From: Lukasz Stelmach <l.stelmach@samsung.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "Russell King - ARM Linux admin" <linux@armlinux.org.uk>,
"Dmitry Osipenko" <digetx@gmail.com>,
"Nicolas Pitre" <nico@fluxnic.net>,
"Arnd Bergmann" <arnd@arndb.de>,
"Eric Miao" <eric.miao@nvidia.com>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Masahiro Yamada" <masahiroy@kernel.org>,
"Ard Biesheuvel" <ardb@kernel.org>,
"Marek Szyprowski" <m.szyprowski@samsung.com>,
"Chris Brandt" <chris.brandt@renesas.com>,
"Linux ARM" <linux-arm-kernel@lists.infradead.org>,
Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Bartlomiej Zolnierkiewicz" <b.zolnierkie@samsung.com>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@vger.kernel.org>, "Rob Herring" <robh+dt@kernel.org>,
"Grant Likely" <grant.likely@arm.com>
Subject: Re: [PATCH v6] ARM: boot: Obtain start of physical memory from DTB
Date: Tue, 19 May 2020 13:46:41 +0200 [thread overview]
Message-ID: <dleftjblmk5eqm.fsf%l.stelmach@samsung.com> (raw)
In-Reply-To: <CAMuHMdU5DG06G4H=+PH+OONMT_9oE==KS=wP+bLgY9xVCez6Ww@mail.gmail.com> (Geert Uytterhoeven's message of "Tue, 19 May 2020 13:21:09 +0200")
[-- Attachment #1: Type: text/plain, Size: 3210 bytes --]
It was <2020-05-19 wto 13:21>, when Geert Uytterhoeven wrote:
> Hi Russell,
>
> CC devicetree
>
> On Tue, May 19, 2020 at 11:46 AM Russell King - ARM Linux admin
> <linux@armlinux.org.uk> wrote:
>> On Tue, May 19, 2020 at 11:44:17AM +0200, Geert Uytterhoeven wrote:
>>> On Tue, May 19, 2020 at 10:54 AM Lukasz Stelmach <l.stelmach@samsung.com> wrote:
>>>> It was <2020-04-29 śro 10:21>, when 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>
>>>>> Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
>>>>> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
>>>>> Tested-by: Dmitry Osipenko <digetx@gmail.com>
>>>>> ---
>>>>
>>>> [...]
>>>>
>>>> Apparently reading physical memory layout from DTB breaks crashdump
>>>> kernels. A crashdump kernel is loaded into a region of memory, that
>>>> is reserved in the original (i.e. to be crashed) kernel. The
>>>> reserved region is large enough for the crashdump kernel to run
>>>> completely inside it and don't modify anything outside it, just
>>>> read and dump the remains of the crashed kernel. Using the
>>>> information from DTB makes the decompressor place the kernel
>>>> outside of the dedicated region.
>>>>
>>>> The log below shows that a zImage and DTB are loaded at 0x18eb8000
>>>> and 0x193f6000 (physical). The kernel is expected to run at
>>>> 0x18008000, but it is decompressed to 0x00008000 (see r4 reported
>>>> before jumping from within __enter_kernel). If I were to suggest
>>>> something, there need to be one more bit of information passed in
>>>> the DTB telling the decompressor to use the old masking technique
>>>> to determain kernel address. It would be set in the DTB loaded
>>>> along with the crashdump kernel.
>>>
>>> Shouldn't the DTB passed to the crashkernel describe which region of
>>> memory is to be used instead?
>>
>> Definitely not. The crashkernel needs to know where the RAM in the
>> machine is, so that it can create a coredump of the crashed kernel.
>
> So the DTB should describe both ;-)
So we can do without the mem= cmdline option which is required
now. Sounds reasonable to me.
--
Łukasz Stelmach
Samsung R&D Institute Poland
Samsung Electronics
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 487 bytes --]
next prev parent reply other threads:[~2020-05-19 11:47 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20200429082134eucas1p2415c5269202529e6b019f2d70c1b5572@eucas1p2.samsung.com>
2020-04-29 8:21 ` [PATCH v6] ARM: boot: Obtain start of physical memory from DTB Geert Uytterhoeven
2020-05-19 8:53 ` Lukasz Stelmach
2020-05-19 9:30 ` Russell King - ARM Linux admin
2020-05-19 9:44 ` Geert Uytterhoeven
2020-05-19 9:46 ` Russell King - ARM Linux admin
2020-05-19 11:21 ` Geert Uytterhoeven
2020-05-19 11:28 ` Arnd Bergmann
2020-05-19 12:11 ` Geert Uytterhoeven
2020-05-19 11:43 ` Russell King - ARM Linux admin
[not found] ` <CGME20200519122044eucas1p1220e8827c66dd1ace94b0a86a34f9c37@eucas1p1.samsung.com>
2020-05-19 12:20 ` Lukasz Stelmach
2020-05-19 12:27 ` Russell King - ARM Linux admin
[not found] ` <CGME20200519125008eucas1p2fe9f14c8f785e956a15097d1eca491c7@eucas1p2.samsung.com>
2020-05-19 12:49 ` Lukasz Stelmach
2020-05-19 13:12 ` Russell King - ARM Linux admin
[not found] ` <CGME20200519140211eucas1p24dbc0f54594983731a2dcdd4a943ae27@eucas1p2.samsung.com>
2020-05-19 14:02 ` Lukasz Stelmach
[not found] ` <CGME20200519114657eucas1p156e85218074a7656b93b162e6242bc56@eucas1p1.samsung.com>
2020-05-19 11:46 ` Lukasz Stelmach [this message]
2020-05-19 13:56 ` Ard Biesheuvel
2020-05-19 14:28 ` Russell King - ARM Linux admin
2020-05-19 14:32 ` Ard Biesheuvel
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=dleftjblmk5eqm.fsf%l.stelmach@samsung.com \
--to=l.stelmach@samsung.com \
--cc=ardb@kernel.org \
--cc=arnd@arndb.de \
--cc=b.zolnierkie@samsung.com \
--cc=chris.brandt@renesas.com \
--cc=devicetree@vger.kernel.org \
--cc=digetx@gmail.com \
--cc=eric.miao@nvidia.com \
--cc=geert@linux-m68k.org \
--cc=grant.likely@arm.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-renesas-soc@vger.kernel.org \
--cc=linux@armlinux.org.uk \
--cc=m.szyprowski@samsung.com \
--cc=masahiroy@kernel.org \
--cc=nico@fluxnic.net \
--cc=robh+dt@kernel.org \
--cc=u.kleine-koenig@pengutronix.de \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
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).