hw/misc/sse-cpu-pwrctrl: Implement SSE-300 CPU<N>_PWRCTRL register block

The SSE-300 has a new register block CPU<N>_PWRCTRL.  There is one
instance of this per CPU in the system (so just one for the SSE-300),
and as well as the usual CIDR/PIDR ID registers it has just one
register, CPUPWRCFG.  This register allows the guest to configure
behaviour of the system in power-down and deep-sleep states.  Since
QEMU does not model those, we make the register a dummy
reads-as-written implementation.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210219144617.4782-21-peter.maydell@linaro.org

include/hw/misc/armsse-cpu-pwrctrl.h

@@ -0,0 +1,40 @@
+/*
+ * ARM SSE CPU PWRCTRL register block
+ *
+ * Copyright (c) 2021 Linaro Limited
+ * Written by Peter Maydell
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2 or
+ *  (at your option) any later version.
+ */
+
+/*
+ * This is a model of the "CPU<N>_PWRCTRL block" which is part of the
+ * Arm Corstone SSE-300 Example Subsystem and documented in
+ * https://developer.arm.com/documentation/101773/0000
+ *
+ * QEMU interface:
+ *  + sysbus MMIO region 0: the register bank
+ */
+
+#ifndef HW_MISC_ARMSSE_CPU_PWRCTRL_H
+#define HW_MISC_ARMSSE_CPU_PWRCTRL_H
+
+#include "hw/sysbus.h"
+#include "qom/object.h"
+
+#define TYPE_ARMSSE_CPU_PWRCTRL "armsse-cpu-pwrctrl"
+OBJECT_DECLARE_SIMPLE_TYPE(ARMSSECPUPwrCtrl, ARMSSE_CPU_PWRCTRL)
+
+struct ARMSSECPUPwrCtrl {
+    /*< private >*/
+    SysBusDevice parent_obj;
+
+    /*< public >*/
+    MemoryRegion iomem;
+
+    uint32_t cpupwrcfg;
+};
+
+#endif