riscv: Add initial support for Shakti C machine

Add support for emulating Shakti reference platform based on C-class
running on arty-100T board.

https://gitlab.com/shaktiproject/cores/shakti-soc/-/blob/master/README.rst

Signed-off-by: Vijai Kumar K <vijai@behindbytes.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20210401181457.73039-3-vijai@behindbytes.com
[Changes by AF:
 - Check for mstate->firmware before loading it
]
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

include/hw/riscv/shakti_c.h

@@ -0,0 +1,73 @@
+/*
+ * Shakti C-class SoC emulation
+ *
+ * Copyright (c) 2021 Vijai Kumar K <vijai@behindbytes.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2 or later, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef HW_SHAKTI_H
+#define HW_SHAKTI_H
+
+#include "hw/riscv/riscv_hart.h"
+#include "hw/boards.h"
+
+#define TYPE_RISCV_SHAKTI_SOC "riscv.shakti.cclass.soc"
+#define RISCV_SHAKTI_SOC(obj) \
+    OBJECT_CHECK(ShaktiCSoCState, (obj), TYPE_RISCV_SHAKTI_SOC)
+
+typedef struct ShaktiCSoCState {
+    /*< private >*/
+    DeviceState parent_obj;
+
+    /*< public >*/
+    RISCVHartArrayState cpus;
+    DeviceState *plic;
+    MemoryRegion rom;
+
+} ShaktiCSoCState;
+
+#define TYPE_RISCV_SHAKTI_MACHINE MACHINE_TYPE_NAME("shakti_c")
+#define RISCV_SHAKTI_MACHINE(obj) \
+    OBJECT_CHECK(ShaktiCMachineState, (obj), TYPE_RISCV_SHAKTI_MACHINE)
+typedef struct ShaktiCMachineState {
+    /*< private >*/
+    MachineState parent_obj;
+
+    /*< public >*/
+    ShaktiCSoCState soc;
+} ShaktiCMachineState;
+
+enum {
+    SHAKTI_C_ROM,
+    SHAKTI_C_RAM,
+    SHAKTI_C_UART,
+    SHAKTI_C_GPIO,
+    SHAKTI_C_PLIC,
+    SHAKTI_C_CLINT,
+    SHAKTI_C_I2C,
+};
+
+#define SHAKTI_C_PLIC_HART_CONFIG "MS"
+/* Including Interrupt ID 0 (no interrupt)*/
+#define SHAKTI_C_PLIC_NUM_SOURCES 28
+/* Excluding Priority 0 */
+#define SHAKTI_C_PLIC_NUM_PRIORITIES 2
+#define SHAKTI_C_PLIC_PRIORITY_BASE 0x04
+#define SHAKTI_C_PLIC_PENDING_BASE 0x1000
+#define SHAKTI_C_PLIC_ENABLE_BASE 0x2000
+#define SHAKTI_C_PLIC_ENABLE_STRIDE 0x80
+#define SHAKTI_C_PLIC_CONTEXT_BASE 0x200000
+#define SHAKTI_C_PLIC_CONTEXT_STRIDE 0x1000
+
+#endif