Re: [RFC] ARM: add multi_v7_lpae_defconfig

[Arnd Bergmann <arnd@arndb.de>]

On Fri, Jan 10, 2020 at 6:35 PM Nicolas Saenz Julienne
<nsaenzjulienne@suse.de> wrote:
>
> 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 configurations.
>
> Note that merge_into_defconfig was taken from arch/powerpc/Makefile.
>
> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>

I like the idea, but I would note that a lot of platforms enabled in
multi_v7_defconfig do not support LPAE. In particular, the first ARMv7
cores (Cortex-A8, -A9, -A5, and PJ4) don't, but the later ones (Cortex-A7,
-A15, -A17, and PJ4C-MP) do.

Here is a list from the defconfig file

CONFIG_ARCH_VIRT=y
CONFIG_ARCH_ALPINE=y
CONFIG_ARCH_ARTPEC=y
CONFIG_MACH_ARTPEC6=y

Artpec is A9

CONFIG_ARCH_ASPEED=y
CONFIG_MACH_ASPEED_G6=y
CONFIG_ARCH_AT91=y
CONFIG_SOC_SAMA5D2=y
CONFIG_SOC_SAMA5D3=y
CONFIG_SOC_SAMA5D4=y

AT91/SAMA5 is A5

CONFIG_ARCH_BCM=y
CONFIG_ARCH_BCM_CYGNUS=y
CONFIG_ARCH_BCM_HR2=y
CONFIG_ARCH_BCM_NSP=y
CONFIG_ARCH_BCM_5301X=y
CONFIG_ARCH_BCM_281XX=y
CONFIG_ARCH_BCM_21664=y
CONFIG_ARCH_BCM_63XX=y
CONFIG_ARCH_BRCMSTB=y

I think most of the above are A9, but not sure

CONFIG_ARCH_BCM2835=y
CONFIG_ARCH_BERLIN=y
CONFIG_MACH_BERLIN_BG2CD=y
CONFIG_MACH_BERLIN_BG2Q=y
CONFIG_MACH_BERLIN_BG2=y

These are mixed, I think BG2CD is A7, but the older ones are A9 or PJ4

CONFIG_ARCH_DIGICOLOR=y

CX92755 is an A8

CONFIG_ARCH_EXYNOS=y

exynos is a mix of A9 and A15/A7, so this is fine

CONFIG_ARCH_HIGHBANK=y

A9 and A15, also fine

CONFIG_ARCH_HISI=y
CONFIG_ARCH_HI3xxx=y
CONFIG_ARCH_HIP01=y
CONFIG_ARCH_HIP04=y
CONFIG_ARCH_HIX5HD2=y
CONFIG_ARCH_MXC=y
CONFIG_SOC_IMX50=y
CONFIG_SOC_IMX51=y
CONFIG_SOC_IMX53=y

IMX5 is A8

CONFIG_SOC_IMX6Q=y
CONFIG_SOC_IMX6SL=y
CONFIG_SOC_IMX6SX=y

These older imx6 variants are A9, but the 6UL and 7D are A7.

CONFIG_SOC_IMX6UL=y
CONFIG_SOC_LS1021A=y
CONFIG_SOC_IMX7D=y
CONFIG_SOC_VF610=y

VF610 is an A5

CONFIG_ARCH_KEYSTONE=y
CONFIG_ARCH_MEDIATEK=y

Mediatek is mostly A7, but some A9

CONFIG_ARCH_MESON=y

Mixed

CONFIG_ARCH_MILBEAUT=y
CONFIG_ARCH_MILBEAUT_M10V=y
CONFIG_ARCH_MMP=y
CONFIG_MACH_MMP2_DT=y
CONFIG_MACH_MMP3_DT=y

MMP is a PJ4, I don't think there is LPAE, but not sure

CONFIG_ARCH_MVEBU=y
CONFIG_MACH_ARMADA_370=y
CONFIG_MACH_ARMADA_375=y
CONFIG_MACH_ARMADA_38X=y
CONFIG_MACH_ARMADA_39X=y
CONFIG_MACH_ARMADA_XP=y
CONFIG_MACH_DOVE=y

Fairly sure only Armada XP has LPAE out of these

CONFIG_ARCH_OMAP3=y
CONFIG_ARCH_OMAP4=y
CONFIG_SOC_OMAP5=y
CONFIG_SOC_AM33XX=y
CONFIG_SOC_AM43XX=y
CONFIG_SOC_DRA7XX=y

only OMAP5 and DRA7 use an A15, the others are A8 or A9

CONFIG_ARCH_SIRF=y
CONFIG_ARCH_QCOM=y
CONFIG_ARCH_MSM8X60=y
CONFIG_ARCH_MSM8960=y
CONFIG_ARCH_MSM8974=y

Not sure whether there is LPAE on Qualcomm's custom cores

CONFIG_ARCH_ROCKCHIP=y

Mixed

CONFIG_ARCH_RENESAS=y

Mixed

CONFIG_ARCH_SOCFPGA=y

A9 only

CONFIG_PLAT_SPEAR=y
CONFIG_ARCH_SPEAR13XX=y
CONFIG_MACH_SPEAR1310=y
CONFIG_MACH_SPEAR1340=y

A9 only

CONFIG_ARCH_STI=y
CONFIG_ARCH_STM32=y
CONFIG_ARCH_SUNXI=y

sunxi has A8 and A7 (and one that is A15+A7)

CONFIG_ARCH_TEGRA=y

Mixed

CONFIG_ARCH_UNIPHIER=y

 A9 only so far

CONFIG_ARCH_U8500=y

A9 only

CONFIG_ARCH_VEXPRESS=y

A9 or A15

CONFIG_ARCH_WM8850=y

A9

CONFIG_ARCH_ZYNQ=y

A9

I think it would make sense to either turn off the various A8/A9/A5 platforms
in the fragment, or add a CONFIG_ARCH_MULTI_V7VE option, and then
change the Kconfig dependencies so that the older platforms get turned off
when only V7 but not V7VE is set.

      Arnd