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From: Arnd Bergmann <arnd@kernel.org>
To: Alistair Francis <alistair23@gmail.com>
Cc: Shawn Guo <shawnguo@kernel.org>,
	Alistair Francis <alistair@alistair23.me>,
	Arnd Bergmann <arnd@arndb.de>, Olof Johansson <olof@lixom.net>,
	Rob Herring <robh+dt@kernel.org>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Sascha Hauer <kernel@pengutronix.de>,
	Fabio Estevam <festevam@gmail.com>,
	dl-linux-imx <linux-imx@nxp.com>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	devicetree <devicetree@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 3/3] arch/arm/configs: Enable VMSPLIT_2G in imx_v6_v7_defconfig
Date: Wed, 3 Feb 2021 08:50:02 +0100	[thread overview]
Message-ID: <CAK8P3a1ZLuDTKY6YbPrcM338K4vmAgESeBiNwWN7VaWj2PtKFg@mail.gmail.com> (raw)
In-Reply-To: <CAKmqyKOoTG+BGhRFtppQxnaV61GFxXXhmZJcxqGQVbnuV1PfqA@mail.gmail.com>

On Wed, Feb 3, 2021 at 3:37 AM Alistair Francis <alistair23@gmail.com> wrote:
>
> On Thu, Jan 28, 2021 at 11:13 PM Shawn Guo <shawnguo@kernel.org> wrote:
> >
> > On Sun, Jan 17, 2021 at 10:03:01AM -0800, Alistair Francis wrote:
> > > The reMarkable2 requires VMSPLIT_2G, so lets set this in the
> > > imx_v6_v7_defconfig.
> >
> > Hmm, why is VMSPLIT_2G required by reMarkable2?
>
> I'm not too sure. It's difficult to debug problems as I only have a
> UART but without this I don't see any kernel prints so it seems like
> the kernel doesn't get very far. I haven't had any luck with earlycon
> on the device so I don't know how I can get more information.

In the dts file, I can see that the machine has 1GB of RAM at
contiguous addresses. My first guess would be a problem with
highmem, as this configuration means that with VMSPLIT_3G
there are 768MB of lowmem and 256MB of highmem.

Can you try these two things to narrow the problem down
further?

a) disable CONFIG_HIGHMEM when using VMSPLIT_3G
b) use VMSPLIT_3G_OPT

If both of them solve the problem, then highmem is likely
the root cause. One possible issue might be that the boot
loader loads the initramfs or the dtb into a location outside
of the first 768 MB of lowmem where it is unreachable
in the VMSPLIT_3G configuration.

        Arnd

WARNING: multiple messages have this Message-ID (diff)
From: Arnd Bergmann <arnd@kernel.org>
To: Alistair Francis <alistair23@gmail.com>
Cc: devicetree <devicetree@vger.kernel.org>,
	Arnd Bergmann <arnd@arndb.de>, Fabio Estevam <festevam@gmail.com>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Alistair Francis <alistair@alistair23.me>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	dl-linux-imx <linux-imx@nxp.com>,
	Sascha Hauer <kernel@pengutronix.de>,
	Olof Johansson <olof@lixom.net>, Shawn Guo <shawnguo@kernel.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v2 3/3] arch/arm/configs: Enable VMSPLIT_2G in imx_v6_v7_defconfig
Date: Wed, 3 Feb 2021 08:50:02 +0100	[thread overview]
Message-ID: <CAK8P3a1ZLuDTKY6YbPrcM338K4vmAgESeBiNwWN7VaWj2PtKFg@mail.gmail.com> (raw)
In-Reply-To: <CAKmqyKOoTG+BGhRFtppQxnaV61GFxXXhmZJcxqGQVbnuV1PfqA@mail.gmail.com>

On Wed, Feb 3, 2021 at 3:37 AM Alistair Francis <alistair23@gmail.com> wrote:
>
> On Thu, Jan 28, 2021 at 11:13 PM Shawn Guo <shawnguo@kernel.org> wrote:
> >
> > On Sun, Jan 17, 2021 at 10:03:01AM -0800, Alistair Francis wrote:
> > > The reMarkable2 requires VMSPLIT_2G, so lets set this in the
> > > imx_v6_v7_defconfig.
> >
> > Hmm, why is VMSPLIT_2G required by reMarkable2?
>
> I'm not too sure. It's difficult to debug problems as I only have a
> UART but without this I don't see any kernel prints so it seems like
> the kernel doesn't get very far. I haven't had any luck with earlycon
> on the device so I don't know how I can get more information.

In the dts file, I can see that the machine has 1GB of RAM at
contiguous addresses. My first guess would be a problem with
highmem, as this configuration means that with VMSPLIT_3G
there are 768MB of lowmem and 256MB of highmem.

Can you try these two things to narrow the problem down
further?

a) disable CONFIG_HIGHMEM when using VMSPLIT_3G
b) use VMSPLIT_3G_OPT

If both of them solve the problem, then highmem is likely
the root cause. One possible issue might be that the boot
loader loads the initramfs or the dtb into a location outside
of the first 768 MB of lowmem where it is unreachable
in the VMSPLIT_3G configuration.

        Arnd

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2021-02-03  7:51 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-17 18:02 [PATCH v2 1/3] imx7d-remarkable2.dts: Initial device tree for reMarkable2 Alistair Francis
2021-01-17 18:02 ` Alistair Francis
2021-01-17 18:03 ` [PATCH v2 2/3] arch/arm/configs: Regenerate imx_v6_v7_defconfig Alistair Francis
2021-01-17 18:03   ` Alistair Francis
2021-01-17 18:03 ` [PATCH v2 3/3] arch/arm/configs: Enable VMSPLIT_2G in imx_v6_v7_defconfig Alistair Francis
2021-01-17 18:03   ` Alistair Francis
2021-01-29  7:13   ` Shawn Guo
2021-01-29  7:13     ` Shawn Guo
2021-02-03  2:37     ` Alistair Francis
2021-02-03  2:37       ` Alistair Francis
2021-02-03  7:50       ` Arnd Bergmann [this message]
2021-02-03  7:50         ` Arnd Bergmann
2021-02-04  6:55         ` Alistair Francis
2021-02-04  6:55           ` Alistair Francis
2021-01-29  8:07 ` [PATCH v2 1/3] imx7d-remarkable2.dts: Initial device tree for reMarkable2 Shawn Guo

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