mesa bug taking outo the system
> > because of GMU going off into the year.
>
> Sorry, but I don't understand this sentence.
>
> Will