Excerpts from Paul Mackerras's message of June 18, 2021 1:43 pm:
> Microwatt is a FPGA-based implementation of the Power ISA. It
> currently only implements little-endian 64-bit mode, and does
> not (yet) support SMP, VMX, VSX or transactional memory. It has an
> optional FPU, and an optional MMU (required for running Linux,
> obviously) which implements a configurable radix tree but not
> hypervisor mode or nested radix translation.
>
> This adds a new machine type to support FPGA-based SoCs with a
> Microwatt core. CONFIG_MATH_EMULATION can be selected for Microwatt
> SOCs which don't have the FPU.
The only thing I can think of is you may want to select PPC_RADIX and
other possible things that are required, but that's not a big deal at
the moment. I have a few kernel size reduction config patches (like
CONFIG_PPC_HASH) I might be able to upstream now for Microwatt, so I
could do a bit of a pass over the Kconfig stuff at that point.
Reviewed-by: Nicholas Piggin <npig...@gmail.com>
>
> Signed-off-by: Paul Mackerras <pau...@ozlabs.org>
> ---
> arch/powerpc/Kconfig | 2 +-
> arch/powerpc/platforms/Kconfig | 1 +
> arch/powerpc/platforms/Makefile | 1 +
> arch/powerpc/platforms/microwatt/Kconfig | 9 +++++++++
> arch/powerpc/platforms/microwatt/Makefile | 1 +
> arch/powerpc/platforms/microwatt/setup.c | 23 +++++++++++++++++++++++
> 6 files changed, 36 insertions(+), 1 deletion(-)
> create mode 100644 arch/powerpc/platforms/microwatt/Kconfig
> create mode 100644 arch/powerpc/platforms/microwatt/Makefile
> create mode 100644 arch/powerpc/platforms/microwatt/setup.c
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 386ae12d8523..5ce51c38a346 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -422,7 +422,7 @@ config HUGETLB_PAGE_SIZE_VARIABLE
>
> config MATH_EMULATION
> bool "Math emulation"
> - depends on 4xx || PPC_8xx || PPC_MPC832x || BOOKE
> + depends on 4xx || PPC_8xx || PPC_MPC832x || BOOKE || PPC_MICROWATT
> select PPC_FPU_REGS
> help
> Some PowerPC chips designed for embedded applications do not have
> diff --git a/arch/powerpc/platforms/Kconfig b/arch/powerpc/platforms/Kconfig
> index 7a5e8f4541e3..74be4d06afbf 100644
> --- a/arch/powerpc/platforms/Kconfig
> +++ b/arch/powerpc/platforms/Kconfig
> @@ -20,6 +20,7 @@ source "arch/powerpc/platforms/embedded6xx/Kconfig"
> source "arch/powerpc/platforms/44x/Kconfig"
> source "arch/powerpc/platforms/40x/Kconfig"
> source "arch/powerpc/platforms/amigaone/Kconfig"
> +source "arch/powerpc/platforms/microwatt/Kconfig"
>
> config KVM_GUEST
> bool "KVM Guest support"
> diff --git a/arch/powerpc/platforms/Makefile b/arch/powerpc/platforms/Makefile
> index 143d4417f6cc..edcb54cdb1a8 100644
> --- a/arch/powerpc/platforms/Makefile
> +++ b/arch/powerpc/platforms/Makefile
> @@ -22,3 +22,4 @@ obj-$(CONFIG_PPC_CELL) += cell/
> obj-$(CONFIG_PPC_PS3) += ps3/
> obj-$(CONFIG_EMBEDDED6xx) += embedded6xx/
> obj-$(CONFIG_AMIGAONE) += amigaone/
> +obj-$(CONFIG_PPC_MICROWATT) += microwatt/
> diff --git a/arch/powerpc/platforms/microwatt/Kconfig
> b/arch/powerpc/platforms/microwatt/Kconfig
> new file mode 100644
> index 000000000000..3be01e78ce57
> --- /dev/null
> +++ b/arch/powerpc/platforms/microwatt/Kconfig
> @@ -0,0 +1,9 @@
> +# SPDX-License-Identifier: GPL-2.0
> +config PPC_MICROWATT
> + depends on PPC_BOOK3S_64 && !SMP
> + bool "Microwatt SoC platform"
> + select PPC_XICS
> + select PPC_NATIVE
> + help
> + This option enables support for FPGA-based Microwatt
> implementations.
> +
> diff --git a/arch/powerpc/platforms/microwatt/Makefile
> b/arch/powerpc/platforms/microwatt/Makefile
> new file mode 100644
> index 000000000000..e6885b3b2ee7
> --- /dev/null
> +++ b/arch/powerpc/platforms/microwatt/Makefile
> @@ -0,0 +1 @@
> +obj-y += setup.o
> diff --git a/arch/powerpc/platforms/microwatt/setup.c
> b/arch/powerpc/platforms/microwatt/setup.c
> new file mode 100644
> index 000000000000..d80d52612672
> --- /dev/null
> +++ b/arch/powerpc/platforms/microwatt/setup.c
> @@ -0,0 +1,23 @@
> +/*
> + * Microwatt FPGA-based SoC platform setup code.
> + *
> + * Copyright 2020 Paul Mackerras (pau...@ozlabs.org), IBM Corp.
> + */
> +
> +#include <linux/types.h>
> +#include <linux/kernel.h>
> +#include <linux/stddef.h>
> +#include <linux/init.h>
> +#include <asm/machdep.h>
> +#include <asm/time.h>
> +
> +static int __init microwatt_probe(void)
> +{
> + return of_machine_is_compatible("microwatt-soc");
> +}
> +
> +define_machine(microwatt) {
> + .name = "microwatt",
> + .probe = microwatt_probe,
> + .calibrate_decr = generic_calibrate_decr,
> +};
> --
> 2.31.1
>
>
