Re: [PATCH 2/2] iommu: mtk_iommu: Add support for MT6795 Helio X10 M4Us

[Matthias Brugger]

On 17/05/2022 11:26, AngeloGioacchino Del Regno wrote:
> Il 17/05/22 11:08, Yong Wu ha scritto:
> > On Fri, 2022-05-13 at 17:14 +0200, AngeloGioacchino Del Regno wrote:
> > > Add support for the M4Us found in the MT6795 Helio X10 SoC.
> > >
> > > Signed-off-by: AngeloGioacchino Del Regno <
> > > angelogioacchino.delregno@xxxxxxxxxxxxx>
> > > ---
> > >   drivers/iommu/mtk_iommu.c | 20 +++++++++++++++++++-
> > >   1 file changed, 19 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> > > index 71b2ace74cd6..3d802dd3f377 100644
> > > --- a/drivers/iommu/mtk_iommu.c
> > > +++ b/drivers/iommu/mtk_iommu.c
> > > @@ -157,6 +157,7 @@
> > >   enum mtk_iommu_plat {
> > >       M4U_MT2712,
> > >       M4U_MT6779,
> > > +    M4U_MT6795,
> > >       M4U_MT8167,
> > >       M4U_MT8173,
> > >       M4U_MT8183,
> > > @@ -953,7 +954,8 @@ static int mtk_iommu_hw_init(const struct
> > > mtk_iommu_data *data, unsigned int ban
> > >        * Global control settings are in bank0. May re-init these
> > > global registers
> > >        * since no sure if there is bank0 consumers.
> > >        */
> > > -    if (data->plat_data->m4u_plat == M4U_MT8173) {
> > > +    if (data->plat_data->m4u_plat == M4U_MT6795 ||
> > > +        data->plat_data->m4u_plat == M4U_MT8173) {
> > >           regval = F_MMU_PREFETCH_RT_REPLACE_MOD |
> > >                F_MMU_TF_PROT_TO_PROGRAM_ADDR_MT8173;
> > >       } else {
> > > @@ -1138,6 +1140,9 @@ static int mtk_iommu_probe(struct
> > > platform_device *pdev)
> > >           case M4U_MT2712:
> > >               p = "mediatek,mt2712-infracfg";
> > >               break;
> > > +        case M4U_MT6795:
> > > +            p = "mediatek,mt6795-infracfg";
> > > +            break;
> > >           case M4U_MT8173:
> > >               p = "mediatek,mt8173-infracfg";
> > >               break;
> > > @@ -1404,6 +1409,18 @@ static const struct mtk_iommu_plat_data
> > > mt6779_data = {
> > >       .larbid_remap  = {{0}, {1}, {2}, {3}, {5}, {7, 8}, {10}, {9}},
> > >   };
> > > +static const struct mtk_iommu_plat_data mt6795_data = {
> > > +    .m4u_plat     = M4U_MT6795,
> > > +    .flags          = HAS_4GB_MODE | HAS_BCLK | RESET_AXI |
> > > +            HAS_LEGACY_IVRP_PADDR | MTK_IOMMU_TYPE_MM,
> > > +    .inv_sel_reg  = REG_MMU_INV_SEL_GEN1,
> > > +    .banks_num    = 1,
> > > +    .banks_enable = {true},
> > > +    .iova_region  = single_domain,
> > > +    .iova_region_nr = ARRAY_SIZE(single_domain),
> > > +    .larbid_remap = {{0}, {1}, {2}, {3}, {4}}, /* Linear mapping.
> > > */
> > > +};
> >
> > This is nearly same with mt8173_data. mt8173 has one more larb than
> > mt6795, its larbid_remap is also ok for mt6795.
>
> I think that we should be explicit about the larbid_remap property,
> since mt6795 has one less larb, we should explicitly say that like
> I did there... that's only for human readability I admit ... but,
> still, I wouldn't want to see people thinking that MT6795 has 6 LARBs
> because they've read that larbid_remap having 6 entries.
>
> > thus it looks we could use mt8173 as the backward compatible.
> >      compatible = "mediatek,mt6795-m4u",
> >                   "mediatek,mt8173-m4u";
> >
> > After this, the only thing is about "mediatek,mt6795-infracfg". we have
> > to try again with mediatek,mt6795-infracfg after mediatek,mt8173-
> > infracfg fail. I think we should allow the backward case in 4GB mode
> > judgment if we have.
> >
> > What's your opinion? or some other suggestion?
> > Thanks.
>
> I know, I may have a plan for that, but I wanted to have a good reason to
> propose such a thing, as if it's just about two SoCs needing that, there
> would be no good reason to get things done differently.
>
> ...so, in order to provide a good cleanup, we have two possible roads to
> follow here: either we add a generic "mediatek,infracfg" compatible to the
> infra node (but I don't like that), or we can do it like it was previously
> done in mtk-pm-domains.c (I prefer that approach):
>
> iommu: iommu@somewhere {
>      ... something ...
>      mediatek,infracfg = <&infracfg>;
> };
>
> infracfg = syscon_regmap_lookup_by_compatible(node, "mediatek,infracfg");
> if (IS_ERR(infracfg)) {
>      /* try with the older way */
>      switch (...) {
>      case .... p = "mediatek,mt2712-infracfg";
>      ... blah blah ...
>      }
>      /* legacy also failed, ouch! */
>      if (IS_ERR(infracfg))
>          return PTR_ERR(infracfg);
> }
>
> ret = regmap_read ... etc etc etc

I prefer that approach as well.

Regards,
Matthias

> Cheers,
> Angelo