LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Nicolas Pitre <nicolas.pitre@linaro.org>
To: Grant Likely <grant.likely@secretlab.ca>
Cc: linux-arm-kernel@lists.infradead.org,
	Russell King <linux@arm.linux.org.uk>,
	Catalin Marinas <catalin.marinas@arm.com>,
	devicetree-discuss@lists.ozlabs.org,
	lkml <linux-kernel@vger.kernel.org>,
	Olof Johansson <olof@lixom.net>,
	Jeremy Kerr <jeremy.kerr@canonical.com>,
	John Linn <John.Linn@xilinx.com>,
	Lennert Buijtenhek <buytenh@wantstofly.org>
Subject: Re: [PATCH 1/8] arm/dt: Make __vet_atags also accept a dtb image
Date: Tue, 18 Jan 2011 16:26:17 -0500 (EST)	[thread overview]
Message-ID: <alpine.LFD.2.00.1101181621140.8580@xanadu.home> (raw)
In-Reply-To: <20110118202902.13011.68847.stgit@localhost6.localdomain6>

On Tue, 18 Jan 2011, Grant Likely wrote:

> The dtb is passed to the kernel via register r2, which is the same
> method that is used to pass an atags pointer.  This patch modifies
> __vet_atags to not clear r2 when it encounters a dtb image.
> 
> Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
> ---
>  arch/arm/kernel/head-common.S |   19 +++++++++++++------
>  arch/arm/kernel/head.S        |    8 ++++----
>  2 files changed, 17 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S
> index 8f57515..d9a9105 100644
> --- a/arch/arm/kernel/head-common.S
> +++ b/arch/arm/kernel/head-common.S
> @@ -14,6 +14,7 @@
>  #define ATAG_CORE 0x54410001
>  #define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2)
>  #define ATAG_CORE_SIZE_EMPTY ((2*4) >> 2)
> +#define OF_DT_MAGIC 0xedfe0dd0 /* 0xd00dfeed in big-endian */

ARM can be big endian too.  Would be nice to make this endian 
independent, or at least list this limitation in the commit log.

>  /*
>   * Exception handling.  Something went wrong and we can't proceed.  We
> @@ -105,22 +106,28 @@ __lookup_machine_type_data:
>  
>  /* Determine validity of the r2 atags pointer.  The heuristic requires
>   * that the pointer be aligned, in the first 16k of physical RAM and
> - * that the ATAG_CORE marker is first and present.  Future revisions
> + * that the ATAG_CORE marker is first and present.  If CONFIG_OF_FLATTREE
> + * is selected, then it will also accept a dtb pointer.  Future revisions
>   * of this function may be more lenient with the physical address and
>   * may also be able to move the ATAGS block if necessary.
>   *
>   * r8  = machinfo
>   *
>   * Returns:
> - *  r2 either valid atags pointer, or zero
> + *  r2 either valid atags pointer, valid dtb pointer, or zero
>   *  r5, r6 corrupted
>   */
>  __vet_atags:
>  	tst	r2, #0x3			@ aligned?
>  	bne	1f
>  
> -	ldr	r5, [r2, #0]			@ is first tag ATAG_CORE?
> -	cmp	r5, #ATAG_CORE_SIZE
> +#ifdef CONFIG_OF_FLATTREE
> +	ldr	r5, [r2, #0]			@ is it a DTB?
> +	ldr	r6, =OF_DT_MAGIC
> +	cmp	r5, r6
> +	beq	2f
> +#endif
> +	cmp	r5, #ATAG_CORE_SIZE		@ is first tag ATAG_CORE?

The "ldr r5 ..." is now done only within #ifdef CONFIG_OF_FLATTREE.  So 
if CONFIG_OF_FLATTREE is undefined then r5 will contain garbage.


Nicolas

  reply	other threads:[~2011-01-18 21:26 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-18 20:28 [PATCH 0/8] Basic ARM device tree support Grant Likely
2011-01-18 20:29 ` [PATCH 1/8] arm/dt: Make __vet_atags also accept a dtb image Grant Likely
2011-01-18 21:26   ` Nicolas Pitre [this message]
2011-01-18 21:42     ` Grant Likely
2011-01-18 20:29 ` [PATCH 2/8] arm/dt: allow bootmem reservation for device tree blob and initrd Grant Likely
2011-01-18 20:29 ` [PATCH 3/8] arm/dt: Allow CONFIG_OF on ARM Grant Likely
2011-01-18 20:29 ` [PATCH 4/8] arm/dt: consolidate atags setup into setup_machine_atags Grant Likely
2011-01-18 20:29 ` [PATCH 5/8] arm/dt: probe for platforms via the device tree Grant Likely
2011-01-18 20:29 ` [PATCH 6/8] arm/dt: Basic versatile devicetree support Grant Likely
2011-01-18 20:29 ` [PATCH 7/8] arm/tegra: Fix tegra irq_data conversion Grant Likely
2011-01-18 20:29 ` [PATCH 8/8] arm/dt: Basic tegra devicetree support Grant Likely
2011-01-18 21:47   ` Nicolas Pitre
2011-01-18 21:55     ` Grant Likely
2011-01-19 12:14   ` Sergei Shtylyov
2011-01-26 20:04 ` [PATCH 0/8] Basic ARM device tree support John Linn
2011-01-26 22:32   ` Rob Herring
2011-01-28  6:37     ` Jason Liu
2011-01-31 18:05   ` Grant Likely
2011-01-31 18:06     ` John Linn

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.LFD.2.00.1101181621140.8580@xanadu.home \
    --to=nicolas.pitre@linaro.org \
    --cc=John.Linn@xilinx.com \
    --cc=buytenh@wantstofly.org \
    --cc=catalin.marinas@arm.com \
    --cc=devicetree-discuss@lists.ozlabs.org \
    --cc=grant.likely@secretlab.ca \
    --cc=jeremy.kerr@canonical.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux@arm.linux.org.uk \
    --cc=olof@lixom.net \
    --subject='Re: [PATCH 1/8] arm/dt: Make __vet_atags also accept a dtb image' \
    /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

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).