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Subject: Re: [PATCH v6 21/22] iommu/mediatek: Fix iova_to_phys PA start for
 4GB mode
From:   Yong Wu <yong.wu@mediatek.com>
To:     Evan Green <evgreen@chromium.org>
CC:     <youlin.pei@mediatek.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
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        Will Deacon <will.deacon@arm.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Tomasz Figa <tfiga@google.com>,
        <iommu@lists.linux-foundation.org>,
        Rob Herring <robh+dt@kernel.org>,
        <linux-mediatek@lists.infradead.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        <yingjoe.chen@mediatek.com>, <anan.sun@mediatek.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Matthias Kaehlcke <mka@chromium.org>,
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Date:   Wed, 20 Feb 2019 17:17:15 +0800
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On Tue, 2019-02-19 at 15:33 -0800, Evan Green wrote:
> On Sun, Feb 17, 2019 at 1:09 AM Yong Wu <yong.wu@mediatek.com> wrote:
> >
> > In the 4GB mode, the physical address is remapped,
> >
> > Here is the detailed remap relationship.
> > CPU PA         ->    HW PA
> > 0x4000_0000          0x1_4000_0000 (Add bit32)
> > 0x8000_0000          0x1_8000_0000 ...
> > 0xc000_0000          0x1_c000_0000 ...
> > 0x1_0000_0000        0x1_0000_0000 (No change)
> >
> > Thus, we always add bit32 for PA when entering mtk_iommu_map.
> > But in the iova_to_phys, the CPU don't need this bit32 if the
> > PA is from 0x1_4000_0000 to 0x1_ffff_ffff.
> > This patch discards the bit32 in this iova_to_phys in the 4GB mode.
> >
> > Signed-off-by: Yong Wu <yong.wu@mediatek.com>
> > ---
> >  drivers/iommu/mtk_iommu.c | 18 ++++++++++++++++++
> >  1 file changed, 18 insertions(+)
> >
> > diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> > index 0277396..076d333 100644
> > --- a/drivers/iommu/mtk_iommu.c
> > +++ b/drivers/iommu/mtk_iommu.c
> > @@ -119,6 +119,19 @@ struct mtk_iommu_domain {
> >
> >  static const struct iommu_ops mtk_iommu_ops;
> >
> > +/*
> > + * In M4U 4GB mode, the physical address is remapped as below:
> > + *  CPU PA         ->   M4U HW PA
> > + *  0x4000_0000         0x1_4000_0000 (Add bit32)
> > + *  0x8000_0000         0x1_8000_0000 ...
> > + *  0xc000_0000         0x1_c000_0000 ...
> > + *  0x1_0000_0000       0x1_0000_0000 (No change)
> > + *
> > + * Thus, We always add BIT32 in the iommu_map and disable BIT32 if PA is >=
> > + * 0x1_4000_0000 in the iova_to_phys.
> > + */
> > +#define MTK_IOMMU_4GB_MODE_PA_140000000     0x140000000UL
> > +
> >  static LIST_HEAD(m4ulist);     /* List all the M4U HWs */
> >
> >  #define for_each_m4u(data)     list_for_each_entry(data, &m4ulist, list)
> > @@ -415,6 +428,7 @@ static phys_addr_t mtk_iommu_iova_to_phys(struct iommu_domain *domain,
> >                                           dma_addr_t iova)
> >  {
> >         struct mtk_iommu_domain *dom = to_mtk_domain(domain);
> > +       struct mtk_iommu_data *data = mtk_iommu_get_m4u_data();
> >         unsigned long flags;
> >         phys_addr_t pa;
> >
> > @@ -422,6 +436,10 @@ static phys_addr_t mtk_iommu_iova_to_phys(struct iommu_domain *domain,
> >         pa = dom->iop->iova_to_phys(dom->iop, iova);
> >         spin_unlock_irqrestore(&dom->pgtlock, flags);
> >
> > +       if (data->plat_data->has_4gb_mode && data->dram_is_4gb &&
> > +           pa >= MTK_IOMMU_4GB_MODE_PA_140000000)
> > +               pa &= ~BIT_ULL(32);
> > +
> 
> The define doesn't really make it much better, but I guess it doesn't
> make it worse either. As I was reviewing this I was thinking that this
> should be rolled into patch 6 "iommu/io-pgtable-arm-v7s: Extend
> MediaTek 4GB Mode". But I guess this was returning bad PAs since
> before this series, right? So does this need a Fixes tag?

Thanks very much for your reviewing so many patches.

Yes. The issue exist before this series, It was introduced by this
commit:
30e2fccf9512 ("iommu/mediatek: Enlarge the validate PA range for 4GB
mode")

I will send a new version to add this tag.

> -Evan
> 
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