linux-kernel - Re: [PATCH v1 2/2] mtd: rawnand: Add NAND controller support on Intel LGM SoC

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Message-ID: <c26d937a-e9f1-f0f0-5b08-f20a0bd380ab@linux.intel.com>
Date:   Fri, 17 Apr 2020 15:53:59 +0800
From:   "Ramuthevar, Vadivel MuruganX" 
        <vadivel.muruganx.ramuthevar@...ux.intel.com>
To:     Boris Brezillon <boris.brezillon@...labora.com>
Cc:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        anders.roxell@...aro.org, andriy.shevchenko@...el.com,
        arnd@...db.de, brendanhiggins@...gle.com, cheol.yong.kim@...el.com,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mtd@...ts.infradead.org, masonccyang@...c.com.tw,
        miquel.raynal@...tlin.com, piotrs@...ence.com,
        qi-ming.wu@...el.com, richard@....at, robh+dt@...nel.org,
        tglx@...utronix.de, vigneshr@...com
Subject: Re: [PATCH v1 2/2] mtd: rawnand: Add NAND controller support on Intel
 LGM SoC

Hi Boris,

On 17/4/2020 3:02 pm, Boris Brezillon wrote:
> On Fri, 17 Apr 2020 13:21:39 +0800
> "Ramuthevar, Vadivel MuruganX"
> <vadivel.muruganx.ramuthevar@...ux.intel.com> wrote:
>
>> Hi Boris,
>>
>> On 16/4/2020 7:57 pm, Boris Brezillon wrote:
>>> On Thu, 16 Apr 2020 19:38:03 +0800
>>> "Ramuthevar, Vadivel MuruganX"
>>> <vadivel.muruganx.ramuthevar@...ux.intel.com> wrote:
>>>   
>>>> On 16/4/2020 7:17 pm, Boris Brezillon wrote:
>>>>> On Thu, 16 Apr 2020 18:40:53 +0800
>>>>> "Ramuthevar, Vadivel MuruganX"
>>>>> <vadivel.muruganx.ramuthevar@...ux.intel.com> wrote:
>>>>>      
>>>>>>>>> we'll be happy to have one more of the existing driver converted to
>>>>>>>>> ->exec_op() ;-).
>>>>>>>> I have completely adapted to ->exec_op() hook up to replace the legacy
>>>>>>>> call-back.
>>>>>>> I suspect porting what you've done to the xway driver shouldn't be too
>>>>>>> complicated.
>>>>>> Not ported from xway_nand.c driver , we have developed from the scratch
>>>>>> to make it work on
>>>>>> Intel LGM SoC , it's new x86 ATOM based SoC, IP itself completely
>>>>>> different and most of the registers won't match.
>>>>>> if we port then it would be ugly and also what are the problem may occur
>>>>>> we do not know.
>>>>> Sorry but IMO they look similar enough to try to merge them.
>>>> Thanks! Boris, need suggestion from you since you are maintainer and
>>>> also expertise on mtd-subsystem.
>>> I *was* the maintainer :).
>>>   
>>>> There are different features involved and lines of code is more, if we
>>>> add new driver patches over xway-nand driver
>>> How about retro-fitting the xway logic into your driver then? I mean,
>>> adding a 100 lines of code to your driver to get rid of the 500+ lines
>>> we have in xway_nand.c is still a win.
>>>   
>>>> is completely looks ugly and it may disturb the existing functionality
>>>> as well since we don't have platform to validate:'(.
>>> How ugly? Can you show us? Maybe we can come with a solution to make it
>>> less ugly.
>>>
>>> As for the testing part, there are 4 scenarios:
>>>
>>> 1/ Your changes work perfectly fine on older platforms. Yay \o/!
>>> 2/ You break the xway driver and existing users notice it before this
>>>      series gets merged. Now you found someone to validate your changes.
>>> 3/ You break the xway driver and none of the existing users notice it
>>>      before the driver is merged, but they notice it afterwards. Too bad
>>>      this happened after we've merged the driver, but now you've found
>>>      someone to help you fix the problem :P.
>>> 4/ You break things for old platforms but no one ever complains about
>>>      it, either because there's no users left or because they never
>>>      update their kernels. In any case, that's no longer your problem.
>>>      Someone will remove those old platforms one day and get rid of the
>>>      unneeded code in the NAND driver.
>>>
>>> What's more likely to happen is #3 or #4, and I think the NAND
>>> maintainer would be fine with both.
>>>
>>> Note that the NAND subsystem is full of unmaintained legacy drivers, so
>>> every time we see someone who could help us get rid or update one of
>>> them we have to take this opportunity.
>> Agreed!, Thank you very much for the suggestions and clear inputs.
>> To proceed further, can you please share your inputs to dividing the tasks
>> and patches to be sent if possible.
> Let's start with the new version you were about to post. We'll see how
> we can merge both drivers based on that.

Thank you very much for the review comments and inputs , will post the 
patches soon.

Regards
Vadivel