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Date: Wed, 1 May 2024 13:20:01 +0200
From: Alexandre Belloni <alexandre.belloni@bootlin.com>
To: Jingbao Qiu <qiujingbao.dlmu@gmail.com>
Cc: Inochi Amaoto <inochiama@outlook.com>, robh+dt@kernel.org,
	krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org,
	paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu,
	linux-rtc@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, dlan@gentoo.org
Subject: Re: [PATCH v8 2/2] rtc: sophgo: add rtc support for Sophgo CV1800 SoC
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On 01/05/2024 17:14:43+0800, Jingbao Qiu wrote:
> On Wed, May 1, 2024 at 3:43 PM Inochi Amaoto <inochiama@outlook.com> wrote:
> >
> > On Wed, May 01, 2024 at 01:03:58PM GMT, Jingbao Qiu wrote:
> > > Hi, Inochi
> > >
> > > On Wed, May 1, 2024 at 10:19 AM Inochi Amaoto <inochiama@outlook.com> wrote:
> 
> > > > Another thing is that I do not think is a good way to let the
> > > > rtc driver access RTC_CTRL area directly. You have already
> > > > know there is a 8051 device in the 0x05025000. It is necessary
> > > > to make some room for this device. Maybe you want to implement
> > > > them all in the rtc driver? If so, I do think it is a bad idea.
> > >
> > >
> > > Do you mean that RTC drivers should not directly access the 0x05025000 address?
> > > Because there is an 8051 subsystem on this address.
> >
> > Yes. At least we need some mechanism to share these address between
> > this devices.
> >
> > > Firstly, I do not intend to implement 8051 in the RTC driver,
> > > but the 8051 subsystem is located within a module independently
> > > powered by the RTC.
> > > So if we want to implement the 8051 subsystem in the future, it can be
> > > used as a node in RTC? I'm not sure.
> >
> > Yes, this is what I care about.
> >
> > > Then, Alexandre told me that there are operations related to PM in
> > > RTC, such as the following files.
> > > This matches the description of address 0x05025000.
> > >
> > > drivers/rtc/rtc jz4740. c
> > >
> >
> > I do not think this is something related to the PM. 8051 is more
> > like remoteproc. So it is necessary to arrange them carefully.
> >
> 
> You are right.
> I learned from official documents that 8051 works in the RTC domain.
> Linux does not provide relevant interfaces to operate 8051,
> Just providing a mailbox for communication between them, or through
> interruptions.
> I don't understand how 8051 works, so I shouldn't write to the
> corresponding registers in RTC.
> 
> https://milkv.io/docs/duo/getting-started/8051core

Then you will have to have a driver for the 8051 firmware before being
able to access registers that are outside of the RTC range. However, I
se the firmware is using RTC_INFOx without any form of locking but I
guess this just means Linux will have to ensure it never writes to
those.

> 
> 
> > > > > 2.25.1
> > > > >

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com