Date:   Mon, 15 Jun 2020 10:12:47 +0800
From:   Neal Liu <neal.liu@...iatek.com>
To:     Chun-Kuang Hu <chunkuang.hu@...nel.org>
CC:     "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        wsd_upstream <wsd_upstream@...iatek.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 2/2] soc: mediatek: devapc: add devapc-mt6873 driver

Hi Chun-Kuang,


On Fri, 2020-06-12 at 23:27 +0800, Chun-Kuang Hu wrote:
> Hi, Neal:
> 
> Neal Liu <neal.liu@...iatek.com> 於 2020年6月12日 週五 上午11:04寫道：
> >
> > Hi Chun-Kuang,
> >
> > [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, void *dev_id)
> > > > > > +{
> > > > > > +       u32 slave_type_num = mtk_devapc_ctx->soc->slave_type_num;
> > > > > > +       const struct mtk_device_info **device_info;
> > > > > > +       struct mtk_devapc_vio_info *vio_info;
> > > > > > +       int slave_type, vio_idx, index;
> > > > > > +       const char *vio_master;
> > > > > > +       unsigned long flags;
> > > > > > +       bool normal;
> > > > > > +       u8 perm;
> > > > > > +
> > > > > > +       spin_lock_irqsave(&devapc_lock, flags);
> > > > > > +
> > > > > > +       device_info = mtk_devapc_ctx->soc->device_info;
> > > > > > +       vio_info = mtk_devapc_ctx->soc->vio_info;
> > > > > > +       normal = false;
> > > > > > +       vio_idx = -1;
> > > > > > +       index = -1;
> > > > > > +
> > > > > > +       /* There are multiple DEVAPC_PD */
> > > > > > +       for (slave_type = 0; slave_type < slave_type_num; slave_type++) {
> > > > > > +               if (!check_type2_vio_status(slave_type, &vio_idx, &index))
> > > > > > +                       if (!mtk_devapc_dump_vio_dbg(slave_type, &vio_idx,
> > > > > > +                                                    &index))
> > > > > > +                               continue;
> > > > > > +
> > > > > > +               /* Ensure that violation info are written before
> > > > > > +                * further operations
> > > > > > +                */
> > > > > > +               smp_mb();
> > > > > > +               normal = true;
> > > > > > +
> > > > > > +               mask_module_irq(slave_type, vio_idx, true);
> > > > > > +
> > > > > > +               if (clear_vio_status(slave_type, vio_idx))
> > > > > > +                       pr_warn(PFX "%s, %s:0x%x, %s:0x%x\n",
> > > > > > +                               "clear vio status failed",
> > > > > > +                               "slave_type", slave_type,
> > > > > > +                               "vio_index", vio_idx);
> > > > > > +
> > > > > > +               perm = get_permission(slave_type, index, vio_info->domain_id);
> > > > > > +
> > > > > > +               vio_master = mtk_devapc_ctx->soc->master_get
> > > > > > +                       (vio_info->master_id,
> > > > > > +                        vio_info->vio_addr,
> > > > > > +                        slave_type,
> > > > > > +                        vio_info->shift_sta_bit,
> > > > > > +                        vio_info->domain_id);
> > > > >
> > > > > Call mt6873_bus_id_to_master() directly. For first patch, make things
> > > > > as simple as possible.
> > > >
> > > > In devapc_violation_irq() function, we use common flow to handle each
> > > > devapc violation on different platforms. The master_get() has different
> > > > implementation on different platforms, that why it called indirectly.
> > > >
> > > > Once we have new platform, we only have to update devapc-mtxxxx.c
> > > > instead of common handler flow.
> > >
> > > You just upstream one SoC now, so I have no information of 2nd SoC.
> > > Without the 2nd SoC, how do we know what is common and what is SoC special?
> > > So the first patch should not consider the things which does not exist yet.
> > >
> > > Regards,
> > > Chun-Kuang.
> > >
> >
> > It has lots of refactoring work need to do if you really want make it
> > "simple". Could I explain more details and let you judge it is simple
> > enough?
> 
> Making driver "simple" is very important, so it worth to spend effort
> to make things simple. Everybody could modify this driver, so make
> this driver simple and everybody would join this easily.
> 
> > For most MediaTek DEVAPC hw, the violation interrupt handling sequence
> > is shown below.
> >
> > 1. Domain processor receives a interrupt issued by DEVAPC.
> > 2. Software read the violation status and identify it.
> > 3. Software read the debug information which are stored in hw register.
> >         a. debug information includes master ID, domain ID, violation
> > address, ...
> > 4. Transfer debug information to human readable strings.
> > 5. Extra handler to dispatch owner directly.
> 
> I don't know why need extra handler? What does this extra handler could do?
> If indeed need it, separate extra handler part to an independent patch.

Yes, You are right. I'll make this driver more simple and let everybody
can join it easily. This extra handler may not be necessary for whom try
to enable this driver.

> >
> > What we really care is which master violates the rules, and which slave
> > had been accessed unexpectedly.
> >
> > Here are platform specific information:
> > 1. Slaves layout (platform devices)
> > 2. hw register layout which are stored violation information
> > 3. Master ID mapping table
> > 4. Domain ID mapping table
> >
> > Hope these steps could help you understand what is common and what is
> > SoC specific. If you want to see the 2nd SoC's driver, I can also send
> > it for you to take a look.
> 
> Please upstream 2nd SoC's driver, so I could review common part and
> SoC specific part.
> 
> Regards,
> Chun-Kuang.
> 
> >
> > Thanks,
> > Neal
> >
> > > >
> > > > >
> > > > > > +
> > > > > > +               if (!vio_master) {
> > > > > > +                       pr_warn(PFX "master_get failed\n");
> > > > > > +                       vio_master = "UNKNOWN_MASTER";
> > > > > > +               }
> > > > > > +
> > > > > > +               pr_info(PFX "%s - %s:0x%x, %s:0x%x, %s:0x%x, %s:0x%x\n",
> > > > > > +                       "Violation", "slave_type", slave_type,
> > > > > > +                       "sys_index",
> > > > > > +                       device_info[slave_type][index].sys_index,
> > > > > > +                       "ctrl_index",
> > > > > > +                       device_info[slave_type][index].ctrl_index,
> > > > > > +                       "vio_index",
> > > > > > +                       device_info[slave_type][index].vio_index);
> > > > > > +
> > > > > > +               pr_info(PFX "%s %s %s %s\n",
> > > > > > +                       "Violation - master:", vio_master,
> > > > > > +                       "access violation slave:",
> > > > > > +                       device_info[slave_type][index].device);
> > > > > > +
> > > > > > +               devapc_vio_reason(perm);
> > > > > > +
> > > > > > +               devapc_extra_handler(slave_type, vio_master, vio_idx,
> > > > > > +                                    vio_info->vio_addr);
> > > > > > +
> > > > > > +               mask_module_irq(slave_type, vio_idx, false);
> > > > > > +       }
> > > > > > +
> > > > > > +       if (normal) {
> > > > > > +               spin_unlock_irqrestore(&devapc_lock, flags);
> > > > > > +               return IRQ_HANDLED;
> > > > > > +       }
> > > > > > +
> > > > > > +       spin_unlock_irqrestore(&devapc_lock, flags);
> > > > > > +       return IRQ_HANDLED;
> > > > > > +}
> > > > > > +
> > > >
> > > > [snip]
> > > >
> > > >
> >

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