linux-kernel - Re: [PATCH v10 10/10] mtd: maps: gpio-addr-flash: Add support for device-tree devices

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Message-ID: <CAPybu_38xH2Cv+eONQmEJ1i6k=oiQM=WrcwOFR29LbtRvWfKXA@mail.gmail.com>
Date:   Fri, 5 Oct 2018 10:10:22 +0200
From:   Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
To:     Boris Brezillon <boris.brezillon@...tlin.com>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Zhouyang Jia <jiazhouyang09@...il.com>,
        linux-mtd@...ts.infradead.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v10 10/10] mtd: maps: gpio-addr-flash: Add support for
 device-tree devices

On Fri, Oct 5, 2018 at 9:08 AM Boris Brezillon
<boris.brezillon@...tlin.com> wrote:
>
> Hi Ricardo,
>
> On Fri, 5 Oct 2018 08:31:35 +0200
> Ricardo Ribalda Delgado <ricardo.ribalda@...il.com> wrote:
>
> > Hi Boris
> >
> >
> > On Fri, Oct 5, 2018 at 12:21 AM Boris Brezillon
> > <boris.brezillon@...tlin.com> wrote:
> > >
> > > Hi Ricardo,
> > >
> > > On Thu,  4 Oct 2018 16:29:42 +0200
> > > Ricardo Ribalda Delgado <ricardo.ribalda@...il.com> wrote:
> > >
> > > > Allow creating gpio-addr-flash via device-tree and not just via platform
> > > > data.
> > > >
> > > > Mimic what physmap_of_versatile and physmap_of_gemini does to reduce
> > > > code duplicity.
> > > >
> > > > Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
> > > > ---
> > > >  drivers/mtd/maps/Kconfig           |  8 +++
> > > >  drivers/mtd/maps/Makefile          |  3 +-
> > > >  drivers/mtd/maps/gpio-addr-flash.c | 95 +++++++++++++++++++-----------
> > > >  drivers/mtd/maps/gpio-addr-flash.h | 34 +++++++++++
> > > >  drivers/mtd/maps/physmap_of_core.c |  5 ++
> > > >  drivers/mtd/maps/physmap_of_gpio.c | 21 +++++++
> > > >  6 files changed, 129 insertions(+), 37 deletions(-)
> > > >  create mode 100644 drivers/mtd/maps/gpio-addr-flash.h
> > > >  create mode 100644 drivers/mtd/maps/physmap_of_gpio.c
> > > >
> > > > diff --git a/drivers/mtd/maps/Kconfig b/drivers/mtd/maps/Kconfig
> > > > index afb36bff13a7..427143d42168 100644
> > > > --- a/drivers/mtd/maps/Kconfig
> > > > +++ b/drivers/mtd/maps/Kconfig
> > > > @@ -94,6 +94,14 @@ config MTD_PHYSMAP_OF_GEMINI
> > > >         platforms, some detection and setting up parallel mode on the
> > > >         external interface.
> > > >
> > > > +config MTD_PHYSMAP_OF_GPIO
> > > > +     bool "GPIO-assisted OF-based physical memory map handling"
> > > > +     depends on MTD_PHYSMAP_OF
> > > > +     depends on MTD_GPIO_ADDR
> > > > +     help
> > > > +       This provides some extra DT physmap parsing for flashes that are
> > > > +       partially physically addressed and assisted by GPIOs.
> > > > +
> > >
> > > Hm, so now we have the physmap_of driver which uses a function exposed
> > > by the gpio-addr-flash module, but this module is also declaring a
> > > platform_driver. It's probably working fine, but it's hard to follow.
> > >
> > > So, I decided to give it a try and started to rework a bit the physmap,
> > > physmap_of and gpio-addr-flash drivers. Here is the result [1] (it's
> > > only been compile tested). With this rework we now have a single
> > > driver which supports DT and !DT init and can also use GPIOs to
> > > extend the physical memory range in case it's not large enough to
> > > address the whole memory dev.
> > >
> > > Let me know what you think of this approach.
> > >
> >
> > The code is definitely easier to follow. But I believe you should
> > rebase your changes on mines (1-9) and instead of 10 apply your
> > patch-set.:
> > - "mtd: maps: Merge gpio-addr-flash.c into physmap-core.c" includes
> > all my changes and some of them are not obvious:( Port to gpiod,
> > gpio_values, win_order, use new apis....)
>
> True.
>
> > - Also there would be 1 (or 2) fixes that should be included in stable
> > that we lose using your approach "mtd: maps: gpio-addr-flash: Fix
> > ioremapped size", "mtd: physmap_of: Release resources on error"
>
> I'm not sure this is really useful to backport them to stable since
> blackfin users never complained about it (plus, blackin arch is now
> gone), but okay.
>
> > - And last, but not least, I want some credit for all this work ;)
> > After 10 iterations I guess that I deserve more than a Documentation
> > change, specially when my code would be on the tree.
>
> Fair enough.
>
> >
> > My other concern is that maybe we are giving too much entity to
> > gpio-addr by including it in the core. But if you are fine with it, I
> > am fine with it.
>
> Well, the gpio-addr stuff is just here to support platforms that do not
> have enough ADDR lines (or iomem address space) to address the whole
> device. I see it as an 'extension' of the physmap logic, which is why I
> think it makes sense to have this logic in the physmap driver instead
> of creating a completely new driver.
>
> >
> > If you want i can do the rebase and start testing on my board. What do
> > you think?
>
> That'd be great!

Can you start by picking 1-8 from my patchset so i do not have to
resend it again and again while we work on your changes?


Thanks!
>
> Thanks,
>
> Boris



-- 
Ricardo Ribalda