[PATCH v7 1/1] RISC-V: Use SBI SRST extension when available

[Palmer Dabbelt]

On Mon, 21 Jun 2021 21:46:46 PDT (-0700), anup at brainfault.org wrote:
> Hi Palmer,
>
> On Wed, Jun 9, 2021 at 5:43 PM Anup Patel <anup.patel at wdc.com> 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 the SBI v0.3 specification.
>> (Refer, https://github.com/riscv/riscv-sbi-doc/releases/tag/v0.3.0-rc1)
>
> Can you please consider this patch for Linux-5.14-rc1 ?
>
> The SBI v0.3 spec is already frozen and this patch has been
> floating on LKML for quite a few months now.

I didn't realize that SBI-0.3 had been frozed.  That link is to a RC, 
the cooresponding v0.3.0 tag isn't in that repo.  Can you give me a 
pointer to the frozen spec?

>
> Regards,
> Anup
>
>>
>> This patch extends Linux RISC-V SBI implementation to detect
>> and use SBI SRST extension.
>>
>> Signed-off-by: Anup Patel <anup.patel at wdc.com>
>> Reviewed-by: Atish Patra <atish.patra at wdc.com>
>> ---
>>  arch/riscv/include/asm/sbi.h | 24 ++++++++++++++++++++++++
>>  arch/riscv/kernel/sbi.c      | 35 +++++++++++++++++++++++++++++++++++
>>  2 files changed, 59 insertions(+)
>>
>> diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
>> index 0d42693cb65e..289621da4a2a 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
>> @@ -148,6 +164,14 @@ static inline unsigned long sbi_minor_version(void)
>>         return sbi_spec_version & SBI_SPEC_VERSION_MINOR_MASK;
>>  }
>>
>> +/* Make SBI version */
>> +static inline unsigned long sbi_mk_version(unsigned long major,
>> +                                           unsigned long minor)
>> +{
>> +       return ((major & SBI_SPEC_VERSION_MAJOR_MASK) <<
>> +               SBI_SPEC_VERSION_MAJOR_SHIFT) | minor;
>> +}
>> +
>>  int sbi_err_map_linux_errno(int err);
>>  #else /* CONFIG_RISCV_SBI */
>>  static inline int sbi_remote_fence_i(const unsigned long *hart_mask) { return -1; }
>> diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
>> index 7402a417f38e..9a84f0cb5175 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.
>> @@ -608,6 +635,14 @@ void __init sbi_init(void)
>>                 } else {
>>                         __sbi_rfence    = __sbi_rfence_v01;
>>                 }
>> +               if ((sbi_spec_version >= sbi_mk_version(0, 3)) &&
>> +                   (sbi_probe_extension(SBI_EXT_SRST) > 0)) {
>> +                       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;
>> --
>> 2.25.1
>>