docs: Add documentation for shakti_c machine

Add documentation for Shakti C reference platform.

Signed-off-by: Vijai Kumar K <vijai@behindbytes.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20210412174248.8668-1-vijai@behindbytes.com
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
[ Changes from Bin Meng:
 - Add missing TOC
 Message-id: 20210430070534.1487242-1-bmeng.cn@gmail.com
]
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

docs/system/riscv/shakti-c.rst

@@ -0,0 +1,82 @@
+Shakti C Reference Platform (``shakti_c``)
+==========================================
+
+Shakti C Reference Platform is a reference platform based on arty a7 100t
+for the Shakti SoC.
+
+Shakti SoC is a SoC based on the Shakti C-class processor core. Shakti C
+is a 64bit RV64GCSUN processor core.
+
+For more details on Shakti SoC, please see:
+https://gitlab.com/shaktiproject/cores/shakti-soc/-/blob/master/fpga/boards/artya7-100t/c-class/README.rst
+
+For more info on the Shakti C-class core, please see:
+https://c-class.readthedocs.io/en/latest/
+
+Supported devices
+-----------------
+
+The ``shakti_c`` machine supports the following devices:
+
+ * 1 C-class core
+ * Core Level Interruptor (CLINT)
+ * Platform-Level Interrupt Controller (PLIC)
+ * 1 UART
+
+Boot options
+------------
+
+The ``shakti_c`` machine can start using the standard -bios
+functionality for loading the baremetal application or opensbi.
+
+Boot the machine
+----------------
+
+Shakti SDK
+~~~~~~~~~~
+Shakti SDK can be used to generate the baremetal example UART applications.
+
+.. code-block:: bash
+
+   $ git clone https://gitlab.com/behindbytes/shakti-sdk.git
+   $ cd shakti-sdk
+   $ make software PROGRAM=loopback TARGET=artix7_100t
+
+Binary would be generated in:
+  software/examples/uart_applns/loopback/output/loopback.shakti
+
+You could also download the precompiled example applicatons using below
+commands.
+
+.. code-block:: bash
+
+   $ wget -c https://gitlab.com/behindbytes/shakti-binaries/-/raw/master/sdk/shakti_sdk_qemu.zip
+   $ unzip shakti_sdk_qemu.zip
+
+Then we can run the UART example using:
+
+.. code-block:: bash
+
+   $ qemu-system-riscv64 -M shakti_c -nographic \
+      -bios path/to/shakti_sdk_qemu/loopback.shakti
+
+OpenSBI
+~~~~~~~
+We can also run OpenSBI with Test Payload.
+
+.. code-block:: bash
+
+   $ git clone https://github.com/riscv/opensbi.git -b v0.9
+   $ cd opensbi
+   $ wget -c https://gitlab.com/behindbytes/shakti-binaries/-/raw/master/dts/shakti.dtb
+   $ export CROSS_COMPILE=riscv64-unknown-elf-
+   $ export FW_FDT_PATH=./shakti.dtb
+   $ make PLATFORM=generic
+
+fw_payload.elf would be generated in build/platform/generic/firmware/fw_payload.elf.
+Boot it using the below qemu command.
+
+.. code-block:: bash
+
+   $ qemu-system-riscv64 -M shakti_c -nographic \
+      -bios path/to/fw_payload.elf

docs/system/target-riscv.rst

@@ -67,6 +67,7 @@ undocumented; you can get a complete list by running
    :maxdepth: 1
 
    riscv/microchip-icicle-kit
+   riscv/shakti-c
    riscv/sifive_u
 
 RISC-V CPU features