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

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Date:   Fri, 9 Oct 2020 14:34:56 +0200
From:   Matthias Brugger <matthias.bgg@...il.com>
To:     Neal Liu <neal.liu@...iatek.com>
Cc:     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 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