[PATCH v3 5/5] lib: sbi: Implement System Reset (SRST) SBI extension

[Anup Patel]

The SBI SRST extension has been accepted and merged in the latest
SBI v0.3-draft specification.
(Refer, https://github.com/riscv/riscv-sbi-doc)

It allows to S-mode software to request system shutdown, cold reboot,
and warm reboot.

This patch implements SBI SRST extension as a replacement of the
legacy sbi_shutdown() call of SBI v0.1 specification.

Signed-off-by: Anup Patel <anup.patel at wdc.com>
---
 include/sbi/sbi_ecall.h     |  1 +
 lib/sbi/sbi_ecall.c         |  3 ++
 lib/sbi/sbi_ecall_replace.c | 60 +++++++++++++++++++++++++++++++++++++
 3 files changed, 64 insertions(+)

diff --git a/include/sbi/sbi_ecall.h b/include/sbi/sbi_ecall.h
index 3273ba6..1ef86e2 100644
--- a/include/sbi/sbi_ecall.h
+++ b/include/sbi/sbi_ecall.h
@@ -37,6 +37,7 @@ extern struct sbi_ecall_extension ecall_rfence;
 extern struct sbi_ecall_extension ecall_ipi;
 extern struct sbi_ecall_extension ecall_vendor;
 extern struct sbi_ecall_extension ecall_hsm;
+extern struct sbi_ecall_extension ecall_srst;
 
 u16 sbi_ecall_version_major(void);
 
diff --git a/lib/sbi/sbi_ecall.c b/lib/sbi/sbi_ecall.c
index 64c9933..6d41cff 100644
--- a/lib/sbi/sbi_ecall.c
+++ b/lib/sbi/sbi_ecall.c
@@ -167,6 +167,9 @@ int sbi_ecall_init(void)
 	if (ret)
 		return ret;
 	ret = sbi_ecall_register_extension(&ecall_hsm);
+	if (ret)
+		return ret;
+	ret = sbi_ecall_register_extension(&ecall_srst);
 	if (ret)
 		return ret;
 	ret = sbi_ecall_register_extension(&ecall_legacy);
diff --git a/lib/sbi/sbi_ecall_replace.c b/lib/sbi/sbi_ecall_replace.c
index e460c30..d06dfa2 100644
--- a/lib/sbi/sbi_ecall_replace.c
+++ b/lib/sbi/sbi_ecall_replace.c
@@ -14,6 +14,7 @@
 #include <sbi/sbi_error.h>
 #include <sbi/sbi_hart.h>
 #include <sbi/sbi_ipi.h>
+#include <sbi/sbi_system.h>
 #include <sbi/sbi_timer.h>
 #include <sbi/sbi_tlb.h>
 
@@ -127,3 +128,62 @@ struct sbi_ecall_extension ecall_ipi = {
 	.extid_end = SBI_EXT_IPI,
 	.handle = sbi_ecall_ipi_handler,
 };
+
+static int sbi_ecall_srst_handler(unsigned long extid, unsigned long funcid,
+				  unsigned long *args, unsigned long *out_val,
+				  struct sbi_trap_info *out_trap)
+{
+	if (funcid == SBI_EXT_SRST_RESET) {
+		if ((((u32)-1U) <= ((u64)args[0])) ||
+		    (((u32)-1U) <= ((u64)args[1])))
+			return SBI_EINVAL;
+
+		switch (args[0]) {
+		case SBI_SRST_RESET_TYPE_SHUTDOWN:
+		case SBI_SRST_RESET_TYPE_COLD_REBOOT:
+		case SBI_SRST_RESET_TYPE_WARM_REBOOT:
+			break;
+		default:
+			return SBI_ENOTSUPP;
+		}
+
+		switch (args[1]) {
+		case SBI_SRST_RESET_REASON_NONE:
+		case SBI_SRST_RESET_REASON_SYSFAIL:
+			break;
+		default:
+			return SBI_ENOTSUPP;
+		}
+
+		if (sbi_system_reset_supported(args[0], args[1]))
+			sbi_system_reset(args[0], args[1]);
+	}
+
+	return SBI_ENOTSUPP;
+}
+
+static int sbi_ecall_srst_probe(unsigned long extid, unsigned long *out_val)
+{
+	u32 type, count = 0;
+
+	/*
+	 * At least one standard reset types should be supported by
+	 * the platform for SBI SRST extension to be usable.
+	 */
+
+	for (type = 0; type <= SBI_SRST_RESET_TYPE_LAST; type++) {
+		if (sbi_system_reset_supported(type,
+					SBI_SRST_RESET_REASON_NONE))
+			count++;
+	}
+
+	*out_val = (count) ? 1 : 0;
+	return 0;
+}
+
+struct sbi_ecall_extension ecall_srst = {
+	.extid_start = SBI_EXT_SRST,
+	.extid_end = SBI_EXT_SRST,
+	.handle = sbi_ecall_srst_handler,
+	.probe = sbi_ecall_srst_probe,
+};
-- 
2.25.1