ACK: [linux-riscv][J][PATCH] RISC-V: Use SBI SRST extension when available

[Tim Gardner]

Acked-by: Tim Gardner <tim.gardner at canonical.com>

On 2/25/22 13:26, Dimitri John Ledkov wrote:
> From: Anup Patel <anup.patel at wdc.com>
> 
> 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)
> 
> 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>
> Signed-off-by: Palmer Dabbelt <palmer at rivosinc.com>
> (cherry picked from commit b579dfe71a6a5c3967ca9ad648673b6ca10ab0d5)
> Bug-Link: https://bugs.launchpad.net/bugs/1955042
> Signed-off-by: Dimitri John Ledkov <dimitri.ledkov at canonical.com>
> ---
> 
>   Test built and booted on unmatched board, and observed that poweroff
>   is supported and works correctly via SBI SRST instead of
>   gpio-poweroff. This is preffered, as in the future SBI SRST will the
>   more universal way to poweroff and reboot.
> 
>   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 0d42693cb6..289621da4a 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 7402a417f3..9a84f0cb51 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;

-- 
-----------
Tim Gardner
Canonical, Inc