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

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Date:   Mon, 15 Jun 2020 22:14:09 +0800
From:   Chun-Kuang Hu <chunkuang.hu@...nel.org>
To:     Neal Liu <neal.liu@...iatek.com>
Cc:     Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        devicetree@...r.kernel.org,
        wsd_upstream <wsd_upstream@...iatek.com>,
        linux-kernel <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 2/2] soc: mediatek: devapc: add devapc-mt6873 driver

Hi, Neal:

Neal Liu <neal.liu@...iatek.com> 於 2020年6月15日 週一 上午10:43寫道：
>
> Hi Chun-Kuang,
>
>
> On Sun, 2020-06-14 at 11:26 +0800, Chun-Kuang Hu wrote:
> > Hi, Neal:
> >
> > Neal Liu <neal.liu@...iatek.com> 於 2020年6月9日 週二 下午6:25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@...iatek.com>
> > > ---
> >
> > [snip]
> >
> > > +
> > > +       /* 50 */
> > > +       {-1, -1, 50, "OOB_way_en", true},
> > > +       {-1, -1, 51, "OOB_way_en", true},
> > > +       {-1, -1, 52, "OOB_way_en", true},
> > > +       {-1, -1, 53, "OOB_way_en", true},
> > > +       {-1, -1, 54, "OOB_way_en", true},
> > > +       {-1, -1, 55, "OOB_way_en", true},
> > > +       {-1, -1, 56, "Decode_error", true},
> > > +       {-1, -1, 57, "Decode_error", true},
> > > +       {-1, -1, 58, "DISP_PWM", false},
> > > +       {-1, -1, 59, "IMP_IIC_WRAP", false},
> > > +
> > > +       /* 60 */
> > > +       {-1, -1, 60, "DEVICE_APC_PERI_PAR__AO", false},
> > > +       {-1, -1, 61, "DEVICE_APC_PERI_PAR_PDN", false},
> >
> > You does not process the item whose enable_vio_irq is false, so I
> > think you should remove these items and remove enable_vio_irq because
> > the rest item's enable_vio_irq would always be true.
>
> In some users, they can decide which slaves they want to enable or
> disable violation irq in different product. We remain this property for
> compatibility.

I think in upstream version, you could still remove enable_vio_irq and
process all items. For downstream case, users could remove items they
does not interest in.

>
> >
> > > +};
> > > +
> > > +static struct mtk_device_num mtk6873_devices_num[] = {
> > > +       {SLAVE_TYPE_INFRA, VIO_SLAVE_NUM_INFRA},
> > > +       {SLAVE_TYPE_PERI, VIO_SLAVE_NUM_PERI},
> > > +       {SLAVE_TYPE_PERI2, VIO_SLAVE_NUM_PERI2},
> > > +       {SLAVE_TYPE_PERI_PAR, VIO_SLAVE_NUM_PERI_PAR},
> > > +};
> > > +
> > > +static struct PERIAXI_ID_INFO peri_mi_id_to_master[] = {
> > > +       {"THERM2",       { 0, 0, 0 } },
> > > +       {"SPM",          { 0, 1, 0 } },
> > > +       {"CCU",          { 0, 0, 1 } },
> > > +       {"THERM",        { 0, 1, 1 } },
> > > +       {"SPM_DRAMC",    { 1, 1, 0 } },
> >
> > The bits { 1, 1, 0 } equal to a number 0x3, I thiink you should use a
> > number instead of bits and everything would be more easy.
>
> We would like to keep it because the bit value contains more than 0/1,
> it might be '2' in some cases. '2' means it can be 0 or 1. This totally
> by hardware design & implementation.

Upstream the patch that has dont-care-bits, otherwise, use a number for this.
Even there is dont-care-bits, I have a better way to process it. Here
is an example that has dont-care-bits:

+ {"Tinysys",         { 0, 1, 0, 0, 2, 2, 2, 2, 2, 2, 0, 0, 0, 0 } },

I could use a { value, mask } pair for this case,

value = 0x0002; /* value for care bits */
mask = 0x3c02; /* mask for care bits */

So the compare statement would be

if ((bus_id & mask) == value)

So you could get rid of the second for-loop and reduce the processing
time in irq handler.

Regards,
Chun-Kuang.