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Date:   Wed, 28 Aug 2019 14:37:33 -0700 (PDT)
Subject:     Re: [RFC PATCH 1/2] RISC-V: Mark existing SBI as legacy SBI.
In-Reply-To: <20190827083700.GF682@rapoport-lnx>
CC:     anup@brainfault.org, aou@eecs.berkeley.edu, alankao@andestech.com,
        alexios.zavras@intel.com, Greg KH <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org, Atish Patra <Atish.Patra@wdc.com>,
        gary@garyguo.net, Paul Walmsley <paul.walmsley@sifive.com>,
        linux-riscv@lists.infradead.org, tglx@linutronix.de
From:   Palmer Dabbelt <palmer@sifive.com>
To:     rppt@linux.ibm.com
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On Tue, 27 Aug 2019 01:37:00 PDT (-0700), rppt@linux.ibm.com wrote:
> On Tue, Aug 27, 2019 at 01:58:03PM +0530, Anup Patel wrote:
>> On Tue, Aug 27, 2019 at 1:21 PM Mike Rapoport <rppt@linux.ibm.com> wrote:
>> >
>> > On Mon, Aug 26, 2019 at 04:32:55PM -0700, Atish Patra wrote:
>> > > As per the new SBI specification, current SBI implementation is
>> > > defined as legacy and will be removed/replaced in future.
>> > >
>> > > Rename existing implementation to reflect that. This patch is just
>> > > a preparatory patch for SBI v0.2 and doesn't introduce any functional
>> > > changes.
>> > >
>> > > Signed-off-by: Atish Patra <atish.patra@wdc.com>
>> > > ---
>> > >  arch/riscv/include/asm/sbi.h | 61 +++++++++++++++++++-----------------
>> > >  1 file changed, 33 insertions(+), 28 deletions(-)
>> > >
>> > > diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
>> > > index 21134b3ef404..7f5ecaaaa0d7 100644
>> > > --- a/arch/riscv/include/asm/sbi.h
>> > > +++ b/arch/riscv/include/asm/sbi.h
>> > > @@ -8,17 +8,18 @@
>> > >
>> > >  #include <linux/types.h>
>> > >
>> > > -#define SBI_SET_TIMER 0
>> > > -#define SBI_CONSOLE_PUTCHAR 1
>> > > -#define SBI_CONSOLE_GETCHAR 2
>> > > -#define SBI_CLEAR_IPI 3
>> > > -#define SBI_SEND_IPI 4
>> > > -#define SBI_REMOTE_FENCE_I 5
>> > > -#define SBI_REMOTE_SFENCE_VMA 6
>> > > -#define SBI_REMOTE_SFENCE_VMA_ASID 7
>> > > -#define SBI_SHUTDOWN 8
>> > > -
>> > > -#define SBI_CALL(which, arg0, arg1, arg2, arg3) ({           \
>> > > +
>> > > +#define SBI_EXT_LEGACY_SET_TIMER 0x0
>> > > +#define SBI_EXT_LEGACY_CONSOLE_PUTCHAR 0x1
>> > > +#define SBI_EXT_LEGACY_CONSOLE_GETCHAR 0x2
>> > > +#define SBI_EXT_LEGACY_CLEAR_IPI 0x3
>> > > +#define SBI_EXT_LEGACY_SEND_IPI 0x4
>> > > +#define SBI_EXT_LEGACY_REMOTE_FENCE_I 0x5
>> > > +#define SBI_EXT_LEGACY_REMOTE_SFENCE_VMA 0x6
>> > > +#define SBI_EXT_LEGACY_REMOTE_SFENCE_VMA_ASID 0x7
>> > > +#define SBI_EXT_LEGACY_SHUTDOWN 0x8
>> >
>> > I can't say I'm closely following RISC-V development, but what will happen
>> > when SBI v0.3 will come out and will render v0.2 legacy?
>> > Won't we need another similar renaming then?
>>
>> Going forward with SBI v0.3 and higher, we won't see any calling
>> convention changes.
>>
>> The SBI spec will be maintained and improved by RISC-V UNIX
>> platform spec working group.
>>
>> My best guess is that, all future SBI releases (v0.3 or higher) will
>> include more optional SBI extensions (hart hotplug, power management, etc).
>
> Thanks for the clarification!

Specifically the issue is that 0.1 didn't include any mechanism for probing the 
existence of a function, but since that has been added in 0.2 it's possible to 
maintain compatible with future versions.

>
>> Regards,
>> Anup
>>
>> >
>> > > +#define SBI_CALL_LEGACY(which, 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);   \
>> > > @@ -32,58 +33,61 @@
>> > >  })
>> > >
>> > >  /* Lazy implementations until SBI is finalized */
>> > > -#define SBI_CALL_0(which) SBI_CALL(which, 0, 0, 0, 0)
>> > > -#define SBI_CALL_1(which, arg0) SBI_CALL(which, arg0, 0, 0, 0)
>> > > -#define SBI_CALL_2(which, arg0, arg1) SBI_CALL(which, arg0, arg1, 0, 0)
>> > > -#define SBI_CALL_3(which, arg0, arg1, arg2) \
>> > > -             SBI_CALL(which, arg0, arg1, arg2, 0)
>> > > -#define SBI_CALL_4(which, arg0, arg1, arg2, arg3) \
>> > > -             SBI_CALL(which, arg0, arg1, arg2, arg3)
>> > > +#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)
>> > >
>> > >  static inline void sbi_console_putchar(int ch)
>> > >  {
>> > > -     SBI_CALL_1(SBI_CONSOLE_PUTCHAR, ch);
>> > > +     SBI_CALL_LEGACY_1(SBI_EXT_LEGACY_CONSOLE_PUTCHAR, ch);
>> > >  }
>> > >
>> > >  static inline int sbi_console_getchar(void)
>> > >  {
>> > > -     return SBI_CALL_0(SBI_CONSOLE_GETCHAR);
>> > > +     return SBI_CALL_LEGACY_0(SBI_EXT_LEGACY_CONSOLE_GETCHAR);
>> > >  }
>> > >
>> > >  static inline void sbi_set_timer(uint64_t stime_value)
>> > >  {
>> > >  #if __riscv_xlen == 32
>> > > -     SBI_CALL_2(SBI_SET_TIMER, stime_value, stime_value >> 32);
>> > > +     SBI_CALL_LEGACY_2(SBI_EXT_LEGACY_SET_TIMER, stime_value,
>> > > +                       stime_value >> 32);
>> > >  #else
>> > > -     SBI_CALL_1(SBI_SET_TIMER, stime_value);
>> > > +     SBI_CALL_LEGACY_1(SBI_EXT_LEGACY_SET_TIMER, stime_value);
>> > >  #endif
>> > >  }
>> > >
>> > >  static inline void sbi_shutdown(void)
>> > >  {
>> > > -     SBI_CALL_0(SBI_SHUTDOWN);
>> > > +     SBI_CALL_LEGACY_0(SBI_EXT_LEGACY_SHUTDOWN);
>> > >  }
>> > >
>> > >  static inline void sbi_clear_ipi(void)
>> > >  {
>> > > -     SBI_CALL_0(SBI_CLEAR_IPI);
>> > > +     SBI_CALL_LEGACY_0(SBI_EXT_LEGACY_CLEAR_IPI);
>> > >  }
>> > >
>> > >  static inline void sbi_send_ipi(const unsigned long *hart_mask)
>> > >  {
>> > > -     SBI_CALL_1(SBI_SEND_IPI, hart_mask);
>> > > +     SBI_CALL_LEGACY_1(SBI_EXT_LEGACY_SEND_IPI, hart_mask);
>> > >  }
>> > >
>> > >  static inline void sbi_remote_fence_i(const unsigned long *hart_mask)
>> > >  {
>> > > -     SBI_CALL_1(SBI_REMOTE_FENCE_I, hart_mask);
>> > > +     SBI_CALL_LEGACY_1(SBI_EXT_LEGACY_REMOTE_FENCE_I, hart_mask);
>> > >  }
>> > >
>> > >  static inline void sbi_remote_sfence_vma(const unsigned long *hart_mask,
>> > >                                        unsigned long start,
>> > >                                        unsigned long size)
>> > >  {
>> > > -     SBI_CALL_3(SBI_REMOTE_SFENCE_VMA, hart_mask, start, size);
>> > > +     SBI_CALL_LEGACY_3(SBI_EXT_LEGACY_REMOTE_SFENCE_VMA, hart_mask,
>> > > +                       start, size);
>> > >  }
>> > >
>> > >  static inline void sbi_remote_sfence_vma_asid(const unsigned long *hart_mask,
>> > > @@ -91,7 +95,8 @@ static inline void sbi_remote_sfence_vma_asid(const unsigned long *hart_mask,
>> > >                                             unsigned long size,
>> > >                                             unsigned long asid)
>> > >  {
>> > > -     SBI_CALL_4(SBI_REMOTE_SFENCE_VMA_ASID, hart_mask, start, size, asid);
>> > > +     SBI_CALL_LEGACY_4(SBI_EXT_LEGACY_REMOTE_SFENCE_VMA_ASID, hart_mask,
>> > > +                       start, size, asid);
>> > >  }
>> > >
>> > >  #endif
>> > > --
>> > > 2.21.0
>> > >
>> > >
>> > > _______________________________________________
>> > > linux-riscv mailing list
>> > > linux-riscv@lists.infradead.org
>> > > http://lists.infradead.org/mailman/listinfo/linux-riscv
>> > >
>> >
>> > --
>> > Sincerely yours,
>> > Mike.
>> >
>> >
>> > _______________________________________________
>> > linux-riscv mailing list
>> > linux-riscv@lists.infradead.org
>> > http://lists.infradead.org/mailman/listinfo/linux-riscv
>>
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