From: Arnd Bergmann <arnd@arndb.de>
To: Logan Gunthorpe <logang@deltatee.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
linux-ntb@googlegroups.com, linux-crypto@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jyri Sarha <jsarha@ti.com>, Stephen Bates <sbates@raithlin.com>,
Christoph Hellwig <hch@lst.de>,
Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Subject: Re: [PATCH v2 1/3] io-64-nonatomic: add io{read|write}64[be] macros
Date: Wed, 28 Jun 2017 12:11:37 +0200 [thread overview]
Message-ID: <CAK8P3a2tL5wdCRscpyb6fW+LQVM05urud=YQRS-3+=4w53rmvg@mail.gmail.com> (raw)
In-Reply-To: <20170627230204.16410-2-logang@deltatee.com>
On Wed, Jun 28, 2017 at 1:02 AM, Logan Gunthorpe <logang@deltatee.com> wrote:
> This patch adds io{read|write}64[be] macros to point to the readq/writeq
> in use.
>
> This is because new drivers are encouraged to use ioreadXX, et al instead
> of readX[1], et al -- and mixing ioreadXX with readq is pretty ugly.
>
> [1] ldd3: section 9.4.2
>
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> cc: Christoph Hellwig <hch@lst.de>
> cc: Arnd Bergmann <arnd@arndb.de>
> cc: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
> cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
> include/linux/io-64-nonatomic-hi-lo.h | 16 ++++++++++++++++
> include/linux/io-64-nonatomic-lo-hi.h | 16 ++++++++++++++++
> 2 files changed, 32 insertions(+)
>
> diff --git a/include/linux/io-64-nonatomic-hi-lo.h b/include/linux/io-64-nonatomic-hi-lo.h
> index defcc4644ce3..07a75831244f 100644
> --- a/include/linux/io-64-nonatomic-hi-lo.h
> +++ b/include/linux/io-64-nonatomic-hi-lo.h
> @@ -54,4 +54,20 @@ static inline void hi_lo_writeq_relaxed(__u64 val, volatile void __iomem *addr)
> #define writeq_relaxed hi_lo_writeq_relaxed
> #endif
>
> +#ifndef ioread64
> +#define ioread64 readq
> +#endif
This is wrong since ioread* is not the same read* on x86 and other
architectures that have native PCI PIO accessors, or that require
additional barriers for those.
You have to copy hi_lo_readq() here, and call ioread32 twice instead
of calling readl() twice. Same for iowrite64.
> +#ifndef ioread64be
> +#define ioread64be(p) be64_to_cpu(ioread64(p))
> +#endif
This has another problem: ioread64() is defined to access little-endian
registers, just like readq(). This means that instead of be64_to_cpu()
you need swab64() and always perform the byte swap, otherwise this
would be broken on big-endian architectures.
Arnd
next prev parent reply other threads:[~2017-06-28 10:11 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-27 23:02 [PATCH v2 0/3] make io{read|write}64 more globally usable Logan Gunthorpe
2017-06-27 23:02 ` [PATCH v2 1/3] io-64-nonatomic: add io{read|write}64[be] macros Logan Gunthorpe
2017-06-28 10:11 ` Arnd Bergmann [this message]
2017-06-28 16:02 ` Logan Gunthorpe
2017-06-27 23:02 ` [PATCH v2 2/3] ntb: ntb_hw_intel: use io-64-nonatomic instead of in-driver hacks Logan Gunthorpe
2017-06-27 23:02 ` [PATCH v2 3/3] crypto: caam: cleanup CONFIG_64BIT ifdefs when using io{read|write}64 Logan Gunthorpe
2017-06-28 10:20 ` Arnd Bergmann
2017-06-28 16:51 ` Logan Gunthorpe
2017-06-29 7:52 ` Horia Geantă
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