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

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Date:   Fri, 17 Apr 2020 09:02:34 +0200
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     "Ramuthevar, Vadivel MuruganX" 
        <vadivel.muruganx.ramuthevar@...ux.intel.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

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.