Re: [PATCH v2] ARM: boot: Obtain start of physical memory from DTB

From: Dmitry Osipenko <digetx@gmail.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Russell King <linux@armlinux.org.uk>
Cc: "Geert Uytterhoeven" <geert+renesas@glider.be>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"Nicolas Pitre" <nico@fluxnic.net>,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
	"Chris Brandt" <chris.brandt@renesas.com>,
	"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
	"linux-tegra@vger.kernel.org" <linux-tegra@vger.kernel.org>,
	"Eric Miao" <eric.miao@nvidia.com>,
	"Linux ARM" <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v2] ARM: boot: Obtain start of physical memory from DTB
Date: Thu, 19 Mar 2020 04:11:00 +0300	[thread overview]
Message-ID: <90c006f2-8c13-2976-008f-37139ca49f37@gmail.com> (raw)
In-Reply-To: <CAMuHMdUGu4eStpYp5W0SKJd8yrLLDTgF4__Jq_n+Z7SWtPM+Cg@mail.gmail.com>

25.02.2020 14:40, Geert Uytterhoeven пишет:
> Hi Marek,
> 
> On Tue, Feb 25, 2020 at 12:24 PM Marek Szyprowski
> <m.szyprowski@samsung.com> wrote:
>> On 27.01.2020 15:07, Geert Uytterhoeven wrote:
>>> Currently, the start address of physical memory is obtained by masking
>>> the program counter with a fixed mask of 0xf8000000.  This mask value
>>> was chosen as a balance between the requirements of different platforms.
>>> However, this does require that the start address of physical memory is
>>> a multiple of 128 MiB, precluding booting Linux on platforms where this
>>> requirement is not fulfilled.
>>>
>>> Fix this limitation by obtaining the start address from the DTB instead,
>>> if available (either explicitly passed, or appended to the kernel).
>>> Fall back to the traditional method when needed.
>>>
>>> This allows to boot Linux on r7s9210/rza2mevb using the 64 MiB of SDRAM
>>> on the RZA2MEVB sub board, which is located at 0x0C000000 (CS3 space),
>>> i.e. not at a multiple of 128 MiB.
>>>
>>> Suggested-by: Nicolas Pitre <nico@fluxnic.net>
>>> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
>>> Reviewed-by: Nicolas Pitre <nico@fluxnic.net>
>>> ---
>>> Against arm/for-next.
>>
>> This patch landed recently in linux-next. It breaks legacy booting from
>> the zImage + appended DT + cmdline/memory info provided via ATAGs. I
>> will debug it further once I find some spare time. What I noticed so
>> far, the cmdline/memory info is not read from the ATAGs, only the values
>> provided via appended DT are used.
> 
> Oops, something happening like this was one of my biggest worries when
> posting this patch... Sorry for the breakage.
> 
> IIUIC, the kernel still boots, but just doesn't use the info passed by ATAGs?
> 
> I'll have a closer look later today.
> In the mean time, I've sent some debug code I used when developing
> this patch, which may be useful, hopefully.

Hello,

NVIDIA Tegra is also affected by this patch. A week ago an updated
version of the patch was pushed into linux-next and now machine doesn't
boot at all.

I couldn't find v3 on the ML, so replying to the v2. Please take a look
and fix the problem, or revert/drop the offending patch, thanks in advance.

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