Message-ID: <1596425521.22971.13.camel@mtkswgap22>
Date:   Mon, 3 Aug 2020 11:32:01 +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 23:03 +0800, Chun-Kuang Hu wrote:
> Hi, Neal:
> 
> Neal Liu <neal.liu@...iatek.com> 於 2020年7月31日 週五 上午10:44寫道：
> >
> > Hi Chun-Kuang,
> >
> >
> > On Thu, 2020-07-30 at 00:38 +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]
> > >
> > > > +
> > > > +static int get_shift_group(struct mtk_devapc_context *ctx)
> > > > +{
> > > > +       u32 vio_shift_sta;
> > > > +       void __iomem *reg;
> > > > +
> > > > +       reg = ctx->devapc_pd_base + ctx->offset->vio_shift_sta;
> > > > +       vio_shift_sta = readl(reg);
> > > > +
> > > > +       if (vio_shift_sta)
> > > > +               return __ffs(vio_shift_sta);
> > > > +
> > > > +       return -EIO;
> > > > +}
> > >
> > > get_shift_group() is a small function, I would like to merge this
> > > function into sync_vio_dbg() to make code more simple.
> >
> > This function have a specific functionality. And it would make this
> > driver more readability. I would like to keep it as a function. Is that
> > okay for you?
> 
> After merge, the function would be:
> 
> static bool sync_min_shift_group_vio_dbg(struct mtk_devapc_context *ctx)
> {
>  int min_shift_group;
>  int ret;
>  u32 val;
> 
>  /* find the minimum shift group which has violation */
>  val = readl(ctx->devapc_pd_base + ctx->offset->vio_shift_sta);
>  if (!val)
>     return false;
> 
>  min_shift_group = __ffs(val);
> 
>  /* Assign the group to sync */
>  writel(0x1 << min_shift_group, ctx->devapc_pd_base +
> ctx->offset->vio_shift_sel);
> 
>  /* Start syncing */
>  writel(0x1, ctx->devapc_pd_base + ctx->offset->vio_shift_con);
> 
>  ret = readl_poll_timeout(pd_vio_shift_con_reg, val, val == 0x3, 0,
>      PHY_DEVAPC_TIMEOUT);
>  if (ret) {
>   dev_err(ctx->dev, "%s: Shift violation info failed\n", __func__);
>   return false;
>  }
> 
>  /* Stop syncing */
>  writel(0x0, ctx->devapc_pd_base + ctx->offset->vio_shift_con);
> 
>  /* ? */
>  writel(0x1 << min_shift_group, ctx->devapc_pd_base +
> ctx->offset->vio_shift_sta);
> 
>  return true;
> }
> 
> The whole function is to sync min_shift_group violation info, I don't
> know why separate any part to an independent function? Any function
> call would cause penalty on CPU performance, so I does not like to
> break this function. After good comment, I think every body could
> understand the function of each register.
> After the merge, the code would be so simple as:
> 
> while(sync_min_shift_group_vio_dbg(ctx))
>     devapc_extract_vio_dbg(ctx);
> 

Okay, this looks good to me. I'll apply this on next patch.
Thanks !

> >
> > >
> > > > +
> > >
> > > [snip]
> > >
> > > > +
> > > > +#define PHY_DEVAPC_TIMEOUT     0x10000
> > > > +
> > > > +/*
> > > > + * sync_vio_dbg - do "shift" mechansim" to get full violation information.
> > > > + *                shift mechanism is depends on devapc hardware design.
> > > > + *                Mediatek devapc set multiple slaves as a group. When violation
> > > > + *                is triggered, violation info is kept inside devapc hardware.
> > > > + *                Driver should do shift mechansim to "shift" full violation
> > > > + *                info to VIO_DBGs registers.
> > > > + *
> > > > + */
> > > > +static int sync_vio_dbg(struct mtk_devapc_context *ctx, u32 shift_bit)
> > > > +{
> > > > +       void __iomem *pd_vio_shift_sta_reg;
> > > > +       void __iomem *pd_vio_shift_sel_reg;
> > > > +       void __iomem *pd_vio_shift_con_reg;
> > > > +       int ret;
> > > > +       u32 val;
> > > > +
> > > > +       pd_vio_shift_sta_reg = ctx->devapc_pd_base + ctx->offset->vio_shift_sta;
> > > > +       pd_vio_shift_sel_reg = ctx->devapc_pd_base + ctx->offset->vio_shift_sel;
> > > > +       pd_vio_shift_con_reg = ctx->devapc_pd_base + ctx->offset->vio_shift_con;
> > > > +
> > > > +       /* Enable shift mechansim */
> > > > +       writel(0x1 << shift_bit, pd_vio_shift_sel_reg);
> > > > +       writel(0x1, pd_vio_shift_con_reg);
> > > > +
> > > > +       ret = readl_poll_timeout(pd_vio_shift_con_reg, val, val == 0x3, 0,
> > > > +                                PHY_DEVAPC_TIMEOUT);
> > > > +       if (ret)
> > > > +               dev_err(ctx->dev, "%s: Shift violation info failed\n", __func__);
> > > > +
> > > > +       /* Disable shift mechanism */
> > > > +       writel(0x0, pd_vio_shift_con_reg);
> > > > +       writel(0x0, pd_vio_shift_sel_reg);
> > > > +       writel(0x1 << shift_bit, pd_vio_shift_sta_reg);
> > > > +
> > > > +       return ret;
> > > > +}
> > > > +
> > >
> > > [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;
> > >
> > > What is master_id? How could we use it to debug? For example, if we
> > > get a master_id = 1, what should we do for this?
> > >
> > > > +       vio_info->domain_id = (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 = 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 !

> 
> >
> > > > +       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;
> > >
> > > 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);
> > > > +}
> > > > +
> > >
> > > [snip]
> > >
> > > > +
> > > > +/*
> > > > + * devapc_violation_irq - the devapc Interrupt Service Routine (ISR) will dump
> > > > + *                        violation information including which master violates
> > > > + *                        access slave.
> > > > + */
> > > > +static irqreturn_t devapc_violation_irq(int irq_number,
> > > > +                                       struct mtk_devapc_context *ctx)
> > > > +{
> > > > +       u32 vio_idx;
> > > > +
> > > > +       /*
> > > > +        * Mask slave's irq before clearing vio status.
> > > > +        * Must do it to avoid nested interrupt and prevent
> > > > +        * unexpected behavior.
> > > > +        */
> > > > +       for (vio_idx = 0; vio_idx < ctx->vio_idx_num; vio_idx++)
> > > > +               mask_module_irq(ctx, vio_idx, true);
> > >
> > > I would like to rewrite this for-loop as below to prevent too many
> > > function call in irq handler.
> > >
> > > for (i = 0; i < VIO_MOD_TO_REG_IND(ctx->vio_idx_num); i++)
> > >     writel(0xffffffff, ctx->devapc_pd_base + ctx->offset->vio_mask + 4 * i);
> > >
> >
> > This idea is okay for me. Is there any macro to replace 0xffffffff?
> 
> GENMASK(31, 0);
> 
> >
> > > reg  = readl(ctx->devapc_pd_base + ctx->offset->vio_mask + 4 * i);
> > > reg |= 1 << (ctx->vio_idx_num - 32 * i + 1) - 1;
> > > writel(reg, ctx->devapc_pd_base + ctx->offset->vio_mask + 4 * i);
> >
> > Are you trying to clear the bits which over vio_idx_num?
> > If yes, I think the second line should be:
> > reg &= 1 << (ctx->vio_idx_num - 32 * i) - 1;
> >
> > For example, if vio_idx_num is 40:
> > after for loop:
> > vio_mask0 = 0xffffffff;
> > vio_mask1 = 0xffffffff;
> 
> when vio_idx_num is 40, VIO_MOD_TO_REG_IND(ctx->vio_idx_num) is 1, so
> after for-loop:
> vio_mask0 = 0xffffffff;
> 
> And the code after for-loop just to do this:
> vio_mask1 = 0xff;
> 
> >
> > reg = readl(vio_mask1);
> > reg &= (1 << 8) - 1; (which is 0x000000ff)
> > reg will be 0xff
> > writel(reg, vio_mask1);
> >
> > Does it make sense?
> >
> > Actually, it is okay to overwrite the unused register bits.
> > So it's no matter to do this step.
> 
> OK, the code would be
> 
> for (i = 0; i <= VIO_MOD_TO_REG_IND(ctx->vio_idx_num - 1); i++)
>     writel(GENMASK(31, 0), ctx->devapc_pd_base + ctx->offset->vio_mask + 4 * i);
> 

Yes, this is okay for me.
Thanks !

> Regards,
> Chun-Kuang.
> 
> >
> > >
> > > > +
> > > > +       devapc_dump_vio_dbg(ctx);
> > > > +
> > > > +       /*
> > > > +        * Ensure that violation info are written
> > > > +        * before further operations
> > > > +        */
> > > > +       smp_mb();
> > > > +
> > > > +       for (vio_idx = 0; vio_idx < ctx->vio_idx_num; vio_idx++) {
> > > > +               clear_vio_status(ctx, vio_idx);
> > > > +               mask_module_irq(ctx, vio_idx, false);
> > > > +       }
> > >
> > > Ditto for this for-loop.
> >
> > Ditto.
> >
> > >
> > > > +
> > > > +       return IRQ_HANDLED;
> > > > +}
> > > > +
> > >
> > > [snip]
> > >
> > > > +
> > > > +static int mtk_devapc_probe(struct platform_device *pdev)
> > > > +{
> > > > +       struct device_node *node = pdev->dev.of_node;
> > > > +       struct mtk_devapc_context *ctx;
> > > > +       struct clk *devapc_infra_clk;
> > > > +       u32 devapc_irq;
> > > > +       int ret;
> > > > +
> > > > +       if (IS_ERR(node))
> > > > +               return -ENODEV;
> > > > +
> > > > +       ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
> > > > +       if (!ctx)
> > > > +               return -ENOMEM;
> > > > +
> > > > +       ctx = (struct mtk_devapc_context *)of_device_get_match_data(&pdev->dev);
> > > > +       ctx->dev = &pdev->dev;
> > > > +
> > > > +       ctx->vio_info = devm_kzalloc(&pdev->dev,
> > > > +                                    sizeof(struct mtk_devapc_vio_info),
> > > > +                                    GFP_KERNEL);
> > > > +       if (!ctx->vio_info)
> > > > +               return -ENOMEM;
> > > > +
> > > > +       ctx->devapc_pd_base = of_iomap(node, 0);
> > > > +       if (!ctx->devapc_pd_base)
> > > > +               return -EINVAL;
> > > > +
> > > > +       devapc_irq = irq_of_parse_and_map(node, 0);
> > > > +       if (!devapc_irq)
> > > > +               return -EINVAL;
> > > > +
> > > > +       devapc_infra_clk = devm_clk_get(&pdev->dev, "devapc-infra-clock");
> > > > +       if (IS_ERR(devapc_infra_clk))
> > > > +               return -EINVAL;
> > > > +
> > > > +       if (clk_prepare_enable(devapc_infra_clk))
> > > > +               return -EINVAL;
> > > > +
> > > > +       ret = devm_request_irq(&pdev->dev, devapc_irq,
> > > > +                              (irq_handler_t)devapc_violation_irq,
> > > > +                              IRQF_TRIGGER_NONE, "devapc", ctx);
> > > > +       if (ret)
> > >
> > > You should clk_disable_unprepare(devapc_infra_clk);
> >
> > Yes, I miss this part. Thanks for your remind.
> > I'll update it on next patch.
> >
> > >
> > > > +               return ret;
> > > > +
> > > > +       start_devapc(ctx);
> > > > +
> > > > +       return 0;
> > > > +}
> > > > +
> > > > +static int mtk_devapc_remove(struct platform_device *dev)
> > > > +{
> > >
> > > Ditto.
> >
> > Ditto.
> >
> > >
> > > Regards,
> > > Chun-Kuang.
> > >
> > > > +       return 0;
> > > > +}
> > > > +
> > > > +static struct platform_driver mtk_devapc_driver = {
> > > > +       .probe = mtk_devapc_probe,
> > > > +       .remove = mtk_devapc_remove,
> > > > +       .driver = {
> > > > +               .name = KBUILD_MODNAME,
> > > > +               .of_match_table = mtk_devapc_dt_match,
> > > > +       },
> > > > +};
> > > > +
> > > > +module_platform_driver(mtk_devapc_driver);
> > > > +
> >

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