linux-kernel - Re: [PATCH v7 2/2] soc: mediatek: add mt6779 devapc driver

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Message-ID: <1602473098.26774.5.camel@mtkswgap22>
Date:   Mon, 12 Oct 2020 11:24:58 +0800
From:   Neal Liu <neal.liu@...iatek.com>
To:     Matthias Brugger <matthias.bgg@...il.com>
CC:     Neal Liu <neal.liu@...iatek.com>, Rob Herring <robh+dt@...nel.org>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        lkml <linux-kernel@...r.kernel.org>, <wsd_upstream@...iatek.com>
Subject: Re: [PATCH v7 2/2] soc: mediatek: add mt6779 devapc driver

On Fri, 2020-10-09 at 14:34 +0200, Matthias Brugger wrote:
> 
> On 08/10/2020 11:39, Neal Liu wrote:
> > On Thu, 2020-10-08 at 10:45 +0200, Matthias Brugger wrote:
> >>
> >> On 08/10/2020 04:35, Neal Liu wrote:
> >>> On Wed, 2020-10-07 at 12:44 +0200, Matthias Brugger wrote:
> >>>>
> >>>> On 27/08/2020 05:06, Neal Liu wrote:
> [...]
> 
> >>>>> +static int mtk_devapc_probe(struct platform_device *pdev)
> >>>>> +{
> >>>>> +	struct device_node *node = pdev->dev.of_node;
> >>>>> +	struct mtk_devapc_context *ctx;
> >>>>> +	u32 devapc_irq;
> >>>>> +	int ret;
> >>>>> +
> >>>>> +	if (IS_ERR(node))
> >>>>> +		return -ENODEV;
> >>>>> +
> >>>>> +	ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
> >>>>> +	if (!ctx)
> >>>>> +		return -ENOMEM;
> >>>>> +
> >>>>> +	ctx->data = of_device_get_match_data(&pdev->dev);
> >>>>> +	ctx->dev = &pdev->dev;
> >>>>> +
> >>>>> +	ctx->infra_base = of_iomap(node, 0);
> >>>>
> >>>> Does this mean the device is part of the infracfg block?
> >>>> I wasn't able to find any information about it.
> >>>
> >>> I'm not sure why you would ask infracfg block. devapc is parts of our
> >>> SoC infra, it's different with infracfg.
> >>>
> >>
> >> I'm asking because I want to understand the HW better. I'm not able to find any
> >> information in the datasheets. I want to avoid a situation as we had with the
> >> MMSYS where a clock driver was submitted first and later on we realized that
> >> MMSYS is much more then that and we had to work hard to get the driver right.
> >>
> >> Now it's happening with SCPSYS, where a driver with the scpsys compatible was
> >> send years ago. But SCPSYS is much more then the driver submitted. In this case
> >> we opted to write a new driver, but moving from one driver to another one is
> >> painfull and full of problems. For that I want to make sure we fully understand
> >> Device APC (by the way, what does APC stands for?). Is it a totally independent
> >> HW block or is it part of a subsystem, like for example SCP?
> >>
> >> Regards,
> >> Matthias
> > 
> > It's a totally independent HW block instead of a subsystem.
> > I think it's more simple than MMSYS or SCPSYS. But if you would like to
> > understand more about this HW, we could find another way/channel to
> > introduce it.
> > 
> 
> If it's a independent HW block, then we are good. No further information needed 
> by me. I'd just advise to rename the infra_base to something like base, as it 
> made me confuse.
> 
> Thanks!
> Matthias

You can imagine that infra_base means infra devapc base address for
MT6779. In 5G platforms, MediaTek infrastructure would separate into
multiple parts, so does devapc HW. And devapc would be like:
infra_base, peri_base, peri2_base, ...

Thanks.