Re: [PATCH v2 2/2] soc: mediatek: devapc: add devapc-mt6873 driver

[Neal Liu <neal.liu@mediatek.com>]

Hi Chun-Kuang,


On Thu, 2020-06-25 at 14:19 +0800, Chun-Kuang Hu wrote:
> Hi, Neal:
> 
> Neal Liu <neal.liu@mediatek.com> 於 2020年6月19日 週五 下午6:01寫道：
> >
> > MT6873 bus frabric provides TrustZone security support and data
> > protection to prevent slaves from being accessed by unexpected
> > masters.
> > The security violations are 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 devapc-mt6873 driver. The violation
> > information is printed in order to find the murderer.
> >
> > Signed-off-by: Neal Liu <neal.liu@mediatek.com>
> > ---
> 
> [snip]
> 
> > +
> > +/*
> > + * sramrom_vio_handler - clean sramrom violation & print violation information
> > + *                      for debugging.
> > + */
> > +static void sramrom_vio_handler(struct mtk_devapc_context *devapc_ctx)
> > +{
> > +       const struct mtk_sramrom_sec_vio_desc *sramrom_vios;
> > +       struct mtk_devapc_vio_info *vio_info;
> > +       struct arm_smccc_res res;
> > +       size_t sramrom_vio_sta;
> > +       int sramrom_vio;
> > +       u32 rw;
> > +
> > +       sramrom_vios = devapc_ctx->soc->sramrom_sec_vios;
> > +       vio_info = devapc_ctx->soc->vio_info;
> > +
> > +       arm_smccc_smc(MTK_SIP_KERNEL_CLR_SRAMROM_VIO,
> > +                     0, 0, 0, 0, 0, 0, 0, &res);
> > +
> 
> This irq handler call arm_smccc_smc() to get into TrustZone, why not
> let the whole irq handler in TrustZone?
> 

I just replied to Matthias, let me try to explain it again.
There is no reason that it should be handed in TrustZone only. And it
has no security issue to handle it from Normal World.

But this functionality is not basic for devapc-mt6873 driver, I'll make
it as another patch.

> Regards,
> Chun-Kuang.
> 
> > +       sramrom_vio = res.a0;
> > +       sramrom_vio_sta = res.a1;
> > +       vio_info->vio_addr = res.a2;
> > +
> > +       if (sramrom_vio == SRAM_VIOLATION)
> > +               pr_info(PFX "SRAM violation is triggered\n");
> > +       else if (sramrom_vio == ROM_VIOLATION)
> > +               pr_info(PFX "ROM violation is triggered\n");
> > +       else
> > +               return;
> > +
> > +       vio_info->master_id = (sramrom_vio_sta & sramrom_vios->vio_id_mask)
> > +                       >> sramrom_vios->vio_id_shift;
> > +       vio_info->domain_id = (sramrom_vio_sta & sramrom_vios->vio_domain_mask)
> > +                       >> sramrom_vios->vio_domain_shift;
> > +       rw = (sramrom_vio_sta & sramrom_vios->vio_rw_mask) >>
> > +                       sramrom_vios->vio_rw_shift;
> > +
> > +       if (rw)
> > +               vio_info->write = 1;
> > +       else
> > +               vio_info->read = 1;
> > +
> > +       pr_info(PFX "%s: master_id:0x%x, domain_id:0x%x, rw:%s, vio_addr:0x%x\n",
> > +               __func__, vio_info->master_id, vio_info->domain_id,
> > +               rw ? "Write" : "Read", vio_info->vio_addr);
> > +}
> > +

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