linux-kernel - Re: [PATCH v2 2/2] soc: mediatek: add mtk-devapc driver

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Message-ID: <CAAOTY_-7PwoPG_0ce2p4BCNQ3rundg40Bsni14XSmVETExkKkw@mail.gmail.com>
Date:   Thu, 9 Jul 2020 21:01:44 +0800
From:   Chun-Kuang Hu <chunkuang.hu@...nel.org>
To:     Neal Liu <neal.liu@...iatek.com>
Cc:     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 v2 2/2] soc: mediatek: add mtk-devapc driver

Hi, Neal:

Neal Liu <neal.liu@...iatek.com> 於 2020年7月9日 週四 下午5:13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 u32 get_shift_group(struct mtk_devapc_context *devapc_ctx,
> +                          int slave_type, int vio_idx)

vio_idx  is useless, so remove it.

> +{
> +       u32 vio_shift_sta;
> +       void __iomem *reg;
> +       int bit;
> +
> +       reg = mtk_devapc_pd_get(devapc_ctx, slave_type, VIO_SHIFT_STA, 0);
> +       vio_shift_sta = readl(reg);
> +
> +       for (bit = 0; bit < 32; bit++) {
> +               if ((vio_shift_sta >> bit) & 0x1)
> +                       break;
> +       }
> +
> +       return bit;
> +}
> +

[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 *devapc_ctx)
> +{
> +       const struct mtk_device_info **device_info;
> +       int slave_type_num;
> +       int vio_idx = -1;
> +       int slave_type;
> +
> +       slave_type_num = devapc_ctx->slave_type_num;
> +       device_info = devapc_ctx->device_info;
> +
> +       for (slave_type = 0; slave_type < slave_type_num; slave_type++) {

If slave_type_num is 1, I think the code should be simpler.

> +               if (!mtk_devapc_dump_vio_dbg(devapc_ctx, slave_type, &vio_idx))
> +                       continue;
> +
> +               /* Ensure that violation info are written before
> +                * further operations
> +                */
> +               smp_mb();
> +
> +               mask_module_irq(devapc_ctx, slave_type, vio_idx, true);

Why do you mask irq?

> +
> +               clear_vio_status(devapc_ctx, slave_type, vio_idx);
> +
> +               mask_module_irq(devapc_ctx, slave_type, vio_idx, false);
> +       }
> +
> +       return IRQ_HANDLED;
> +}
> +
> +/*
> + * start_devapc - initialize devapc status and start receiving interrupt
> + *               while devapc violation is triggered.
> + */

[snip]

> +
> +struct mtk_device_info {
> +       int sys_index;

Useless, so remove it.

> +       int ctrl_index;

Ditto.

Regards,
Chun-Kuang.

> +       int vio_index;
> +};
> +