From: Paul Walmsley <paul.walmsley@sifive.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Arnd Bergmann <arnd@arndb.de>, Guo Ren <guoren@kernel.org>,
Michal Simek <monstr@monstr.eu>,
Greentime Hu <green.hu@gmail.com>,
Vincent Chen <deanbo422@gmail.com>, Guan Xuetao <gxt@pku.edu.cn>,
x86@kernel.org, linux-arch@vger.kernel.org,
linux-s390@vger.kernel.org, linux-ia64@vger.kernel.org,
linux-parisc@vger.kernel.org, linux-sh@vger.kernel.org,
linux-hexagon@vger.kernel.org, linux-xtensa@linux-xtensa.org,
linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-m68k@lists.linux-m68k.org, openrisc@lists.librecores.org,
linux-mtd@lists.infradead.org, linux-alpha@vger.kernel.org,
sparclinux@vger.kernel.org, nios2-dev@lists.rocketboards.org,
linux-riscv@lists.infradead.org,
linux-snps-arc@lists.infradead.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 15/26] asm-generic: ioremap_uc should behave the same with and without MMU
Date: Sat, 17 Aug 2019 14:07:29 -0700 (PDT) [thread overview]
Message-ID: <alpine.DEB.2.21.9999.1908171403330.4130@viisi.sifive.com> (raw)
In-Reply-To: <20190817073253.27819-16-hch@lst.de>
On Sat, 17 Aug 2019, Christoph Hellwig wrote:
> Whatever reason there is for the existence of ioremap_uc, and the fact
> that it returns NULL by default on architectures with an MMU applies
> equally to nommu architectures, so don't provide different defaults.
>
> In practice the difference is meaningless as the only portable driver
> that uses ioremap_uc is atyfb which probably doesn't show up on nommu
> devices.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
[ ... ]
> diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
> index d02806513670..a98ed6325727 100644
> --- a/include/asm-generic/io.h
> +++ b/include/asm-generic/io.h
[ ... ]
> @@ -1004,6 +985,21 @@ static inline void __iomem *ioremap_wt(phys_addr_t offset, size_t size)
> }
> #endif
>
> +/*
> + * ioremap_uc is special in that we do require an explicit architecture
> + * implementation. In general you do now want to use this function in a
^^^ not
> + * driver and use plain ioremap, which is uncached by default. Similarly
^ instead
> + * architectures should not implement it unless they have a very good
> + * reason.
> + */
Looks like this mess is only needed on x86 with certain graphics drivers
and conflicts between MTRR and page table-based MMU attributes.
Reviewed-by: Paul Walmsley <paul.walmsley@sifive.com>
Tested-by: Paul Walmsley <paul.walmsley@sifive.com> # rv32, rv64 boot
- Paul
next prev parent reply other threads:[~2019-08-17 21:07 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-17 7:32 generic ioremap (and lots of cleanups) Christoph Hellwig
2019-08-17 7:32 ` [PATCH 01/26] mtd/maps/pxa2xx: use ioremap_cache insted of ioremap_cached Christoph Hellwig
2019-08-17 7:32 ` [PATCH 02/26] arm, unicore32: remove ioremap_cached Christoph Hellwig
2019-08-17 7:32 ` [PATCH 03/26] m68k, microblaze: remove ioremap_fullcache Christoph Hellwig
2019-08-19 8:50 ` Geert Uytterhoeven
2019-09-02 14:16 ` Michal Simek
2019-08-17 7:32 ` [PATCH 04/26] mips: remove ioremap_cachable Christoph Hellwig
2019-08-19 20:57 ` Paul Burton
2019-08-30 16:06 ` Christoph Hellwig
2019-09-03 8:57 ` Paul Burton
2019-08-17 7:32 ` [PATCH 05/26] openrisc: map as uncached in ioremap Christoph Hellwig
2019-08-23 13:55 ` Stafford Horne
2019-08-30 16:07 ` Christoph Hellwig
2019-08-30 21:45 ` Stafford Horne
2019-08-17 7:32 ` [PATCH 06/26] ia64: rename ioremap_nocache to ioremap_uc Christoph Hellwig
2019-08-17 16:00 ` Sergei Shtylyov
2019-08-17 7:32 ` [PATCH 07/26] hexagon: clean up ioremap Christoph Hellwig
2019-08-17 7:32 ` [PATCH 08/26] m68k: simplify ioremap_nocache Christoph Hellwig
2019-08-19 8:56 ` Geert Uytterhoeven
2019-08-19 9:18 ` Christoph Hellwig
2019-08-30 16:06 ` Christoph Hellwig
2019-09-02 7:53 ` Geert Uytterhoeven
2019-08-17 7:32 ` [PATCH 09/26] alpha: remove the unused __ioremap wrapper Christoph Hellwig
2019-08-17 7:32 ` [PATCH 10/26] nios2: remove __ioremap Christoph Hellwig
2019-08-17 7:32 ` [PATCH 11/26] parisc: " Christoph Hellwig
2019-08-17 7:32 ` [PATCH 12/26] x86: clean up ioremap Christoph Hellwig
2019-08-17 10:34 ` Ingo Molnar
2019-08-30 16:04 ` Christoph Hellwig
2019-08-17 7:32 ` [PATCH 13/26] xtensa: " Christoph Hellwig
2019-08-17 7:32 ` [PATCH 14/26] asm-generic: don't provide __ioremap Christoph Hellwig
2019-08-17 20:58 ` Paul Walmsley
2019-08-17 21:27 ` Paul Walmsley
2019-08-17 7:32 ` [PATCH 15/26] asm-generic: ioremap_uc should behave the same with and without MMU Christoph Hellwig
2019-08-17 21:07 ` Paul Walmsley [this message]
2019-08-17 7:32 ` [PATCH 16/26] asm-generic: don't provide ioremap for CONFIG_MMU Christoph Hellwig
2019-08-17 21:15 ` Paul Walmsley
2019-08-17 7:32 ` [PATCH 17/26] arch: rely on asm-generic/io.h for default ioremap_* definitions Christoph Hellwig
2019-08-17 21:13 ` Paul Walmsley
2019-08-17 7:32 ` [PATCH 18/26] m68k: rename __iounmap and mark it static Christoph Hellwig
2019-08-19 9:00 ` Geert Uytterhoeven
2019-08-17 7:32 ` [PATCH 19/26] arm64: remove __iounmap Christoph Hellwig
2019-08-19 7:36 ` Will Deacon
2019-08-30 16:05 ` Christoph Hellwig
2019-08-31 16:29 ` Will Deacon
2019-08-17 7:32 ` [PATCH 20/26] hexagon: " Christoph Hellwig
2019-08-17 7:32 ` [PATCH 21/26] nios2: " Christoph Hellwig
2019-08-17 7:32 ` [PATCH 22/26] sh: " Christoph Hellwig
2019-08-17 7:32 ` [PATCH 23/26] lib: provide a simple generic ioremap implementation Christoph Hellwig
2019-08-17 7:32 ` [PATCH 24/26] riscv: use the generic ioremap code Christoph Hellwig
2019-08-17 21:22 ` Paul Walmsley
2019-09-01 8:02 ` Christoph Hellwig
2019-08-17 7:32 ` [PATCH 25/26] csky: use generic ioremap Christoph Hellwig
2019-08-17 7:32 ` [PATCH 26/26] nds32: " Christoph Hellwig
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=alpine.DEB.2.21.9999.1908171403330.4130@viisi.sifive.com \
--to=paul.walmsley@sifive.com \
--cc=arnd@arndb.de \
--cc=deanbo422@gmail.com \
--cc=green.hu@gmail.com \
--cc=guoren@kernel.org \
--cc=gxt@pku.edu.cn \
--cc=hch@lst.de \
--cc=linux-alpha@vger.kernel.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-hexagon@vger.kernel.org \
--cc=linux-ia64@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-m68k@lists.linux-m68k.org \
--cc=linux-mips@vger.kernel.org \
--cc=linux-mtd@lists.infradead.org \
--cc=linux-parisc@vger.kernel.org \
--cc=linux-riscv@lists.infradead.org \
--cc=linux-s390@vger.kernel.org \
--cc=linux-sh@vger.kernel.org \
--cc=linux-snps-arc@lists.infradead.org \
--cc=linux-xtensa@linux-xtensa.org \
--cc=monstr@monstr.eu \
--cc=nios2-dev@lists.rocketboards.org \
--cc=openrisc@lists.librecores.org \
--cc=sparclinux@vger.kernel.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).