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

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

Hi Chun-Kuang,

On Sat, 2020-08-01 at 08:12 +0800, Chun-Kuang Hu wrote:
> Hi, Neal:
> 
> This patch is for "mediatek,mt6779-devapc", so I think commit title
> should show the SoC ID.

Okay, I'll change title to 'soc:mediatek: add mt6779 devapc driver'.

> 
> Neal Liu <neal.liu@mediatek.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@mediatek.com>
> > ---
> 
> [snip]
> 
> > +
> > +struct mtk_devapc_context {
> > +       struct device *dev;
> > +       u32 vio_idx_num;
> > +       void __iomem *devapc_pd_base;
> > +       struct mtk_devapc_vio_info *vio_info;
> > +       const struct mtk_devapc_pd_offset *offset;
> > +       const struct mtk_devapc_vio_dbgs *vio_dbgs;
> > +};
> 
> I think this structure should separate the constant part. The constant part is:
> 
> struct mtk_devapc_data {
>     const u32 vio_idx_num;
>     const struct mtk_devapc_pd_offset *offset; /* I would like to
> remove struct mtk_devapc_pd_offset and directly put its member into
> this structure */
>     const struct mtk_devapc_vio_dbgs *vio_dbgs; /* This may disappear */
> };
> 
> And the context is:
> 
> struct mtk_devapc_context {
>     struct device *dev;
>     void __iomem *devapc_pd_base;
>     const struct mtk_devapc_data *data;
> };
> 
> So when you define this, you would not waste memory to store non-constant data.
> 
> static const struct mtk_devapc_data devapc_mt6779 = {
>  .vio_idx_num = 510,
>  .offset = &mt6779_pd_offset,
>  .vio_dbgs = &mt6779_vio_dbgs,
> };
> 

Sorry, I still don't understand why this refactoring will not waste
memory to store non-constant data. Could you explain more details?
To my understanding, we still also have to allocate memory to store dev
& devapc_pd_base.

> Regards,
> Chun-Kuang.
> 
> > +
> > +#endif /* __MTK_DEVAPC_H__ */
> > --
> > 1.7.9.5
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