RISC-V SBI 概述

// opensbi/lib/sbi/sbi_trap.c: 303

case CAUSE_SUPERVISOR_ECALL:
case CAUSE_MACHINE_ECALL:
	rc  = sbi_ecall_handler(regs);
	msg = "ecall handler failed";
	break;

// opensbi/lib/sbi/sbi_ecall.c: 108

	ext = sbi_ecall_find_extension(extension_id);
	if (ext && ext->handle) {
		ret = ext->handle(extension_id, func_id,
				  regs, &out_val, &trap);
		if (extension_id >= SBI_EXT_0_1_SET_TIMER &&
		    extension_id <= SBI_EXT_0_1_SHUTDOWN)
			is_0_1_spec = 1;
	} else {
		ret = SBI_ENOTSUPP;
	}

// opensbi/lib/sbi/sbi_init.c: 264

    rc = sbi_xxx_init(scratch, true);
	if (rc) {
		sbi_printf("%s: xxx init failed (error %d)\n",
			   __func__, rc);
		sbi_hart_hang();
	}

// opensbi/lib/sbi/sbi_ecall_base.c: 56

case SBI_EXT_BASE_GET_MVENDORID:
	*out_val = csr_read(CSR_MVENDORID);
	break;

// opensbi/include/sbi/sbi_ecall_interface.h: 15

/* SBI Extension IDs */
#define SBI_EXT_0_1_SET_TIMER			0x0
#define SBI_EXT_0_1_CONSOLE_PUTCHAR		0x1
#define SBI_EXT_0_1_CONSOLE_GETCHAR		0x2
#define SBI_EXT_0_1_CLEAR_IPI			0x3
#define SBI_EXT_0_1_SEND_IPI			0x4
#define SBI_EXT_0_1_REMOTE_FENCE_I		0x5
#define SBI_EXT_0_1_REMOTE_SFENCE_VMA		0x6
#define SBI_EXT_0_1_REMOTE_SFENCE_VMA_ASID	0x7
#define SBI_EXT_0_1_SHUTDOWN			0x8
#define SBI_EXT_BASE				0x10
#define SBI_EXT_TIME				0x54494D45
#define SBI_EXT_IPI				0x735049
#define SBI_EXT_RFENCE				0x52464E43
#define SBI_EXT_HSM				0x48534D
#define SBI_EXT_SRST				0x53525354
#define SBI_EXT_PMU				0x504D55
#define SBI_EXT_DBCN				0x4442434E
#define SBI_EXT_SUSP				0x53555350
#define SBI_EXT_CPPC				0x43505043

/* SBI function IDs for BASE extension */
#define SBI_EXT_BASE_GET_SPEC_VERSION		0x0
#define SBI_EXT_BASE_GET_IMP_ID			0x1
#define SBI_EXT_BASE_GET_IMP_VERSION		0x2
#define SBI_EXT_BASE_PROBE_EXT			0x3
#define SBI_EXT_BASE_GET_MVENDORID		0x4
#define SBI_EXT_BASE_GET_MARCHID		0x5
#define SBI_EXT_BASE_GET_MIMPID			0x6

/* SBI function IDs for TIME extension */
#define SBI_EXT_TIME_SET_TIMER			0x0

/* SBI function IDs for IPI extension */
#define SBI_EXT_IPI_SEND_IPI			0x0

/* SBI function IDs for RFENCE extension */
#define SBI_EXT_RFENCE_REMOTE_FENCE_I		0x0
#define SBI_EXT_RFENCE_REMOTE_SFENCE_VMA	0x1
#define SBI_EXT_RFENCE_REMOTE_SFENCE_VMA_ASID	0x2
#define SBI_EXT_RFENCE_REMOTE_HFENCE_GVMA_VMID	0x3
#define SBI_EXT_RFENCE_REMOTE_HFENCE_GVMA	0x4
#define SBI_EXT_RFENCE_REMOTE_HFENCE_VVMA_ASID	0x5
#define SBI_EXT_RFENCE_REMOTE_HFENCE_VVMA	0x6

/* SBI function IDs for HSM extension */
#define SBI_EXT_HSM_HART_START			0x0
#define SBI_EXT_HSM_HART_STOP			0x1
#define SBI_EXT_HSM_HART_GET_STATUS		0x2
#define SBI_EXT_HSM_HART_SUSPEND		0x3

#define SBI_HSM_STATE_STARTED			0x0
#define SBI_HSM_STATE_STOPPED			0x1
#define SBI_HSM_STATE_START_PENDING		0x2
#define SBI_HSM_STATE_STOP_PENDING		0x3
#define SBI_HSM_STATE_SUSPENDED			0x4
#define SBI_HSM_STATE_SUSPEND_PENDING		0x5
#define SBI_HSM_STATE_RESUME_PENDING		0x6

#define SBI_HSM_SUSP_BASE_MASK			0x7fffffff
#define SBI_HSM_SUSP_NON_RET_BIT		0x80000000
#define SBI_HSM_SUSP_PLAT_BASE			0x10000000

#define SBI_HSM_SUSPEND_RET_DEFAULT		0x00000000
#define SBI_HSM_SUSPEND_RET_PLATFORM		SBI_HSM_SUSP_PLAT_BASE
#define SBI_HSM_SUSPEND_RET_LAST		SBI_HSM_SUSP_BASE_MASK
#define SBI_HSM_SUSPEND_NON_RET_DEFAULT		SBI_HSM_SUSP_NON_RET_BIT
#define SBI_HSM_SUSPEND_NON_RET_PLATFORM	(SBI_HSM_SUSP_NON_RET_BIT | \
						 SBI_HSM_SUSP_PLAT_BASE)
#define SBI_HSM_SUSPEND_NON_RET_LAST		(SBI_HSM_SUSP_NON_RET_BIT | \
						 SBI_HSM_SUSP_BASE_MASK)

/* SBI function IDs for SRST extension */
#define SBI_EXT_SRST_RESET			0x0

#define SBI_SRST_RESET_TYPE_SHUTDOWN		0x0
#define SBI_SRST_RESET_TYPE_COLD_REBOOT	0x1
#define SBI_SRST_RESET_TYPE_WARM_REBOOT	0x2
#define SBI_SRST_RESET_TYPE_LAST	SBI_SRST_RESET_TYPE_WARM_REBOOT

#define SBI_SRST_RESET_REASON_NONE	0x0
#define SBI_SRST_RESET_REASON_SYSFAIL	0x1

/* SBI function IDs for PMU extension */
#define SBI_EXT_PMU_NUM_COUNTERS	0x0
#define SBI_EXT_PMU_COUNTER_GET_INFO	0x1
#define SBI_EXT_PMU_COUNTER_CFG_MATCH	0x2
#define SBI_EXT_PMU_COUNTER_START	0x3
#define SBI_EXT_PMU_COUNTER_STOP	0x4
#define SBI_EXT_PMU_COUNTER_FW_READ	0x5
#define SBI_EXT_PMU_COUNTER_FW_READ_HI	0x6

// linux/arch/riscv/kernel/sbi.c: 25

struct sbiret sbi_ecall(int ext, int fid, unsigned long arg0,
			unsigned long arg1, unsigned long arg2,
			unsigned long arg3, unsigned long arg4,
			unsigned long arg5)
{
	struct sbiret ret;

	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);
	register uintptr_t a3 asm ("a3") = (uintptr_t)(arg3);
	register uintptr_t a4 asm ("a4") = (uintptr_t)(arg4);
	register uintptr_t a5 asm ("a5") = (uintptr_t)(arg5);
	register uintptr_t a6 asm ("a6") = (uintptr_t)(fid);
	register uintptr_t a7 asm ("a7") = (uintptr_t)(ext);
	asm volatile ("ecall"
		      : "+r" (a0), "+r" (a1)
		      : "r" (a2), "r" (a3), "r" (a4), "r" (a5), "r" (a6), "r" (a7)
		      : "memory");
	ret.error = a0;
	ret.value = a1;

	return ret;
}

// linux/arch/riscv/kernel/sbi.c: 101

void sbi_console_putchar(int ch)
{
	sbi_ecall(SBI_EXT_0_1_CONSOLE_PUTCHAR, 0, ch, 0, 0, 0, 0, 0);
}

// linux/arch/riscv/include/asm/sbi.h: 14

enum sbi_ext_id {
#ifdef CONFIG_RISCV_SBI_V01
	SBI_EXT_0_1_SET_TIMER = 0x0,
	SBI_EXT_0_1_CONSOLE_PUTCHAR = 0x1,
	SBI_EXT_0_1_CONSOLE_GETCHAR = 0x2,
	SBI_EXT_0_1_CLEAR_IPI = 0x3,
	SBI_EXT_0_1_SEND_IPI = 0x4,
	SBI_EXT_0_1_REMOTE_FENCE_I = 0x5,
	SBI_EXT_0_1_REMOTE_SFENCE_VMA = 0x6,
	SBI_EXT_0_1_REMOTE_SFENCE_VMA_ASID = 0x7,
	SBI_EXT_0_1_SHUTDOWN = 0x8,
#endif
	SBI_EXT_BASE = 0x10,
	SBI_EXT_TIME = 0x54494D45,
	SBI_EXT_IPI = 0x735049,
	SBI_EXT_RFENCE = 0x52464E43,
	SBI_EXT_HSM = 0x48534D,
	SBI_EXT_SRST = 0x53525354,
	SBI_EXT_PMU = 0x504D55,

	/* Experimentals extensions must lie within this range */
	SBI_EXT_EXPERIMENTAL_START = 0x08000000,
	SBI_EXT_EXPERIMENTAL_END = 0x08FFFFFF,

	/* Vendor extensions must lie within this range */
	SBI_EXT_VENDOR_START = 0x09000000,
	SBI_EXT_VENDOR_END = 0x09FFFFFF,
};

// linux/arch/riscv/kernel/sbi.c: 101

#ifdef CONFIG_RISCV_SBI_V01

// 如果支持 SBI 0.1，下面的函数可以被调用
...
void sbi_console_putchar(int ch)
{
	sbi_ecall(SBI_EXT_0_1_CONSOLE_PUTCHAR, 0, ch, 0, 0, 0, 0, 0);
}
...
...
#else

// 如果 SBI 0.1 不被支持，返回 remote fence extension is not available in SBI x.x
...
static void __sbi_set_timer_v01(uint64_t stime_value)
{
	pr_warn("Timer extension is not available in SBI v%lu.%lu\n",
		sbi_major_version(), sbi_minor_version());
}
...
...
#endif /* CONFIG_RISCV_SBI_V01 */

// linux/arch/riscv/kernel/sbi.c: 222

static void __sbi_set_timer_v02(uint64_t stime_value)
{
#if __riscv_xlen == 32
	sbi_ecall(SBI_EXT_TIME, SBI_EXT_TIME_SET_TIMER, stime_value,
		  stime_value >> 32, 0, 0, 0, 0);
#else
	sbi_ecall(SBI_EXT_TIME, SBI_EXT_TIME_SET_TIMER, stime_value, 0,
		  0, 0, 0, 0);
#endif
}