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Subject: Re: [RFC] ARM: add bcm2711_defconfig
From:   Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
To:     Florian Fainelli <f.fainelli@gmail.com>,
        Stefan Wahren <wahrenst@gmx.net>
Cc:     mbrugger@suse.com, Russell King <linux@armlinux.org.uk>,
        linux-kernel@vger.kernel.org,
        bcm-kernel-feedback-list@broadcom.com,
        linux-rpi-kernel@lists.infradead.org, hch@lst.de,
        linux-arm-kernel@lists.infradead.org
Date:   Wed, 08 Jan 2020 14:53:22 +0100
In-Reply-To: <5db5ed47-adab-8d31-c3f7-4d7f63258e22@gmail.com>
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On Tue, 2020-01-07 at 10:28 -0800, Florian Fainelli wrote:
> On 1/7/20 10:11 AM, Nicolas Saenz Julienne wrote:
> > On Tue, 2020-01-07 at 19:06 +0100, Stefan Wahren wrote:
> > > Hi Nicolas,
> > >=20
> > > Am 07.01.20 um 18:24 schrieb Nicolas Saenz Julienne:
> > > > The Raspberry Pi 4 depends on LPAE in order to use its PCIe port, w=
hich
> > > > is essential, as it ultimately provides USB2/3 connectivity. As thi=
s
> > > > setup doesn't fit any generic purpose configuration this adds
> > > > bcm2711_defconfig which is based on the current Raspberry Pi founda=
tion
> > > > config file[1] with as little changes as possible
> > >=20
> > > i really dislike the Foundation config file, because it contains so m=
any
> > > unnecessary features. Bisecting with such a kernel config is horrible=
.
> > >=20
> > > How about finding a compromise between bcm2835_defconfig and
> > > multi_v7_defconfig + LPAE?
> >=20
> > If there is a consensus this is the right approach (creating a new conf=
ig
> > file), I'll be happy to try that out.
> >=20
> > Now that I think of it, maybe we shouldn't add bcm2711_thermal into
> > multi_v7_defconfig.
>=20
> It there a mechanism that can be used such that bcm2711_defconfig would
> be simply a fragment that enables CONFIG_ARM_LPAE=3Dy (and other relevant
> 2711 only options) and that you could easily run/test with, something lik=
e:
>=20
> ARCH=3Darm make bcm2835_defconfig+bcm2711_defconfig
>=20
> or something along those lines?

Well I found out about: 'scripts/kconfig/merge_config.sh' which more or les=
s
does that. I think we could use it to build bcm2711_defconfig based off
bcm2835_defconfig. Or even better, create a multi_v7_lpae_defconfig. See:

Author: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Date:   Wed Jan 8 14:30:56 2020 +0100

    ARM: Add multi_v7_lpae_defconfig

    The only missing configuration option preventing us from using
    multi_v7_defconfig with the RPi4 is ARM_LPAE. It's needed as the PCIe
    controller found on the SoC depends on 64bit addressing, yet can't be
    included as not all v7 boards support LPAE.

    Introduce multi_v7_lpae_defconfig, built off multi_v7_defconfig, which =
will
    avoid us having to duplicate and maintain multiple similar configuratio=
ns.

    Note that merge_into_defconfig was taken from arch/powerpc/Makefile.

    Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>

diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 16d41efea7f2..bf6379c718ee 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -359,6 +359,20 @@ archclean:
 # My testing targets (bypasses dependencies)
 bp:;   $(Q)$(MAKE) $(build)=3D$(boot) MACHINE=3D$(MACHINE) $(boot)/bootpIm=
age

+# Used to create 'merged defconfigs'
+# To use it $(call) it with the first argument as the base defconfig
+# and the second argument as a space separated list of .config files to me=
rge,
+# without the .config suffix.
+define merge_into_defconfig
+       $(Q)$(CONFIG_SHELL) $(srctree)/scripts/kconfig/merge_config.sh \
+               -m -O $(objtree) $(srctree)/arch/$(ARCH)/configs/$(1) \
+               $(foreach
config,$(2),$(srctree)/arch/$(ARCH)/configs/$(config).config)
+       +$(Q)$(MAKE) -f $(srctree)/Makefile olddefconfig
+endef
+
+PHONY +=3D multi_v7_lpae_defconfig
+multi_v7_lpae_defconfig:
+       $(call merge_into_defconfig,multi_v7_defconfig,lpae)

 define archhelp
   echo  '* zImage        - Compressed kernel image (arch/$(ARCH)/boot/zIma=
ge)'
diff --git a/arch/arm/configs/lpae.config b/arch/arm/configs/lpae.config
new file mode 100644
index 000000000000..19bab134e014
--- /dev/null
+++ b/arch/arm/configs/lpae.config
@@ -0,0 +1 @@
+CONFIG_ARM_LPAE=3Dy


Any thoughts? Is this a little bit too much?

Regards,
Nicolas


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