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From:   Chun-Kuang Hu <chunkuang.hu@kernel.org>
Date:   Tue, 4 Aug 2020 00:13:23 +0800
Message-ID: <CAAOTY_9UcnSDTaVPDPyPLsWEYcrcq5MY=z520MWtFdeLw_FqGQ@mail.gmail.com>
Subject: Re: [PATCH v4 2/2] soc: mediatek: add mtk-devapc driver
To:     Neal Liu <neal.liu@mediatek.com>
Cc:     Chun-Kuang Hu <chunkuang.hu@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        devicetree@vger.kernel.org,
        wsd_upstream <wsd_upstream@mediatek.com>,
        lkml <linux-kernel@vger.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@lists.infradead.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>
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Hi, Neal:

Neal Liu <neal.liu@mediatek.com> =E6=96=BC 2020=E5=B9=B48=E6=9C=883=E6=97=
=A5 =E9=80=B1=E4=B8=80 =E4=B8=8A=E5=8D=8811:32=E5=AF=AB=E9=81=93=EF=BC=9A
>
> Hi Chun-Kuang,
>
> On Fri, 2020-07-31 at 23:03 +0800, Chun-Kuang Hu wrote:
> > Hi, Neal:
> >
> > Neal Liu <neal.liu@mediatek.com> =E6=96=BC 2020=E5=B9=B47=E6=9C=8831=E6=
=97=A5 =E9=80=B1=E4=BA=94 =E4=B8=8A=E5=8D=8810:44=E5=AF=AB=E9=81=93=EF=BC=
=9A
> > >
> > > Hi Chun-Kuang,
> > >
> > >
> > > On Thu, 2020-07-30 at 00:38 +0800, Chun-Kuang Hu wrote:
> > > > Hi, Neal:
> > > >
> > > > Neal Liu <neal.liu@mediatek.com> =E6=96=BC 2020=E5=B9=B47=E6=9C=882=
9=E6=97=A5 =E9=80=B1=E4=B8=89 =E4=B8=8B=E5=8D=884:29=E5=AF=AB=E9=81=93=EF=
=BC=9A
> > > > >
> > > > > MediaTek bus fabric provides TrustZone security support and data
> > > > > protection to prevent slaves from being accessed by unexpected
> > > > > masters.
> > > > > The security violation is logged and sent to the processor for
> > > > > further analysis or countermeasures.
> > > > >
> > > > > Any occurrence of security violation would raise an interrupt, an=
d
> > > > > it will be handled by mtk-devapc driver. The violation
> > > > > information is printed in order to find the murderer.
> > > > >
> > > > > Signed-off-by: Neal Liu <neal.liu@mediatek.com>
> > > > > ---
> > > >
> > > > [snip]
> > > >
> > > > > +
> > > > > +/*
> > > > > + * devapc_extract_vio_dbg - extract full violation information a=
fter doing
> > > > > + *                          shift mechanism.
> > > > > + */
> > > > > +static void devapc_extract_vio_dbg(struct mtk_devapc_context *ct=
x)
> > > > > +{
> > > > > +       const struct mtk_devapc_vio_dbgs *vio_dbgs;
> > > > > +       struct mtk_devapc_vio_info *vio_info;
> > > > > +       void __iomem *vio_dbg0_reg;
> > > > > +       void __iomem *vio_dbg1_reg;
> > > > > +       u32 dbg0;
> > > > > +
> > > > > +       vio_dbg0_reg =3D ctx->devapc_pd_base + ctx->offset->vio_d=
bg0;
> > > > > +       vio_dbg1_reg =3D ctx->devapc_pd_base + ctx->offset->vio_d=
bg1;
> > > > > +
> > > > > +       vio_dbgs =3D ctx->vio_dbgs;
> > > > > +       vio_info =3D ctx->vio_info;
> > > > > +
> > > > > +       /* Starts to extract violation information */
> > > > > +       dbg0 =3D readl(vio_dbg0_reg);
> > > > > +       vio_info->vio_addr =3D readl(vio_dbg1_reg);
> > > > > +
> > > > > +       vio_info->master_id =3D (dbg0 & vio_dbgs->mstid.mask) >>
> > > > > +                             vio_dbgs->mstid.start;
> > > >
> > > > What is master_id? How could we use it to debug? For example, if we
> > > > get a master_id =3D 1, what should we do for this?
> > > >
> > > > > +       vio_info->domain_id =3D (dbg0 & vio_dbgs->dmnid.mask) >>
> > > > > +                             vio_dbgs->dmnid.start;
> > > >
> > > > What is domain_id? How could we use it to debug? For example, if we
> > > > get a domain_id =3D 2, what should we do for this?
> > > >
> > >
> > > master_id and domain_id belongs our bus side-band signal info. It can
> > > help us to find the violation master.
> >
> > Does 'violation master' means the hardware could access the protected
> > register? (ex. CPU, GCE, ...) If so, I think it's better to add
> > comment to explain how to map (master_id, domain_id) to a hardware
> > (maybe the device in device tree) because every body does not know
> > what the number means. Don't try to translate the number to a string
> > because this would cost much time to do this. Just print a number and
> > we could find out the master by the comment.
>
> 'violation master' means the master which violates the permission
> control. For example, if we set permission 'Secure R/W only' as CPU to
> spi register. When violation is triggered, it means CPU access spi
> register through normal world instead of secure world, which is not
> allowed.
>
> 'master_id' cannot use the simple comments to describe which master it
> is. It depends on violation slaves. For example, if there are two
> violations:
> 1. CPU access spi reg
> 2. CPU access timer reg
> It might be different 'master_id' for CPU on these two cases.
> I would prefer to remain the id number if translate to a string is a bad
> idea.
> Thanks !

It seams that master_id and domain_id does not help for debug. When we
get master_id =3D 1 and domain_id =3D 2, we don't know what it mean. I
think we just need violation address because we could find the driver
that write this address and the bug would be inside this driver. So
need not to process master_id and domain_id.

Regards,
Chun-Kuang.

>
> >
> > >
> > > > > +       vio_info->write =3D ((dbg0 & vio_dbgs->vio_w.mask) >>
> > > > > +                           vio_dbgs->vio_w.start) =3D=3D 1;
> > > > > +       vio_info->read =3D ((dbg0 & vio_dbgs->vio_r.mask) >>
> > > > > +                         vio_dbgs->vio_r.start) =3D=3D 1;
> > > > > +       vio_info->vio_addr_high =3D (dbg0 & vio_dbgs->addr_h.mask=
) >>
> > > > > +                                 vio_dbgs->addr_h.start;
> > > >
> > > > What is vio_addr_high? As I know all register address are 32 bits, =
is
> > > > vio_addr_high the address above 32 bits?
> > >
> > > Yes, you are right. In MT6779, all register base are 32 bits. We can
> > > ignore this info for current driver. I'll update on next patch.
> > > Thanks !
> >
> > Such a strange hardware, all register is 32 bits but it has a
> > vio_addr_high in its register. OK, just drop this.
> >
> > >
> > > >
> > > > > +
> > > > > +       devapc_vio_info_print(ctx);
> > > > > +}
> > > > > +
> > > >