Re: [PATCH 2/3] iommu: mediatek: Add support of unmanaged iommu domain

[Alexandre Bailon]

Hi Robin

On 1/30/23 13:04, Robin Murphy wrote:
> On 2023-01-30 10:27, Alexandre Bailon wrote:
> > Currently, the driver can allocate an unmanaged iommu domain.
> > But, this only works for SoC having multiple bank or multiple iova 
> > region.
>
> That is for good reason - there is only a single pagetable per bank, so 
> if there are multiple devices assigned to a single bank, they cannot 
> possibly be attached to different domains at the same time. Hence why 
> the banks are modelled as groups.
I understand.
I am trying to upstream a remoteproc driver but the remote processor is
behind the iommu.
remoteproc can manage the iommu but it requires an unmanaged domain.
I tried a couple of things but this cause code duplication,
implies many hacks and not always reliable.
Do you have any suggestion ?

Thanks,
Alexandre
> Thanks,
> Robin.
>
> > This updates the driver to also support unmanaged iommu domain if
> > MTK_UNMANAGED_DEVICE is set in the iommu id.
> >
> > Signed-off-by: Alexandre Bailon <abailon@xxxxxxxxxxxx>
> > ---
> >   drivers/iommu/mtk_iommu.c | 6 ++++++
> >   1 file changed, 6 insertions(+)
> >
> > diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> > index 2badd6acfb23d..5884a1ad409a0 100644
> > --- a/drivers/iommu/mtk_iommu.c
> > +++ b/drivers/iommu/mtk_iommu.c
> > @@ -858,9 +858,15 @@ static int mtk_iommu_get_group_id(struct device 
> > *dev, const struct mtk_iommu_pla
> >   static struct iommu_group *mtk_iommu_device_group(struct device *dev)
> >   {
> >       struct mtk_iommu_data *c_data = dev_iommu_priv_get(dev), *data;
> > +    struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
> >       struct list_head *hw_list = c_data->hw_list;
> >       struct iommu_group *group;
> >       int groupid;
> > +    int i;
> > +
> > +    for (i = 0; i < fwspec->num_ids; i++)
> > +        if (MTK_M4U_UNMANAGED(fwspec->ids[i]))
> > +            return iommu_group_alloc();
> >       data = mtk_iommu_get_frst_data(hw_list);
> >       if (!data)