[PATCH v8 08/11] RISC-V: Add SBI HSM extension

[Atish Patra <atish.patra@wdc.com>]

SBI specification defines HSM extension that allows to start/stop a hart
by a supervisor anytime. The specification is available at

https://github.com/riscv/riscv-sbi-doc/blob/master/riscv-sbi.adoc

Implement SBI HSM extension.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
---
 arch/riscv/include/asm/sbi.h    | 15 +++++++++++
 arch/riscv/kernel/Makefile      |  3 +++
 arch/riscv/kernel/cpu_ops_sbi.c | 48 +++++++++++++++++++++++++++++++++
 arch/riscv/kernel/sbi.c         |  3 ++-
 4 files changed, 68 insertions(+), 1 deletion(-)
 create mode 100644 arch/riscv/kernel/cpu_ops_sbi.c

diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
index d55d8090ab5c..0981a0c97eda 100644
--- a/arch/riscv/include/asm/sbi.h
+++ b/arch/riscv/include/asm/sbi.h
@@ -26,6 +26,7 @@ enum sbi_ext_id {
 	SBI_EXT_TIME = 0x54494D45,
 	SBI_EXT_IPI = 0x735049,
 	SBI_EXT_RFENCE = 0x52464E43,
+	SBI_EXT_HSM = 0x48534D,
 };
 
 enum sbi_ext_base_fid {
@@ -56,6 +57,19 @@ enum sbi_ext_rfence_fid {
 	SBI_EXT_RFENCE_REMOTE_HFENCE_VVMA_ASID,
 };
 
+enum sbi_ext_hsm_fid {
+	SBI_EXT_HSM_HART_START = 0,
+	SBI_EXT_HSM_HART_STOP,
+	SBI_EXT_HSM_HART_STATUS,
+};
+
+enum sbi_hsm_hart_status {
+	SBI_HSM_HART_STATUS_AVAILABLE = 0,
+	SBI_HSM_HART_STATUS_NOT_AVAILABLE,
+	SBI_HSM_HART_STATUS_START_PENDING,
+	SBI_HSM_HART_STATUS_STOP_PENDING,
+};
+
 #define SBI_SPEC_VERSION_DEFAULT	0x1
 #define SBI_SPEC_VERSION_MAJOR_SHIFT	24
 #define SBI_SPEC_VERSION_MAJOR_MASK	0x7f
@@ -130,6 +144,7 @@ static inline unsigned long sbi_minor_version(void)
 {
 	return sbi_spec_version & SBI_SPEC_VERSION_MINOR_MASK;
 }
+int sbi_err_map_linux_errno(int err);
 #else /* CONFIG_RISCV_SBI */
 /* stubs for code that is only reachable under IS_ENABLED(CONFIG_RISCV_SBI): */
 void sbi_set_timer(uint64_t stime_value);
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index f81a6ff88005..a0be34b96846 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -44,5 +44,8 @@ obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o
 obj-$(CONFIG_PERF_EVENTS)	+= perf_callchain.o
 obj-$(CONFIG_HAVE_PERF_REGS)	+= perf_regs.o
 obj-$(CONFIG_RISCV_SBI)		+= sbi.o
+ifeq ($(CONFIG_RISCV_SBI), y)
+obj-$(CONFIG_SMP) += cpu_ops_sbi.o
+endif
 
 clean:
diff --git a/arch/riscv/kernel/cpu_ops_sbi.c b/arch/riscv/kernel/cpu_ops_sbi.c
new file mode 100644
index 000000000000..9bdb60e0a4df
--- /dev/null
+++ b/arch/riscv/kernel/cpu_ops_sbi.c
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * HSM extension and cpu_ops implementation.
+ *
+ * Copyright (c) 2020 Western Digital Corporation or its affiliates.
+ */
+
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <asm/sbi.h>
+#include <asm/smp.h>
+
+static int sbi_hsm_hart_stop(void)
+{
+	struct sbiret ret;
+
+	ret = sbi_ecall(SBI_EXT_HSM, SBI_EXT_HSM_HART_STOP, 0, 0, 0, 0, 0, 0);
+
+	if (ret.error)
+		return sbi_err_map_linux_errno(ret.error);
+	else
+		return 0;
+}
+
+static int sbi_hsm_hart_start(unsigned long hartid, unsigned long saddr,
+		       unsigned long priv)
+{
+	struct sbiret ret;
+
+	ret = sbi_ecall(SBI_EXT_HSM, SBI_EXT_HSM_HART_START,
+			      hartid, saddr, priv, 0, 0, 0);
+	if (ret.error)
+		return sbi_err_map_linux_errno(ret.error);
+	else
+		return 0;
+}
+
+static int sbi_hsm_hart_get_status(unsigned long hartid)
+{
+	struct sbiret ret;
+
+	ret = sbi_ecall(SBI_EXT_HSM, SBI_EXT_HSM_HART_STATUS,
+			      hartid, 0, 0, 0, 0, 0);
+	if (ret.error)
+		return sbi_err_map_linux_errno(ret.error);
+	else
+		return ret.value;
+}
diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
index cd0f68aeac70..45ad49269f2c 100644
--- a/arch/riscv/kernel/sbi.c
+++ b/arch/riscv/kernel/sbi.c
@@ -47,7 +47,7 @@ struct sbiret sbi_ecall(int ext, int fid, unsigned long arg0,
 }
 EXPORT_SYMBOL(sbi_ecall);
 
-static int sbi_err_map_linux_errno(int err)
+int sbi_err_map_linux_errno(int err)
 {
 	switch (err) {
 	case SBI_SUCCESS:
@@ -64,6 +64,7 @@ static int sbi_err_map_linux_errno(int err)
 		return -ENOTSUPP;
 	};
 }
+EXPORT_SYMBOL(sbi_err_map_linux_errno);
 
 #ifdef CONFIG_RISCV_SBI_V01
 /**
-- 
2.24.0