Re: [PATCH v9 3/3] iommu/mediatek: Allow page table PA up to 35bit

From: yf.wang
Date: Thu Jun 16 2022 - 03:59:52 EST


On Wed, 2022-06-15 at 18:25 +0100, Robin Murphy wrote:
> On 2022-06-15 17:12, yf.wang--- via iommu wrote:
> > From: Yunfei Wang <yf.wang@xxxxxxxxxxxx>
> >
> > Single memory zone feature will remove ZONE_DMA32 and ZONE_DMA. So
> > add
> > the quirk IO_PGTABLE_QUIRK_ARM_MTK_TTBR_EXT to let level 1 and
> > level 2
> > pgtable support at most 35bit PA.
>
> I'm not sure how this works in practice, given that you don't seem to
> be
> setting the IOMMU's own DMA masks to more than 32 bits, so the DMA
> mapping in io-pgtable is going to fail if you ever do actually
> allocate
> a pagetable page above 4GB :/
>

Hi Robin,
About DMA masks, the master device has set dma mask, when iommu do dma map,
it will check the dam_mask of the master dev to determine which range the
address of the iova alloc is in.

Add the quirk ARM_MTK_TTBR_EXT to let pgtable support larger phys memory.
Do actually test work fine, example:
pgtable phys address:0x12054006a, encoded to 32 bits ttbr:0x20540001


> > Signed-off-by: Ning Li <ning.li@xxxxxxxxxxxx>
> > Signed-off-by: Yunfei Wang <yf.wang@xxxxxxxxxxxx>
> > ---
> > drivers/iommu/mtk_iommu.c | 14 +++++++++-----
> > 1 file changed, 9 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> > index 3d62399e8865..4dbc33758711 100644
> > --- a/drivers/iommu/mtk_iommu.c
> > +++ b/drivers/iommu/mtk_iommu.c
> > @@ -138,6 +138,7 @@
> > /* PM and clock always on. e.g. infra iommu */
> > #define PM_CLK_AO BIT(15)
> > #define IFA_IOMMU_PCIE_SUPPORT BIT(16)
> > +#define PGTABLE_PA_35_EN BIT(17)
> >
> > #define MTK_IOMMU_HAS_FLAG_MASK(pdata, _x, mask) \
> > ((((pdata)->flags) & (mask)) == (_x))
> > @@ -240,6 +241,7 @@ struct mtk_iommu_data {
> > struct mtk_iommu_domain {
> > struct io_pgtable_cfg cfg;
> > struct io_pgtable_ops *iop;
> > + u32 ttbr;
> >
> > struct mtk_iommu_bank_data *bank;
> > struct iommu_domain domain;
> > @@ -596,6 +598,9 @@ static int mtk_iommu_domain_finalise(struct
> > mtk_iommu_domain *dom,
> > .iommu_dev = data->dev,
> > };
> >
> > + if (MTK_IOMMU_HAS_FLAG(data->plat_data, PGTABLE_PA_35_EN))
> > + dom->cfg.quirks |= IO_PGTABLE_QUIRK_ARM_MTK_TTBR_EXT;
> > +
> > if (MTK_IOMMU_HAS_FLAG(data->plat_data, HAS_4GB_MODE))
> > dom->cfg.oas = data->enable_4GB ? 33 : 32;
> > else
> > @@ -684,8 +689,8 @@ static int mtk_iommu_attach_device(struct
> > iommu_domain *domain,
> > goto err_unlock;
> > }
> > bank->m4u_dom = dom;
> > - writel(dom->cfg.arm_v7s_cfg.ttbr & MMU_PT_ADDR_MASK,
> > - bank->base + REG_MMU_PT_BASE_ADDR);
> > + bank->m4u_dom->ttbr = MTK_IOMMU_ADDR(dom-
> > >cfg.arm_v7s_cfg.ttbr);
> > + writel(bank->m4u_dom->ttbr, data->base +
> > REG_MMU_PT_BASE_ADDR);
>
> To add to my comment on patch #1, having to make this change here
> further indicates that you're using it the wrong way.
>
> Thanks,
> Robin.
>

Hi Robin,
According to your Path#1's suggestion, next version will keep ttbr to encoded 32 bits,
then will don't need to modify it.

Thanks,
Yunfei.