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 <20231118033859.726692-3-apatel@ventanamicro.com> <20231120-639982716fbfd33a6fc144d6@orel>
In-Reply-To: <20231120-639982716fbfd33a6fc144d6@orel>
From:   Anup Patel <apatel@ventanamicro.com>
Date:   Thu, 23 Nov 2023 16:17:02 +0530
Message-ID: <CAK9=C2X-cOxjJ-fBLrcvWvP+K8fD=PGucmrWN+m1ZK3j7ae_zg@mail.gmail.com>
Subject: Re: [PATCH v4 2/5] RISC-V: Add SBI debug console helper routines
To:     Andrew Jones <ajones@ventanamicro.com>
Cc:     Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jirislaby@kernel.org>,
        Conor Dooley <conor@kernel.org>,
        linux-riscv@lists.infradead.org, linux-serial@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
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On Mon, Nov 20, 2023 at 1:35=E2=80=AFPM Andrew Jones <ajones@ventanamicro.c=
om> wrote:
>
> On Sat, Nov 18, 2023 at 09:08:56AM +0530, Anup Patel wrote:
> > Let us provide SBI debug console helper routines which can be
> > shared by serial/earlycon-riscv-sbi.c and hvc/hvc_riscv_sbi.c.
> >
> > Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> > ---
> >  arch/riscv/include/asm/sbi.h |  5 +++++
> >  arch/riscv/kernel/sbi.c      | 43 ++++++++++++++++++++++++++++++++++++
> >  2 files changed, 48 insertions(+)
> >
> > diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.=
h
> > index 66f3933c14f6..ee7aef5f6233 100644
> > --- a/arch/riscv/include/asm/sbi.h
> > +++ b/arch/riscv/include/asm/sbi.h
> > @@ -334,6 +334,11 @@ static inline unsigned long sbi_mk_version(unsigne=
d long major,
> >  }
> >
> >  int sbi_err_map_linux_errno(int err);
> > +
> > +extern bool sbi_debug_console_available;
> > +int sbi_debug_console_write(unsigned int num_bytes, phys_addr_t base_a=
ddr);
> > +int sbi_debug_console_read(unsigned int num_bytes, phys_addr_t base_ad=
dr);
> > +
> >  #else /* CONFIG_RISCV_SBI */
> >  static inline int sbi_remote_fence_i(const struct cpumask *cpu_mask) {=
 return -1; }
> >  static inline void sbi_init(void) {}
> > diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
> > index 5a62ed1da453..73a9c22c3945 100644
> > --- a/arch/riscv/kernel/sbi.c
> > +++ b/arch/riscv/kernel/sbi.c
> > @@ -571,6 +571,44 @@ long sbi_get_mimpid(void)
> >  }
> >  EXPORT_SYMBOL_GPL(sbi_get_mimpid);
> >
> > +bool sbi_debug_console_available;
> > +
> > +int sbi_debug_console_write(unsigned int num_bytes, phys_addr_t base_a=
ddr)
> > +{
> > +     struct sbiret ret;
> > +
> > +     if (!sbi_debug_console_available)
> > +             return -EOPNOTSUPP;
> > +
> > +     if (IS_ENABLED(CONFIG_32BIT))
> > +             ret =3D sbi_ecall(SBI_EXT_DBCN, SBI_EXT_DBCN_CONSOLE_WRIT=
E,
> > +                             num_bytes, lower_32_bits(base_addr),
> > +                             upper_32_bits(base_addr), 0, 0, 0);
> > +     else
> > +             ret =3D sbi_ecall(SBI_EXT_DBCN, SBI_EXT_DBCN_CONSOLE_WRIT=
E,
> > +                             num_bytes, base_addr, 0, 0, 0, 0);
> > +
> > +     return ret.error ? sbi_err_map_linux_errno(ret.error) : ret.value=
;
>
> We can't get perfect mappings, but I wonder if we can do better than
> returning ENOTSUPP for "Failed to write the byte due to I/O errors."
>
> How about
>
>  if (ret.error =3D=3D SBI_ERR_FAILURE)
>      return -EIO;
>
>  return ret.error ? sbi_err_map_linux_errno(ret.error) : ret.value;

Seems overkill but I will update anyway.

>
>
> > +}
> > +
> > +int sbi_debug_console_read(unsigned int num_bytes, phys_addr_t base_ad=
dr)
> > +{
> > +     struct sbiret ret;
> > +
> > +     if (!sbi_debug_console_available)
> > +             return -EOPNOTSUPP;
> > +
> > +     if (IS_ENABLED(CONFIG_32BIT))
> > +             ret =3D sbi_ecall(SBI_EXT_DBCN, SBI_EXT_DBCN_CONSOLE_READ=
,
> > +                             num_bytes, lower_32_bits(base_addr),
> > +                             upper_32_bits(base_addr), 0, 0, 0);
> > +     else
> > +             ret =3D sbi_ecall(SBI_EXT_DBCN, SBI_EXT_DBCN_CONSOLE_READ=
,
> > +                             num_bytes, base_addr, 0, 0, 0, 0);
> > +
> > +     return ret.error ? sbi_err_map_linux_errno(ret.error) : ret.value=
;
>
> Same comment as above.

Okay.

>
> > +}
> > +
> >  void __init sbi_init(void)
> >  {
> >       int ret;
> > @@ -612,6 +650,11 @@ void __init sbi_init(void)
> >                       sbi_srst_reboot_nb.priority =3D 192;
> >                       register_restart_handler(&sbi_srst_reboot_nb);
> >               }
> > +             if ((sbi_spec_version >=3D sbi_mk_version(2, 0)) &&
> > +                 (sbi_probe_extension(SBI_EXT_DBCN) > 0)) {
> > +                     pr_info("SBI DBCN extension detected\n");
> > +                     sbi_debug_console_available =3D true;
> > +             }
> >       } else {
> >               __sbi_set_timer =3D __sbi_set_timer_v01;
> >               __sbi_send_ipi  =3D __sbi_send_ipi_v01;
> > --
> > 2.34.1
> >
>
> Otherwise,
>
> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
>
> Thanks,
> drew

Regards,
Anup