linux-kernel - RE: [PATCH v3 2/2] misc: Add iop driver for Sunplus SP7021

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Message-ID: <5c01390c485a44b6913dcb42e3677ed1@sphcmbx02.sunplus.com.tw>
Date:   Fri, 17 Dec 2021 15:16:53 +0000
From:   Tony Huang 黃懷厚 <tony.huang@...plus.com>
To:     Arnd Bergmann <arnd@...db.de>,
        Tony Huang <tonyhuang.sunplus@...il.com>
CC:     Rob Herring <robh+dt@...nel.org>,
        DTML <devicetree@...r.kernel.org>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        Derek Kiernan <derek.kiernan@...inx.com>,
        Dragan Cvetic <dragan.cvetic@...inx.com>,
        gregkh <gregkh@...uxfoundation.org>,
        Wells Lu 呂芳騰 <wells.lu@...plus.com>
Subject: RE: [PATCH v3 2/2] misc: Add iop driver for Sunplus SP7021

Dear Arnd:

> On Thu, Dec 9, 2021 at 9:58 AM Tony Huang <tonyhuang.sunplus@...il.com>
> wrote:
> >
> > IOP (IO Processor) embedded inside SP7021 which is used as Processor
> > for I/O control, RTC wake-up and cooperation with CPU & PMC in power
> > management purpose.
> > The IOP core is DQ8051, so also named IOP8051, it supports dedicated
> > JTAG debug pins which share with SP7021.
> > In standby mode operation, the power spec reach 400uA.
> >
> > Signed-off-by: Tony Huang <tonyhuang.sunplus@...il.com>
> 
> Thanks for the improvements, this again looks better than the previous version.
> I still have some minor comments, and there are a couple of details I have
> commented on before that would need to be addressed, but let's focus on the
> one main issue for now:
> 
> The driver still doesn't actually /do/ anything: you load the firmware when the
> driver is loaded, and you shut it down when the driver is removed, but
> otherwise there is no way to interact with the iop. You had the miscdevice
> earlier, and you still register that, but there are no file_operations associated
> with it, so it still doesn't have any effect.
> 
> In the original version you had a couple of user-side interfaces, for which Greg
> and I commented that they were not using the correct abstractions, and you
> still list them in the changelog text as "I/O control, RTC wake-up and
> cooperation with CPU & PMC in power management".
> 
> If you want to make any progress with adding the driver, I'd say you should
> implement at least two of those high-level interfaces that interact with the
> respective kernel subsystems in order to show that the abstraction works.
> 

Q:"with respective kernel subsystems in order to show that the abstraction works."
May I ask you about repective kernel subsystem.
If I use the file_operation method
Provide user can read and write IOP(8051)'s register.
Is this a repective kernel subsystem?
if not
There are other driver code can give me reference