linux-kernel - Re: [PATCH] ramoops appears geared to not support ARM

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Message-ID: <4EAC0C18.5090602@gmail.com>
Date:	Sat, 29 Oct 2011 16:22:16 +0200
From:	Marco Stornelli <marco.stornelli@...il.com>
To:	Bryan Freed <bfreed@...omium.org>
CC:	linux-kernel@...r.kernel.org, sergiu@...omium.org,
	akpm@...ux-foundation.org, msb@...omium.org, seiji.aguchi@....com
Subject: Re: [PATCH] ramoops appears geared to not support ARM

Il 29/10/2011 01:21, Bryan Freed ha scritto:
> I had some difficulty in getting ramoops to work on our ARM systems.
> The driver maps memory with ioremap() which is supposed to map IO memory,
> not physical RAM.  This happens to work on x86 and apparently some other
> architectures, but it does not work on ARM.
> Specifically, I see this comment in __arm_ioremap_pfn_caller():
> 	Don't allow RAM to be mapped - this causes problems with ARMv6+
>
> So here is a patch that hacks around the issue using page_is_ram() to
> differentiate between the two.
>
> Am I missing something here?
> Is ramoops working on any ARM systems yet, and I am just doing something wrong?
>
> My ARM platform reserves a section of RAM for use by ramoops, but it is still
> mapped along with the rest of main memory.  This is so /dev/mem can find it
> with xlate_dev_mem_ptr().
> On x86, I see our BIOS reserves the memory so that it is not counted as main
> memory, and it is not mapped until ramoops ioremaps it.
>
> Bryan Freed (1):
>    ramoops: Add support for ARM systems.
>
>   drivers/char/ramoops.c |   67 +++++++++++++++++++++++++++++++++++++----------
>   1 files changed, 52 insertions(+), 15 deletions(-)
>

Bryan,

I think the right thing to do here, it's to reserve in right way the 
piece of RAM you use according to your arch (see the Russell response).

Marco
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