From: emilio@elopez•com.ar (Emilio López)
To: linux-arm-kernel@lists•infradead.org
Subject: [RFC 0/4] Create infrastructure for running C code from SRAM.
Date: Wed, 04 Sep 2013 16:52:36 -0300 [thread overview]
Message-ID: <52278F84.2080509@elopez.com.ar> (raw)
In-Reply-To: <1378226665-27090-1-git-send-email-Russ.Dill@ti.com>
Hi,
El 03/09/13 13:44, Russ Dill escribi?:
> This RFC patchset explores an idea for loading C code into SRAM.
> Currently, all the code I'm aware of that needs to run from SRAM is written
> in assembler. The most common reason for code needing to run from SRAM is
> that the memory controller is being disabled/ enabled or is already
> disabled. arch/arm has by far the most examples, but code also exists in
> powerpc and sh.
>
> The code is written in asm for two primary reasons. First so that markers
> can be put in indicating the size of the code they it can be copied. Second
> so that data can be placed along with text and accessed in a position
> independant manner.
>
> SRAM handling code is in the process of being moved from arch directories
> into drivers/misc/sram.c using device tree and genalloc [1] [2]. This RFC
> patchset builds on that, including the limitation that the SRAM address is
> not known at compile time. Because the SRAM address is not known at compile
> time, the code that runs from SRAM must be compiled with -fPIC. Even if
> the code were loaded to a fixed virtual address, portions of the code must
> often be run with the MMU disabled.
>
> The general idea is that for each SRAM user (such as an SoC specific
> suspend/resume mechanism) to create a group of sections. The section group
> is created with a single macro for each user, but end up looking like this:
>
> .sram.am33xx : AT(ADDR(.sram.am33xx) - 0) {
> __sram_am33xx_start = .;
> *(.sram.am33xx.*)
> __sram_am33xx_end = .;
> }
>
> Any data or functions that should be copied to SRAM for this use should be
> maked with an appropriate __section() attribute. A helper is then added for
> translating between the original kernel symbol, and the address of that
> function or variable once it has been copied into SRAM. Once control is
> passed to a function within the SRAM section grouping, it can access any
> variables or functions within that same SRAM section grouping without
> translation.
>
> [1] http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=4984c6
> [2] http://www.spinics.net/lists/linux-omap/msg96504.html
>
> Russ Dill (4):
> Misc: SRAM: Create helpers for loading C code into SRAM
> ARM: SRAM: Add macro for generating SRAM resume trampoline
> Misc: SRAM: Hack for allowing executable code in SRAM.
> ARM: AM33XX: Move suspend/resume assembly to C
>
> arch/arm/include/asm/suspend.h | 14 ++
> arch/arm/kernel/vmlinux.lds.S | 2 +
> arch/arm/mach-omap2/Makefile | 2 +-
> arch/arm/mach-omap2/pm33xx.c | 50 ++---
> arch/arm/mach-omap2/pm33xx.h | 23 +--
> arch/arm/mach-omap2/sleep33xx.S | 394 --------------------------------------
> arch/arm/mach-omap2/sleep33xx.c | 309 ++++++++++++++++++++++++++++++
> arch/arm/mach-omap2/sram.c | 15 --
> drivers/misc/sram.c | 106 +++++++++-
> include/asm-generic/vmlinux.lds.h | 7 +
> include/linux/sram.h | 44 +++++
> 11 files changed, 509 insertions(+), 457 deletions(-)
> delete mode 100644 arch/arm/mach-omap2/sleep33xx.S
> create mode 100644 arch/arm/mach-omap2/sleep33xx.c
> create mode 100644 include/linux/sram.h
>
I'm interested in this, as I'll need something like it for
suspend/resume on sunxi. Unfortunately, I only got the cover letter on
my email, and the web lakml archives don't seem to have the rest either.
After a bit of searching on Google I found a copy on linux-omap[1], but
it'd be great if I didn't have to hunt for the patches :)
I only have one comment, from a quick look at the code
+ memcpy((void *) chunk->addr, data, sz);
+ flush_icache_range(chunk->addr, chunk->addr + sz);
How would that behave on Thumb-2 mode? I believe that's the reason why
fncpy() got introduced[2] some time ago.
Thanks for working on this!
Emilio
[1] http://www.mail-archive.com/linux-omap at vger.kernel.org/msg94995.html
[2] http://www.spinics.net/lists/arm-kernel/msg110706.html
next prev parent reply other threads:[~2013-09-04 19:52 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-03 16:44 [RFC 0/4] Create infrastructure for running C code from SRAM Russ Dill
[not found] ` <1378226665-27090-4-git-send-email-Russ.Dill@ti.com>
2013-09-04 18:06 ` [RFC 3/4] Misc: SRAM: Hack for allowing executable code in SRAM Tony Lindgren
2013-09-06 20:50 ` Russ Dill
2013-09-04 19:52 ` Emilio López [this message]
2013-09-04 21:47 ` [RFC 0/4] Create infrastructure for running C code from SRAM Russ Dill
2013-09-06 11:02 ` Sekhar Nori
2013-09-06 11:14 ` Russell King - ARM Linux
2013-09-06 16:40 ` Dave Martin
2013-09-06 18:50 ` Russ Dill
2013-09-07 8:57 ` Russell King - ARM Linux
2013-09-06 18:40 ` Russ Dill
2013-09-06 11:12 ` Russell King - ARM Linux
2013-09-06 16:19 ` Dave Martin
2013-09-06 19:42 ` Russ Dill
2013-09-06 19:32 ` Russ Dill
2013-09-07 16:21 ` Ard Biesheuvel
2013-09-09 23:10 ` Russ Dill
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=52278F84.2080509@elopez.com.ar \
--to=emilio@elopez$(echo .)com.ar \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
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