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From:   Evan Green <evgreen@chromium.org>
Date:   Wed, 30 Jan 2019 10:30:00 -0800
Message-ID: <CAE=gft7TnvSDskOmeXp4Z-D45uwOfwyiJo0CYY=Q93NR0PvRnA@mail.gmail.com>
Subject: Re: [PATCH v5 09/20] iommu/mediatek: Refine protect memory definition
To:     Yong Wu <yong.wu@mediatek.com>
Cc:     Joerg Roedel <joro@8bytes.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Rob Herring <robh+dt@kernel.org>,
        Tomasz Figa <tfiga@google.com>,
        Will Deacon <will.deacon@arm.com>,
        linux-mediatek@lists.infradead.org, srv_heupstream@mediatek.com,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        linux-arm-kernel@lists.infradead.org,
        iommu@lists.linux-foundation.org, Arnd Bergmann <arnd@arndb.de>,
        yingjoe.chen@mediatek.com, youlin.pei@mediatek.com,
        Nicolas Boichat <drinkcat@chromium.org>
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On Mon, Dec 31, 2018 at 7:58 PM Yong Wu <yong.wu@mediatek.com> wrote:
>
> The protect memory setting is a little different in the different SoCs.
> In the register REG_MMU_CTRL_REG(0x110), the TF_PROT(translation fault
> protect) shift bit is normally 4 while it shift 5 bits only in the
> mt8173. This patch delete the complex MACRO and use a common if-else
> instead.
>
> Also, use "F_MMU_TF_PROT_TO_PROGRAM_ADDR" instead of the hard code(2)
> which means the M4U will output the dirty data to the programmed
> address that we allocated dynamically when translation fault occurs.
>
> Signed-off-by: Yong Wu <yong.wu@mediatek.com>
> ---
> @Nicalos, I don't put it in the plat_data since only the previous mt8173
> shift 5. As I know, the latest SoC always use the new setting like mt2712
> and mt8183. Thus, I think it is unnecessary to put it in plat_data and
> let all the latest SoC set it. Hence, I still keep "== mt8173" for this
> like the reg REG_MMU_CTRL_REG.
> ---
>  drivers/iommu/mtk_iommu.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> index eca1536..35a1263 100644
> --- a/drivers/iommu/mtk_iommu.c
> +++ b/drivers/iommu/mtk_iommu.c
> @@ -53,11 +53,7 @@
>
>  #define REG_MMU_CTRL_REG                       0x110
>  #define F_MMU_PREFETCH_RT_REPLACE_MOD          BIT(4)
> -#define F_MMU_TF_PROTECT_SEL_SHIFT(data) \
> -       ((data)->plat_data->m4u_plat == M4U_MT2712 ? 4 : 5)
> -/* It's named by F_MMU_TF_PROT_SEL in mt2712. */
> -#define F_MMU_TF_PROTECT_SEL(prot, data) \
> -       (((prot) & 0x3) << F_MMU_TF_PROTECT_SEL_SHIFT(data))
> +#define F_MMU_TF_PROT_TO_PROGRAM_ADDR          2
>
>  #define REG_MMU_IVRP_PADDR                     0x114
>
> @@ -521,9 +517,11 @@ static int mtk_iommu_hw_init(const struct mtk_iommu_data *data)
>                 return ret;
>         }
>
> -       regval = F_MMU_TF_PROTECT_SEL(2, data);
>         if (data->plat_data->m4u_plat == M4U_MT8173)
> -               regval |= F_MMU_PREFETCH_RT_REPLACE_MOD;
> +               regval = F_MMU_PREFETCH_RT_REPLACE_MOD |
> +                         (F_MMU_TF_PROT_TO_PROGRAM_ADDR << 5);
> +       else
> +               regval = F_MMU_TF_PROT_TO_PROGRAM_ADDR << 4;

I agree with Nicolas with regard to not having the random 4 and 5
sprinkled in the function.
-Evan