Re: [PATCH v16 3/3] of: Respect #{iommu,msi}-cells in maps

[Neil Armstrong]

On 7/28/26 13:34, Dmitry Baryshkov wrote:
> On Thu, Jul 23, 2026 at 03:17:24PM +0200, Neil Armstrong wrote:
> > Hi,
> >
> > On 6/3/26 09:13, Vijayanand Jitta wrote:
> > > From: Robin Murphy <robin.murphy@xxxxxxx>
> > >
> > > So far our parsing of {iommu,msi}-map properties has always blindly
> > > assumed that the output specifiers will always have exactly 1 cell.
> > > This typically does happen to be the case, but is not actually enforced
> > > (and the PCI msi-map binding even explicitly states support for 0 or 1
> > > cells) - as a result we've now ended up with dodgy DTs out in the field
> > > which depend on this behaviour to map a 1-cell specifier for a 2-cell
> > > provider, despite that being bogus per the bindings themselves.
> > >
> > > Since there is some potential use in being able to map at least single
> > > input IDs to multi-cell output specifiers (and properly support 0-cell
> > > outputs as well), add support for properly parsing and using the target
> > > nodes' #cells values, albeit with the unfortunate complication of still
> > > having to work around expectations of the old behaviour too.
> > >
> > > Since there are multi-cell output specifiers, the callers of of_map_id()
> > > may need to get the exact cell output value for further processing.
> > > Update of_map_id() to set args_count in the output to reflect the actual
> > > number of output specifier cells.
> > >
> > > Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
> > > Signed-off-by: Charan Teja Kalla <charan.kalla@xxxxxxxxxxxxxxxx>
> > > Signed-off-by: Vijayanand Jitta <vijayanand.jitta@xxxxxxxxxxxxxxxx>
> > > ---
> > >    drivers/of/base.c  | 168 +++++++++++++++++++++++++++++++++++++++++------------
> > >    include/linux/of.h |   6 +-
> > >    2 files changed, 135 insertions(+), 39 deletions(-)
> > >
> > > diff --git a/drivers/of/base.c b/drivers/of/base.c
> > > index d658c2620135..ac7961cbab94 100644
> > > --- a/drivers/of/base.c
> > > +++ b/drivers/of/base.c
> > > @@ -2116,19 +2116,49 @@ int of_find_last_cache_level(unsigned int cpu)
> > >    	return cache_level;
> > >    }
> > > +/*
> > > + * Some DTs have an iommu-map targeting a 2-cell IOMMU node while
> > > + * specifying only 1 cell. Fortunately they all consist of value '1'
> > > + * as the 2nd cell entry with the same target, so check for that pattern.
> > > + *
> > > + * Example:
> > > + *	IOMMU node:
> > > + *		#iommu-cells = <2>;
> > > + *
> > > + *	Device node:
> > > + *		iommu-map = <0x0000 &smmu 0x0000 0x1>,
> > > + *			    <0x0100 &smmu 0x0100 0x1>;
> >
> > So the sm8650 PCIe controllers has:
> >
> > pcie@1c08000:
> > 			iommu-map = <0     &apps_smmu 0x1480 0x1>,
> > 				    <0x100 &apps_smmu 0x1481 0x1>;
>
> To silence the warning, update the iommu maps to:
>
> 			iommu-map = <0     &apps_smmu 0x1480 0x0 0x1>,
> 				    <0x100 &apps_smmu 0x1481 0x0 0x1>;

Will do, I was surprised none of the DT were fixed.

Thanks,
Neil