linux-kernel - Re: [PATCH v7 2/2] mtd: rawnand: Add NAND controller support on Intel LGM SoC

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Message-ID: <CAK8P3a25GbMwbtvkxgmuGss6nEfAW4_vVbOXPxOYuDOaU_zcjA@mail.gmail.com>
Date:   Mon, 18 May 2020 13:57:13 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     "Ramuthevar, Vadivel MuruganX" 
        <vadivel.muruganx.ramuthevar@...ux.intel.com>,
        kbuild test robot <lkp@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:MEMORY TECHNOLOGY..." <linux-mtd@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>, kbuild-all@...ts.01.org,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh R <vigneshr@...com>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Anders Roxell <anders.roxell@...aro.org>,
        masonccyang@...c.com.tw
Subject: Re: [PATCH v7 2/2] mtd: rawnand: Add NAND controller support on Intel
 LGM SoC

On Mon, May 18, 2020 at 1:43 PM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
>
> On Mon, May 18, 2020 at 2:39 PM Ramuthevar, Vadivel MuruganX
> <vadivel.muruganx.ramuthevar@...ux.intel.com> wrote:
> > On 15/5/2020 10:30 pm, Arnd Bergmann wrote:
> > > On Fri, May 15, 2020 at 4:25 PM Andy Shevchenko
> > > <andy.shevchenko@...il.com> wrote:
> > >> On Fri, May 15, 2020 at 4:48 PM kbuild test robot <lkp@...el.com> wrote:
>
> > > iowrite_be32() is the correct way to store word into a big-endian mmio register,
> > > if that is the intention here.
> > Thank you for suggestions to use iowrite32be(), it suits exactly.
>
> Can you before doing this comment what is the real intention here?
>
> And note, if you are going to use iowrite*() / ioread*() in one place,
> you will probably need to replace all of the read*() / write*() to
> respective io* API.

The way that ioread/iowrite are defined, they are required to be a superset
of what readl/writel do and can take __iomem pointers from either
ioremap() or ioport_map()/pci_iomap() style mappings, while readl/writel
are only required to work with ioremap().

There is no technical requirement to stick to one set or the other for
ioremap(), but the overhead of ioread/iowrite is also small enough
that it generally does not hurt.

       Arnd