Re: [PATCH/RFC] ARM: boot: Relax kernel image alignment for RZ/A with CS3 SDRAM - Russell King

From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>,
	Arnd Bergmann <arnd@arndb.de>, Nicolas Pitre <nico@fluxnic.net>,
	linux-renesas-soc@vger.kernel.org,
	Chris Brandt <chris.brandt@renesas.com>,
	Eric Miao <eric.miao@nvidia.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH/RFC] ARM: boot: Relax kernel image alignment for RZ/A with CS3 SDRAM
Date: Wed, 13 Nov 2019 10:44:39 +0000	[thread overview]
Message-ID: <20191113104439.GN25745@shell.armlinux.org.uk> (raw)
In-Reply-To: <20191113104037.e45j37xoxeztvut3@pengutronix.de>

On Wed, Nov 13, 2019 at 11:40:37AM +0100, Uwe Kleine-König wrote:
> On Wed, Nov 13, 2019 at 11:27:29AM +0100, Geert Uytterhoeven wrote:
> > The RZA2MEVB sub board has 64 MiB of SDRAM at 0x0C000000 (CS3 space).
> 
> This wording is misleading. You don't adapt the limit because 128 MiB >
> the amount of RAM on that platform but because the alignment of the CS3
> space isn't a multiple of 128 MiB. So I suggest:
> 
> 	On the RZA2MEVB the SDRAM's base is at 0x0C000000 which isn't
> 	aligned to 128 MiB. So to ensure the assumptions of the
> 	decompressor are valid the used alignment must be decreased.
> 
> > Hence the mask for CONFIG_AUTO_ZRELADDR needs to be changed, otherwise
> > the system will crash because it will try to decompress a zImage or
> > uImage to a non-RAM garbage address.
> > 
> > Based on a patch in the BSP by Chris Brandt <chris.brandt@renesas.com>.
> > 
> > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> > ---
> > No idea what to do with the rest of the comment, or if this breaks
> > existing platforms.
> 
> I would assume that it indeed breaks existing platforms. So maybe better
> make this configurable, default to 128 MiB and select it to 64 MiB on
> the affected platform? If the resulting kernel supports also other
> machines a warning (at compile time) might be a good idea.

Are we going back to non-multi-platform kernels? ;)

-- 
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