linux-kernel - Re: [PATCH v4 2/2] soc: mediatek: add mtk-devapc driver

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Date:   Fri, 31 Jul 2020 10:52:50 +0800
From:   Neal Liu <neal.liu@...iatek.com>
To:     Chun-Kuang Hu <chunkuang.hu@...nel.org>
CC:     Neal Liu <neal.liu@...iatek.com>, Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        <devicetree@...r.kernel.org>,
        wsd_upstream <wsd_upstream@...iatek.com>,
        lkml <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 2/2] soc: mediatek: add mtk-devapc driver

Hi Chun-Kuang,

On Fri, 2020-07-31 at 00:14 +0800, Chun-Kuang Hu wrote:
> Hi, Neal:
> 
> Neal Liu <neal.liu@...iatek.com> 於 2020年7月29日 週三 下午4:29寫道：
> >
> > 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, and
> > 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@...iatek.com>
> > ---
> 
> [snip]
> 
> > +
> > +/*
> > + * devapc_extract_vio_dbg - extract full violation information after doing
> > + *                          shift mechanism.
> > + */
> > +static void devapc_extract_vio_dbg(struct mtk_devapc_context *ctx)
> > +{
> > +       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 = ctx->devapc_pd_base + ctx->offset->vio_dbg0;
> > +       vio_dbg1_reg = ctx->devapc_pd_base + ctx->offset->vio_dbg1;
> > +
> > +       vio_dbgs = ctx->vio_dbgs;
> > +       vio_info = ctx->vio_info;
> > +
> > +       /* Starts to extract violation information */
> > +       dbg0 = readl(vio_dbg0_reg);
> > +       vio_info->vio_addr = readl(vio_dbg1_reg);
> > +
> > +       vio_info->master_id = (dbg0 & vio_dbgs->mstid.mask) >>
> > +                             vio_dbgs->mstid.start;
> > +       vio_info->domain_id = (dbg0 & vio_dbgs->dmnid.mask) >>
> > +                             vio_dbgs->dmnid.start;
> > +       vio_info->write = ((dbg0 & vio_dbgs->vio_w.mask) >>
> > +                           vio_dbgs->vio_w.start) == 1;
> > +       vio_info->read = ((dbg0 & vio_dbgs->vio_r.mask) >>
> > +                         vio_dbgs->vio_r.start) == 1;
> > +       vio_info->vio_addr_high = (dbg0 & vio_dbgs->addr_h.mask) >>
> > +                                 vio_dbgs->addr_h.start;
> 
> 
> I would like to define the type of ctx->vio_info to be
> 
> struct mtk_devapc_vio_dbgs {
>     u32 mstid:16;
>     u32 dmnid:6;
>     u32 vio_w:1;
>     u32 vio_r:1;
>     u32 addr_h:4;
>     u32 resv:4;
> };
> 
> so the code would like the simple way
> 
> ctx->vio_info = (struct mtk_devapc_vio_dbgs)readl(vio_dbg1_reg);
> 

This idea looks great! Is there any possible to pass the bit layout by
DT data, and still make this operation simple?
Why am I asking this question is because this bit layout is platform
dependent.

> Regards,
> Chun-Kuang.
> 
> > +
> > +       devapc_vio_info_print(ctx);
> > +}
> > +