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Message-ID: <65d62b60.050a0220.c7b96.614e@mx.google.com>
Date: Wed, 21 Feb 2024 17:57:00 +0100
From: Christian Marangi <ansuelsmth@gmail.com>
To: Russell King <linux@armlinux.org.uk>, Arnd Bergmann <arnd@arndb.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Linus Walleij <linus.walleij@linaro.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Jonathan Corbet <corbet@lwn.net>, Marc Zyngier <maz@kernel.org>,
	"Mike Rapoport (IBM)" <rppt@kernel.org>,
	Eric DeVolder <eric.devolder@oracle.com>,
	Nathan Chancellor <nathan@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	"Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>,
	linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
	Bjorn Andersson <andersson@kernel.org>,
	Konrad Dybcio <konrad.dybcio@somainline.org>,
	John Crispin <john@phrozen.org>
Subject: Re: [PATCH v2 0/2] ARM: decompressor: support AUTO_ZRELADDR and
 appended DTB
References: <20240121203009.9257-1-ansuelsmth@gmail.com>
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In-Reply-To: <20240121203009.9257-1-ansuelsmth@gmail.com>

On Sun, Jan 21, 2024 at 09:29:32PM +0100, Christian Marangi wrote:
> This series try to address a long lasting problem with legacy device
> that require an appended DTB and the use of AUTO_ZRELADDR.
> 
> With these device AUTO_ZRELADDR is not possible if for some reason at
> the start of the RAM it's needed to reserve some space. (example qcom SoC
> that allocate reserved space for SMEM)
> 
> In the current implementation with appended DTB and AUTO_ZRELADDR,
> the memory start is only derived from the PC register and it can't be
> changed by declaring additional info in the DTS.
> 
> In a normal setup, we have an intentional undocumented chosen property
> to handle this and the memory node to declare the start of the memory.
> 
> With this applied and ARM_ATAG_DTB_COMPAT_IGNORE_MEM enabled (more 
> info in the related patch) ipq806x can boot right away with AUTO_ZRELADDR
> enabled and a correct memory node defined in DTS.
> 
> It's needed to ignore MEM ATAGs as most of the time the values from the
> bootloader are hardcoded and OEM didn't care to actually provide them
> resulting in funny situation where a Netgear R7800 with 512Mb of RAM
> have Uboot passing 1.7GB of RAM with ATAGS.
> 
> While MEM ATAG may be broken, other ATAG like serial number or bootargs
> might still be useful for partition declaration (cmdlinepart) or other
> info hence DTB_COMPAT is still needed in these case and can't be
> disabled.
> 
> I'm open to any suggestion on how this can be improved and I would love
> some additional testing on other legacy platform but I assume this will
> permit many legacy device to be correctly supported without having to
> hardcode address.
> 
> Changes v2:
> - Add Review and Ack Tags
> - Use IS_ENABLED instead of global variable
> 
> Christian Marangi (2):
>   ARM: decompressor: support memory start validation for appended DTB
>   ARM: decompressor: add option to ignore MEM ATAGs
> 
>  arch/arm/Kconfig                        | 12 ++++++++++++
>  arch/arm/boot/compressed/atags_to_fdt.c |  4 ++++
>  arch/arm/boot/compressed/head.S         | 22 ++++++++++++++++++++++
>  3 files changed, 38 insertions(+)
> 
>

Any news for this?

-- 
	Ansuel