lkml.org 
[lkml]   [2018]   [Sep]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH 0/5] Qcom smmu-500 TLB invalidation errata for sdm845
On Wed, Sep 5, 2018 at 5:22 AM Vivek Gautam <vivek.gautam@codeaurora.org> wrote:
>
>
> On 8/14/2018 5:54 PM, Vivek Gautam wrote:
> > Hi Will,
> >
> >
> > On 8/14/2018 5:10 PM, Will Deacon wrote:
> >> Hi Vivek,
> >>
> >> On Tue, Aug 14, 2018 at 04:25:23PM +0530, Vivek Gautam wrote:
> >>> Qcom's implementation of arm,mmu-500 on sdm845 has a
> >>> functional/performance
> >>> errata [1] because of which the TCU cache look ups are stalled during
> >>> invalidation cycle. This is mitigated by serializing all the
> >>> invalidation
> >>> requests coming to the smmu.
> >> How does this implementation differ from the one supported by
> >> qcom_iommu.c?
> >> I notice you're adding firmware hooks here, which we avoided by
> >> having the
> >> extra driver. Please help me understand which devices exist, how they
> >> differ, and which drivers are intended to support them!
> >
> > IIRC, the qcom_iommu driver was intended to support the static context
> > bank - SID
> > mapping, and is very specific to the smmu-v2 version present on
> > msm8916 soc.
> > However, this is the qcom's mmu-500 implementation specific errata.
> > qcom_iommu
> > will not be able to support mmu-500 configurations.
> > Rob Clark can add more.
> > Let you know what you suggest.
>
> Rob, can you please comment about how qcom-smmu driver has different
> implementation
> from arm-smmu driver?

sorry, I missed this thread earlier. But yeah, as you mentioned, the
purpose for qcom_iommu.c was to deal with the static context/SID
mapping.

(I guess it is all just software, and we could make qcom_iommu.c
support dynamic mapping as well, but I think then it starts to
duplicate most of arm_smmu.c, so that doesn't seem like the right
direction)

BR,
-R

> Will, in case we would want to use arm-smmu driver, what would you
> suggest for
> having the firmware hooks?
> Thanks.
>
> Best regards
> Vivek

\
 
 \ /
  Last update: 2018-09-05 12:05    [W:0.136 / U:0.500 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site