Re: [RFC PATCH 2/2] RISC-V: Add basic support for SBI v0.2

From: Atish Patra
Date: Tue Aug 27 2019 - 16:43:19 EST

On Tue, 2019-08-27 at 15:06 +0530, Anup Patel wrote:
> On Tue, Aug 27, 2019 at 5:03 AM Atish Patra <atish.patra@xxxxxxx>
> wrote:
> > The SBI v0.2 introduces a base extension which is backward
> > compatible
> > with v0.1. Implement all helper functions and minimum required SBI
> > calls from v0.2 for now. All other base extension function will be
> > added later as per need.
> >
> > Signed-off-by: Atish Patra <atish.patra@xxxxxxx>
> > ---
> > arch/riscv/include/asm/sbi.h | 68 +++++++++++++++++++++++++++++---
> > ----
> > arch/riscv/kernel/Makefile | 1 +
> > arch/riscv/kernel/sbi.c | 50 ++++++++++++++++++++++++++
> > arch/riscv/kernel/setup.c | 2 ++
> > 4 files changed, 108 insertions(+), 13 deletions(-)
> > create mode 100644 arch/riscv/kernel/sbi.c
> >
> > diff --git a/arch/riscv/include/asm/sbi.h
> > b/arch/riscv/include/asm/sbi.h
> > index 7f5ecaaaa0d7..4a4476956693 100644
> > --- a/arch/riscv/include/asm/sbi.h
> > +++ b/arch/riscv/include/asm/sbi.h
> > @@ -8,7 +8,6 @@
> >
> > #include <linux/types.h>
> >
> > -
> > #define SBI_EXT_LEGACY_SET_TIMER 0x0
> > #define SBI_EXT_LEGACY_CONSOLE_PUTCHAR 0x1
> > #define SBI_EXT_LEGACY_CONSOLE_GETCHAR 0x2
> > @@ -19,28 +18,61 @@
> > #define SBI_EXT_LEGACY_REMOTE_SFENCE_VMA_ASID 0x7
> > #define SBI_EXT_LEGACY_SHUTDOWN 0x8
> >
> > -#define SBI_CALL_LEGACY(which, arg0, arg1, arg2, arg3)
> > ({ \
> > +#define SBI_EXT_BASE 0x10
> > +
> > +enum sbi_ext_base_fid {
> > + SBI_EXT_BASE_GET_SPEC_VERSION = 0,
> > + SBI_EXT_BASE_GET_IMP_ID,
> > + SBI_EXT_BASE_GET_IMP_VERSION,
> > + SBI_EXT_BASE_PROBE_EXT,
> > + SBI_EXT_BASE_GET_MVENDORID,
> > + SBI_EXT_BASE_GET_MARCHID,
> > + SBI_EXT_BASE_GET_MIMPID,
> > +};
> > +
> > +#define SBI_CALL_LEGACY(ext, fid, arg0, arg1, arg2, arg3) ({ \
> > register uintptr_t a0 asm ("a0") = (uintptr_t)(arg0); \
> > register uintptr_t a1 asm ("a1") = (uintptr_t)(arg1); \
> > register uintptr_t a2 asm ("a2") = (uintptr_t)(arg2); \
> > register uintptr_t a3 asm ("a3") = (uintptr_t)(arg3); \
> > - register uintptr_t a7 asm ("a7") = (uintptr_t)(which); \
> > + register uintptr_t a6 asm ("a6") = (uintptr_t)(fid); \
> > + register uintptr_t a7 asm ("a7") = (uintptr_t)(ext); \
> > asm volatile ("ecall" \
> > - : "+r" (a0) \
> > - : "r" (a1), "r" (a2), "r" (a3), "r" (a7) \
> > + : "+r" (a0), "+r" (a1) \
> > + : "r" (a2), "r" (a3), "r" (a6), "r" (a7) \
> > : "memory"); \
> > a0; \
> > })
>
> I think instead of removing old convention we should use
> calling convention based on sbi_version detected at boot-time.
>
> > /* Lazy implementations until SBI is finalized */
> > -#define SBI_CALL_LEGACY_0(which) SBI_CALL_LEGACY(which, 0, 0, 0,
> > 0)
> > -#define SBI_CALL_LEGACY_1(which, arg0) SBI_CALL_LEGACY(which,
> > arg0, 0, 0, 0)
> > -#define SBI_CALL_LEGACY_2(which, arg0, arg1) \
> > - SBI_CALL_LEGACY(which, arg0, arg1, 0, 0)
> > -#define SBI_CALL_LEGACY_3(which, arg0, arg1, arg2) \
> > - SBI_CALL_LEGACY(which, arg0, arg1, arg2, 0)
> > -#define SBI_CALL_LEGACY_4(which, arg0, arg1, arg2, arg3) \
> > - SBI_CALL_LEGACY(which, arg0, arg1, arg2, arg3)
> > +#define SBI_CALL_LEGACY_0(ext) SBI_CALL_LEGACY(ext, 0, 0, 0, 0, 0)
> > +#define SBI_CALL_LEGACY_1(ext, arg0) SBI_CALL_LEGACY(ext, 0, arg0,
> > 0, 0, 0)
> > +#define SBI_CALL_LEGACY_2(ext, arg0, arg1) \
> > + SBI_CALL_LEGACY(ext, 0, arg0, arg1, 0, 0)
> > +#define SBI_CALL_LEGACY_3(ext, arg0, arg1, arg2) \
> > + SBI_CALL_LEGACY(ext, 0, arg0, arg1, arg2, 0)
> > +#define SBI_CALL_LEGACY_4(ext, arg0, arg1, arg2, arg3) \
> > + SBI_CALL_LEGACY(ext, 0, arg0, arg1, arg2, arg3)
> > +
> > +extern unsigned long sbi_firmware_version;
> > +struct sbiret {
> > + long error;
> > + long value;
> > +};
> > +
> > +void riscv_sbi_init(void);
> > +struct sbiret riscv_sbi_ecall(int ext, int fid, int arg0, int
> > arg1,
> > + int arg2, int arg3);
> > +
> > +#define SBI_CALL_0(ext, fid) riscv_sbi_ecall(ext, fid, 0, 0, 0, 0)
> > +#define SBI_CALL_1(ext, fid, arg0) riscv_sbi_ecall(ext, fid, arg0,
> > 0, 0, 0)
> > +#define SBI_CALL_2(ext, fid, arg0, arg1) \
> > + riscv_sbi_ecall(ext, fid, arg0, arg1, 0, 0)
> > +#define SBI_CALL_3(ext, fid, arg0, arg1, arg2) \
> > + riscv_sbi_ecall(ext, fid, arg0, arg1, arg2, 0)
> > +#define SBI_CALL_4(ext, fid, arg0, arg1, arg2, arg3) \
> > + riscv_sbi_ecall(ext, fid, arg0, arg1, arg2, arg3)
> > +
> >
> > static inline void sbi_console_putchar(int ch)
> > {
> > @@ -99,4 +131,14 @@ static inline void
> > sbi_remote_sfence_vma_asid(const unsigned long *hart_mask,
> > start, size, asid);
> > }
>
> To be sure that new kernels work fine on older kernel, we
> can be conservative and move all legacy SBI calls to kernel/sbi.c.
> All legacy SBI calls can check sbi_version and use appropriate
> SBI calling convention.
>
> This might be redundant if we can ensure that newer kernels
> work fine with older SBI v0.1 firmwares.

Yes that's why I didnot want to do it first time. How about this ?

Use only 0.2 convention only and get rid of the 0.1 convention. As it
is anyways backward compatible with 0.1, we don't need a if else
clause.

The legacy calls will not use any value set in a1 and always set 0 in
function id (a6).

>
> > +static inline unsigned long riscv_sbi_major_version(void)
> > +{
> > + return (sbi_firmware_version >> 24) & 0x7f;
> > +}
> > +
> > +static inline unsigned long riscv_sbi_minor_version(void)
> > +{
> > + return sbi_firmware_version & 0xffffff;
> > +}
> > +
> > #endif
> > diff --git a/arch/riscv/kernel/Makefile
> > b/arch/riscv/kernel/Makefile
> > index 2420d37d96de..faf862d26924 100644
> > --- a/arch/riscv/kernel/Makefile
> > +++ b/arch/riscv/kernel/Makefile
> > @@ -17,6 +17,7 @@ obj-y += irq.o
> > obj-y += process.o
> > obj-y += ptrace.o
> > obj-y += reset.o
> > +obj-y += sbi.o
> > obj-y += setup.o
> > obj-y += signal.o
> > obj-y += syscall_table.o
> > diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
> > new file mode 100644
> > index 000000000000..457b8cc0e9d9
> > --- /dev/null
> > +++ b/arch/riscv/kernel/sbi.c
> > @@ -0,0 +1,50 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * SBI initialilization and base extension implementation.
> > + *
> > + * Copyright (c) 2019 Western Digital Corporation or its
> > affiliates.
> > + */
> > +
> > +#include <asm/sbi.h>
> > +#include <linux/sched.h>
> > +
> > +unsigned long sbi_firmware_version;
>
> Rename this too sbi_version or sbi_spec_version.
> The firmware version is different thing.
>

ok.

> > +
> > +struct sbiret riscv_sbi_ecall(int ext, int fid, int arg0, int
> > arg1,
> > + int arg2, int arg3)
> > +{
> > + struct sbiret ret;
> > +
> > + register uintptr_t a0 asm ("a0") = (uintptr_t)(arg0);
> > + register uintptr_t a1 asm ("a1") = (uintptr_t)(arg1);
> > + register uintptr_t a2 asm ("a2") = (uintptr_t)(arg2);
> > + register uintptr_t a3 asm ("a3") = (uintptr_t)(arg3);
> > + register uintptr_t a6 asm ("a6") = (uintptr_t)(fid);
> > + register uintptr_t a7 asm ("a7") = (uintptr_t)(ext);
> > + asm volatile ("ecall"
> > + : "+r" (a0), "+r" (a1)
> > + : "r" (a2), "r" (a3), "r" (a6), "r" (a7)
> > + : "memory");
> > + ret.error = a0;
> > + ret.value = a1;
> > +
> > + return ret;
> > +}
> > +
> > +static struct sbiret sbi_get_spec_version(void)
> > +{
> > + return SBI_CALL_0(SBI_EXT_BASE,
> > SBI_EXT_BASE_GET_SPEC_VERSION);
> > +}
> > +
> > +void riscv_sbi_init(void)
> > +{
> > + struct sbiret ret;
> > +
> > + /* legacy SBI version*/
> > + sbi_firmware_version = 0x1;
> > + ret = sbi_get_spec_version();
> > + if (!ret.error)
> > + sbi_firmware_version = ret.value;
> > + pr_info("SBI version implemented in firmware [%lu:%lu]\n",
> > + riscv_sbi_major_version(),
> > riscv_sbi_minor_version());
>
> Should we not print SBI implementation ID and SBI firmware version.
>

Eventually yes. I wanted to have this series minimal implementation and
build upon it.

I will go ahead and add those.

> Regards,
> Anup
>
> > +}
> > diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> > index a990a6cb184f..4c324fd398c8 100644
> > --- a/arch/riscv/kernel/setup.c
> > +++ b/arch/riscv/kernel/setup.c
> > @@ -21,6 +21,7 @@
> > #include <asm/sections.h>
> > #include <asm/pgtable.h>
> > #include <asm/smp.h>
> > +#include <asm/sbi.h>
> > #include <asm/tlbflush.h>
> > #include <asm/thread_info.h>
> >
> > @@ -70,6 +71,7 @@ void __init setup_arch(char **cmdline_p)
> > swiotlb_init(1);
> > #endif
> >
> > + riscv_sbi_init();
> > #ifdef CONFIG_SMP
> > setup_smp();
> > #endif
> > --
> > 2.21.0
> >

--
Regards,
Atish