This patch adds SBI v0.2 compliant system reboot extension. It defines
the sbi_system_reboot function which does different things based on
reboot_type parameter:
1. shutdown    - Power-off the entire system
2. cold reboot - Power-cycle the entire system
3. warm reboot - Power-cycle only parts of system based on SOC vendor
                 design choices

The sbi_system_reboot function defined here is also an replacement of
SBI v0.1 shutdown function.

Signed-off-by: Atish Patra <atish.patra@...>
Signed-off-by: Anup Patel <anup.patel@...>
---
 riscv-sbi.adoc | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/riscv-sbi.adoc b/riscv-sbi.adoc
index 8137686..d93a5c2 100644
--- a/riscv-sbi.adoc
+++ b/riscv-sbi.adoc
@@ -615,6 +615,53 @@ state of the hart at the time of return value verification.
 | sbi_hart_get_status          |           2 |     0x48534D
 |===

+== System Reboot Extension, Extension ID: 0x53524254 (SRBT)
+
+The System Reboot Extension provides a set of functions that allow the
+supervisor software to request system-level reboot or shutdown.
+
+[source, C]
+----
+struct sbiret sbi_system_reboot(unsigned long reboot_type)
+----
+
+Reboot the system based on provided reboot type. This is a synchronous call
+and does not return if it succeeds.
+
+The reboot_type parameter is 32 bit wide and has following possible values:
+
+[cols="<,>",options="header,compact"]
+|===
+| Value                        | Description
+| 0x00000000                   | Shutdown
+| 0x00000001                   | Cold reboot
+| 0x00000002                   | Warm reboot
+| 0x00000003 - 0xEFFFFFFF      | Reserved for future use
+| 0xF0000000 - 0xFFFFFFFF      | Vendor or platform specific reboot type
+| 0x100000000 - 2^XELN-1       | Reserved and unusable on RV32
+|===
+
+Cold reboot results in complete power cycle of the entire system while
+warm reboot depends on SOC vendor design choices.
+
+*Returns* one of the following possible SBI error codes through sbiret.error
+upon failure.
+
+[cols="<,>",options="header,compact"]
+|===
+| Error code                | Description
+| SBI_ERR_INVALID_PARAM     | `reboot_type` is not valid.
+| SBI_ERR_FAILED            | Reboot request failed for unknown reasons.
+|===
+
+=== SRBT Function Listing
+
+[cols="<,,>",options="header,compact"]
+|===
+| Function Name                 | Function ID | Extension ID
+| sbi_system_reboot                    |           0 |   0x53524254
+|===
+
 == Experimental SBI Extension Space, Extension IDs 0x0800000 through 0x08FFFFFF

 No management.
--
2.17.1