[PATCH RFC 03/13] drm/msm: look for lpac from dts

[Dmitry Baryshkov]

On Tue, Jul 07, 2026 at 05:02:43PM +0200, Anna Maniscalco wrote:
> On 7/6/26 5:04 PM, Dmitry Baryshkov wrote:
> > On Sun, Jul 05, 2026 at 09:13:37PM +0200, Anna Maniscalco wrote:
> > > In order to associate the SID used by LPAC to it's own domain and
> > > context bank we need a separate node on the DTS.
> > Can we use iommu-map instead of adding a new device using the same
> > addresses? You provide zero explanations, but it seems like you are
> > trying to separate a part of the GPU into a separate device, but it's
> > unnecessary.
> 
> What I was trying to say is that we need to map sid0 and sid1 to different
> context banks.
> 
> From what I recall, so long as we use the same dt node, the iommu drivert
> provides no way of doing this.
> 
> What kgsl does is having a node for the iommu and then subnodes for gfx lpac
> and secure.
> 
> The address on the lpac device doesn't really matter. I have very limted
> knowledge of DTSs but I think we could just leave it out altogether?

I think, you were poined to the Glymur Iris patches. Another option is
the QDA driver being submitted too. Both ot them use iommu-map to
describe the same usecase - a set of SIDs which are used by the device
but which should not be a part of the defaut set. With it in place you
don't need to have separate qcom,lpac devices, no additional properties,
etc. 

I'd recommend following the same approach.

> 
> > 
> > > Add the code to look up that node on initialization.
> > > 
> > > Signed-off-by: Anna Maniscalco <anna.maniscalco2000 at gmail.com>
> > > ---
> > >   drivers/gpu/drm/msm/adreno/adreno_gpu.c | 21 ++++++++++++++++++++-
> > >   drivers/gpu/drm/msm/msm_gpu.h           |  1 +
> > >   2 files changed, 21 insertions(+), 1 deletion(-)
> > > 
> 
> Best regards,
> -- 
> Anna Maniscalco <anna.maniscalco2000 at gmail.com>
> 

-- 
With best wishes
Dmitry