Re: [PATCH v3 06/20] iommu/mtk: Remove detach_dev callback

[Baolu Lu]

On 11/28/22 9:59 PM, Robin Murphy wrote:
> On 2022-11-28 13:49, Jason Gunthorpe wrote:
> > On Mon, Nov 28, 2022 at 02:46:34PM +0800, Lu Baolu wrote:
> > > The IOMMU driver supports default domain, so the detach_dev op will 
> > > never
> > > be called. Remove it to avoid dead code.
> > >
> > > Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> > > ---
> > >   drivers/iommu/mtk_iommu.c | 9 ---------
> > >   1 file changed, 9 deletions(-)
> >
> > I listed this driver as not supporting default domains:
> >
> > https://lore.kernel.org/linux-iommu/20220516135741.GV1343366@xxxxxxxxxx/
> >
> > ?
> >
> > Has something changed? Did I get it wrong?
>
> static struct iommu_domain *mtk_iommu_domain_alloc(unsigned type)
> {
>      struct mtk_iommu_domain *dom;
>
>      if (type != IOMMU_DOMAIN_DMA && type != IOMMU_DOMAIN_UNMANAGED)
>          return NULL;
> ...
>
>
> This one runs on arm64, so has always supported default domains for 
> iommu-dma to work.

This, together with several other ones, only support IOMMU_DOMAIN_DMA
type of default domain. The iommu core handle this by falling back to
IOMMU_DOMAIN_DMA if other types fail.

        dom = __iommu_domain_alloc(bus, type);
        if (!dom && type != IOMMU_DOMAIN_DMA) {
                dom = __iommu_domain_alloc(bus, IOMMU_DOMAIN_DMA);
                if (dom)
                        pr_warn("Failed to allocate default IOMMU 
domain of type %u for group %s - Falling back to IOMMU_DOMAIN_DMA",
                                type, group->name);
        }

I have another cleanup series:

https://github.com/LuBaolu/intel-iommu/commits/iommu-use-def_default_type-wip

which adds IOMMU_DOMAIN_DMA default domain type requirement in the
def_domain_type callback. I planed to bring that to discussion after
this one.

Best regards,
baolu