[RFC PATCH] platform: generic: thead: add sfence workaroud for th1520/sg2042
Icenowy Zheng
uwu at icenowy.me
Tue Sep 12 23:41:48 PDT 2023
在 2023-09-13星期三的 06:18 +0100，Jessica Clarke写道：
> On 13 Sep 2023, at 06:08, Inochi Amaoto <inochiama at outlook.com>
> wrote:
> >
> > As the mmu of T-HEAD th1520 and Sophgo sg2042 is still functional
> > after
> > switching opensbi,
>
> “MMU is still functional after switching OpenSBI”? What does that
> mean?
As what I heard from T-Head, it's some stale TLB entries that still
affect M mode.
>
> > so they need to execute sfence.vma in the trap handler to
> > function properly.
> >
> > To handle this workaroud, add a degraded alternative mechanism in
> > the thead
> > platform to patch the trap handler.
>
> Don’t mess up generic code for this, just override the trap handler
> and
> branch to the generic one after whatever workaround you supposedly
> need
> for unclear reasons?
Could the trap handler be overriden easily?
>
> But this needs a much clearer explanation of whatever’s going on
> here,
> which sounds like a spec violation being described to me. What
> exactly
> is the hardware erratum and where is it documented?
>
> Jess
>
> > Signed-off-by: Inochi Amaoto <inochiama at outlook.com>
> > ---
> > firmware/fw_base.S | 9 ++++
> > platform/generic/Kconfig | 4 ++
> > platform/generic/configs/defconfig | 1 +
> > platform/generic/thead/objects.mk | 10 +++++
> > platform/generic/thead/thead-generic.c | 62
> > ++++++++++++++++++++++++++
> > platform/generic/thead/thead-patch.S | 28 ++++++++++++
> > 6 files changed, 114 insertions(+)
> > create mode 100644 platform/generic/thead/objects.mk
> > create mode 100644 platform/generic/thead/thead-generic.c
> > create mode 100644 platform/generic/thead/thead-patch.S
> >
> > diff --git a/firmware/fw_base.S b/firmware/fw_base.S
> > index ca34b4c..80aa0a3 100644
> > --- a/firmware/fw_base.S
> > +++ b/firmware/fw_base.S
> > @@ -760,6 +760,15 @@ memcmp:
> > .globl _trap_handler
> > .globl _trap_exit
> > _trap_handler:
> > + /* pile for T-HEAD sfence workaround, nop for otherwise */
> > + .option push
> > + .option norvc
> > + .option norelax
> > +
> > + nop
> > +
> > + .option pop
> > +
> > TRAP_SAVE_AND_SETUP_SP_T0
> >
> > TRAP_SAVE_MEPC_MSTATUS 0
> > diff --git a/platform/generic/Kconfig b/platform/generic/Kconfig
> > index 72768ed..68dd58c 100644
> > --- a/platform/generic/Kconfig
> > +++ b/platform/generic/Kconfig
> > @@ -52,6 +52,10 @@ config PLATFORM_STARFIVE_JH7110
> > bool "StarFive JH7110 support"
> > default n
> >
> > +config PLATFORM_THEAD_GENERIC
> > + bool "THEAD C9xx generic platform support"
> > + default n
> > +
> > source "$(OPENSBI_SRC_DIR)/platform/generic/andes/Kconfig"
> >
> > endif
> > diff --git a/platform/generic/configs/defconfig
> > b/platform/generic/configs/defconfig
> > index 634d410..26f0874 100644
> > --- a/platform/generic/configs/defconfig
> > +++ b/platform/generic/configs/defconfig
> > @@ -4,6 +4,7 @@ CONFIG_PLATFORM_RENESAS_RZFIVE=y
> > CONFIG_PLATFORM_SIFIVE_FU540=y
> > CONFIG_PLATFORM_SIFIVE_FU740=y
> > CONFIG_PLATFORM_STARFIVE_JH7110=y
> > +CONFIG_PLATFORM_THEAD_GENERIC=y
> > CONFIG_FDT_GPIO=y
> > CONFIG_FDT_GPIO_DESIGNWARE=y
> > CONFIG_FDT_GPIO_SIFIVE=y
> > diff --git a/platform/generic/thead/objects.mk
> > b/platform/generic/thead/objects.mk
> > new file mode 100644
> > index 0000000..78a2a79
> > --- /dev/null
> > +++ b/platform/generic/thead/objects.mk
> > @@ -0,0 +1,10 @@
> > +#
> > +# SPDX-License-Identifier: BSD-2-Clause
> > +#
> > +# Copyright (C) 2023 Inochi Amaoto <inochiama at outlook.com>
> > +# Copyright (C) 2023 Alibaba Group Holding Limited.
> > +#
> > +
> > +carray-platform_override_modules-$(CONFIG_PLATFORM_THEAD_GENERIC)
> > += thead_generic
> > +platform-objs-$(CONFIG_PLATFORM_THEAD_GENERIC) += thead/thead-
> > generic.o
> > +platform-objs-$(CONFIG_PLATFORM_THEAD_GENERIC) += thead/thead-
> > patch.o
> > diff --git a/platform/generic/thead/thead-generic.c
> > b/platform/generic/thead/thead-generic.c
> > new file mode 100644
> > index 0000000..2755ae2
> > --- /dev/null
> > +++ b/platform/generic/thead/thead-generic.c
> > @@ -0,0 +1,62 @@
> > +/*
> > + * SPDX-License-Identifier: BSD-2-Clause
> > + *
> > + * Authors:
> > + * Inochi Amaoto <inochiama at outlook.com>
> > + *
> > + */
> > +
> > +#include <platform_override.h>
> > +#include <sbi/riscv_barrier.h>
> > +#include <sbi/sbi_const.h>
> > +#include <sbi/sbi_platform.h>
> > +#include <sbi/sbi_scratch.h>
> > +#include <sbi/sbi_string.h>
> > +#include <sbi_utils/fdt/fdt_helper.h>
> > +
> > +#define THEAD_QUIRK_SFENCE_FIXUP BIT(0)
> > +
> > +#define thead_get_symbol_local_address(_name) \
> > + ({ \
> > + register unsigned long __v; \
> > + __asm__ __volatile__ ("lla %0, " STRINGIFY(_name) \
> > + : "=r"(__v) \
> > + : \
> > + : "memory"); \
> > + (void*)__v; \
> > + })
> > +
> > +extern const unsigned int thead_patch_sfence_size;
> > +
> > +void thead_fixup_sfence(void)
> > +{
> > + void* trap_addr = thead_get_symbol_local_address(_trap_handler);
> > + void* patch_addr =
> > thead_get_symbol_local_address(thead_patch_sfence);
> > +
> > + sbi_memcpy(trap_addr, patch_addr, thead_patch_sfence_size);
> > + RISCV_FENCE_I;
> > +}
> > +
> > +static int thead_generic_early_init(bool cold_boot, const struct
> > fdt_match *match)
> > +{
> > + unsigned long quirks = (unsigned long)match->data;
> > +
> > + if (cold_boot) {
> > + if (quirks & THEAD_QUIRK_SFENCE_FIXUP) {
> > + thead_fixup_sfence();
> > + }
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static const struct fdt_match thead_generic_match[] = {
> > + { .compatible = "thead,th1520",
> > + .data = (void*)THEAD_QUIRK_SFENCE_FIXUP },
> > + { },
> > +};
> > +
> > +const struct platform_override thead_generic = {
> > + .match_table = thead_generic_match,
> > + .early_init = thead_generic_early_init,
> > +};
> > diff --git a/platform/generic/thead/thead-patch.S
> > b/platform/generic/thead/thead-patch.S
> > new file mode 100644
> > index 0000000..6921b1c
> > --- /dev/null
> > +++ b/platform/generic/thead/thead-patch.S
> > @@ -0,0 +1,28 @@
> > +/*
> > + * SPDX-License-Identifier: BSD-2-Clause
> > + *
> > + * Authors:
> > + * Inochi Amaoto <inochiama at outlook.com>
> > + *
> > + */
> > +
> > +#include <sbi/riscv_elf.h>
> > +
> > + .section .entry, "ax", %progbits
> > + .align 3
> > + .globl thead_patch_sfence
> > +thead_patch_sfence:
> > + .option push
> > + .option norvc
> > + .option norelax
> > +
> > + sfence.vma zero, t0
> > +
> > + .option pop
> > +.equ _thead_patch_sfence_size, . - thead_patch_sfence
> > +
> > + .section .rodata
> > + .align 3
> > + .globl thead_patch_sfence_size
> > +thead_patch_sfence_size:
> > + RISCV_INT _thead_patch_sfence_size
> > --
> > 2.42.0
> >
> >
> > --
> > opensbi mailing list
> > opensbi at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/opensbi
>
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