Re: [PATCH v4] RISC-V: Use SBI SRST extension when available

[Anup Patel]

On Wed, Mar 10, 2021 at 8:31 AM Palmer Dabbelt <palmer@xxxxxxxxxxx> wrote:
>
> On Mon, 01 Mar 2021 03:58:33 PST (-0800), Anup Patel wrote:
> > The SBI SRST extension provides a standard way to poweroff and
> > reboot the system irrespective to whether Linux RISC-V S-mode
> > is running natively (HS-mode) or inside Guest/VM (VS-mode).
> >
> > The SBI SRST extension is available in latest SBI v0.3-draft
> > specification at: https://github.com/riscv/riscv-sbi-doc.
> >
> > This patch extends Linux RISC-V SBI implementation to detect
> > and use SBI SRST extension.
> >
> > Signed-off-by: Anup Patel <anup.patel@xxxxxxx>
> > ---
> >  arch/riscv/include/asm/sbi.h | 16 ++++++++++++++
> >  arch/riscv/kernel/sbi.c      | 41 +++++++++++++++++++++++++++++++++---
> >  2 files changed, 54 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
> > index 99895d9c3bdd..8add0209c9c7 100644
> > --- a/arch/riscv/include/asm/sbi.h
> > +++ b/arch/riscv/include/asm/sbi.h
> > @@ -27,6 +27,7 @@ enum sbi_ext_id {
> >       SBI_EXT_IPI = 0x735049,
> >       SBI_EXT_RFENCE = 0x52464E43,
> >       SBI_EXT_HSM = 0x48534D,
> > +     SBI_EXT_SRST = 0x53525354,
> >  };
> >
> >  enum sbi_ext_base_fid {
> > @@ -70,6 +71,21 @@ enum sbi_hsm_hart_status {
> >       SBI_HSM_HART_STATUS_STOP_PENDING,
> >  };
> >
> > +enum sbi_ext_srst_fid {
> > +     SBI_EXT_SRST_RESET = 0,
> > +};
> > +
> > +enum sbi_srst_reset_type {
> > +     SBI_SRST_RESET_TYPE_SHUTDOWN = 0,
> > +     SBI_SRST_RESET_TYPE_COLD_REBOOT,
> > +     SBI_SRST_RESET_TYPE_WARM_REBOOT,
> > +};
> > +
> > +enum sbi_srst_reset_reason {
> > +     SBI_SRST_RESET_REASON_NONE = 0,
> > +     SBI_SRST_RESET_REASON_SYS_FAILURE,
> > +};
> > +
> >  #define SBI_SPEC_VERSION_DEFAULT     0x1
> >  #define SBI_SPEC_VERSION_MAJOR_SHIFT 24
> >  #define SBI_SPEC_VERSION_MAJOR_MASK  0x7f
> > diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
> > index f4a7db3d309e..49155588e56c 100644
> > --- a/arch/riscv/kernel/sbi.c
> > +++ b/arch/riscv/kernel/sbi.c
> > @@ -7,6 +7,7 @@
> >
> >  #include <linux/init.h>
> >  #include <linux/pm.h>
> > +#include <linux/reboot.h>
> >  #include <asm/sbi.h>
> >  #include <asm/smp.h>
> >
> > @@ -501,6 +502,32 @@ int sbi_remote_hfence_vvma_asid(const unsigned long *hart_mask,
> >  }
> >  EXPORT_SYMBOL(sbi_remote_hfence_vvma_asid);
> >
> > +static void sbi_srst_reset(unsigned long type, unsigned long reason)
> > +{
> > +     sbi_ecall(SBI_EXT_SRST, SBI_EXT_SRST_RESET, type, reason,
> > +               0, 0, 0, 0);
> > +     pr_warn("%s: type=0x%lx reason=0x%lx failed\n",
> > +             __func__, type, reason);
> > +}
> > +
> > +static int sbi_srst_reboot(struct notifier_block *this,
> > +                        unsigned long mode, void *cmd)
> > +{
> > +     sbi_srst_reset((mode == REBOOT_WARM || mode == REBOOT_SOFT) ?
> > +                    SBI_SRST_RESET_TYPE_WARM_REBOOT :
> > +                    SBI_SRST_RESET_TYPE_COLD_REBOOT,
> > +                    SBI_SRST_RESET_REASON_NONE);
> > +     return NOTIFY_DONE;
> > +}
> > +
> > +static struct notifier_block sbi_srst_reboot_nb;
> > +
> > +static void sbi_srst_power_off(void)
> > +{
> > +     sbi_srst_reset(SBI_SRST_RESET_TYPE_SHUTDOWN,
> > +                    SBI_SRST_RESET_REASON_NONE);
> > +}
> > +
> >  /**
> >   * sbi_probe_extension() - Check if an SBI extension ID is supported or not.
> >   * @extid: The extension ID to be probed.
> > @@ -577,22 +604,30 @@ void __init sbi_init(void)
> >                       sbi_get_firmware_id(), sbi_get_firmware_version());
> >               if (sbi_probe_extension(SBI_EXT_TIME) > 0) {
> >                       __sbi_set_timer = __sbi_set_timer_v02;
> > -                     pr_info("SBI v0.2 TIME extension detected\n");
> > +                     pr_info("SBI TIME extension detected\n");
> >               } else {
> >                       __sbi_set_timer = __sbi_set_timer_v01;
> >               }
> >               if (sbi_probe_extension(SBI_EXT_IPI) > 0) {
> >                       __sbi_send_ipi  = __sbi_send_ipi_v02;
> > -                     pr_info("SBI v0.2 IPI extension detected\n");
> > +                     pr_info("SBI IPI extension detected\n");
>
> These aren't really part of the reset stuff and should be split into a separate
> patch.

Yes, this should be in a separate patch. Thanks for catching.

>
> >               } else {
> >                       __sbi_send_ipi  = __sbi_send_ipi_v01;
> >               }
> >               if (sbi_probe_extension(SBI_EXT_RFENCE) > 0) {
> >                       __sbi_rfence    = __sbi_rfence_v02;
> > -                     pr_info("SBI v0.2 RFENCE extension detected\n");
> > +                     pr_info("SBI RFENCE extension detected\n");
> >               } else {
> >                       __sbi_rfence    = __sbi_rfence_v01;
> >               }
> > +             if (sbi_probe_extension(SBI_EXT_SRST) > 0 &&
> > +                 sbi_minor_version() >= 3) {
> > +                     pr_info("SBI SRST extension detected\n");
> > +                     pm_power_off = sbi_srst_power_off;
> > +                     sbi_srst_reboot_nb.notifier_call = sbi_srst_reboot;
> > +                     sbi_srst_reboot_nb.priority = 192;
> > +                     register_restart_handler(&sbi_srst_reboot_nb);
> > +             }
> >       } else {
> >               __sbi_set_timer = __sbi_set_timer_v01;
> >               __sbi_send_ipi  = __sbi_send_ipi_v01;
>
> This is fine, but I don't want to take things for draft SBI versions until
> they're at least tagged.

Sure, no problem. The SBI v0.3-rc1 release is quite close so hopefully
in next 1-2 months it will be tagged.

Regards,
Anup