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

Neal Liu
2020-07-10T03:34:15Z

Hi Chun-Kuang,

Thanks for your review.

On Thu, 2020-07-09 at 21:01 +0800, Chun-Kuang Hu wrote:
> Hi, Neal:
>
> Neal Liu <neal.liu@mediatek.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@mediatek.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.
>

yes, my mistake. I'll remove it on next patch.

> > +{
> > + 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.

slave_type_num is depends on DT data, it's not always 1.

>
> > + 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?

It has to mask slave's irq before clear violation status.
It's one of hardware design.

>
> > +
> > + 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.

We need to print it as our debug information.
But I did not apply it on this patch, I'll add it on next patch.

>
> > + int ctrl_index;
>
> Ditto.
>
> Regards,
> Chun-Kuang.
>
> > + int vio_index;
> > +};
> > +