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diff --git a/include/hw/misc/tz-ppc.h b/include/hw/misc/tz-ppc.h
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+/*
+ * ARM TrustZone peripheral protection controller emulation
+ *
+ * Copyright (c) 2018 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 TrustZone peripheral protection controller (PPC).
+ * It is documented in the ARM CoreLink SIE-200 System IP for Embedded TRM
+ * (DDI 0571G):
+ * https://developer.arm.com/products/architecture/m-profile/docs/ddi0571/g
+ *
+ * The PPC sits in front of peripherals and allows secure software to
+ * configure it to either pass through or reject transactions.
+ * Rejected transactions may be configured to either be aborted, or to
+ * behave as RAZ/WI. An interrupt can be signalled for a rejected transaction.
+ *
+ * The PPC has no register interface -- it is configured purely by a
+ * collection of input signals from other hardware in the system. Typically
+ * they are either hardwired or exposed in an ad-hoc register interface by
+ * the SoC that uses the PPC.
+ *
+ * This QEMU model can be used to model either the AHB5 or APB4 TZ PPC,
+ * since the only difference between them is that the AHB version has a
+ * "default" port which has no security checks applied. In QEMU the default
+ * port can be emulated simply by wiring its downstream devices directly
+ * into the parent address space, since the PPC does not need to intercept
+ * transactions there.
+ *
+ * In the hardware, selection of which downstream port to use is done by
+ * the user's decode logic asserting one of the hsel[] signals. In QEMU,
+ * we provide 16 MMIO regions, one per port, and the user maps these into
+ * the desired addresses to implement the address decode.
+ *
+ * QEMU interface:
+ * + sysbus MMIO regions 0..15: MemoryRegions defining the upstream end
+ *   of each of the 16 ports of the PPC
+ * + Property "port[0..15]": MemoryRegion defining the downstream device(s)
+ *   for each of the 16 ports of the PPC
+ * + Named GPIO inputs "cfg_nonsec[0..15]": set to 1 if the port should be
+ *   accessible to NonSecure transactions
+ * + Named GPIO inputs "cfg_ap[0..15]": set to 1 if the port should be
+ *   accessible to non-privileged transactions
+ * + Named GPIO input "cfg_sec_resp": set to 1 if a rejected transaction should
+ *   result in a transaction error, or 0 for the transaction to RAZ/WI
+ * + Named GPIO input "irq_enable": set to 1 to enable interrupts
+ * + Named GPIO input "irq_clear": set to 1 to clear a pending interrupt
+ * + Named GPIO output "irq": set for a transaction-failed interrupt
+ * + Property "NONSEC_MASK": if a bit is set in this mask then accesses to
+ *   the associated port do not have the TZ security check performed. (This
+ *   corresponds to the hardware allowing this to be set as a Verilog
+ *   parameter.)
+ */
+
+#ifndef TZ_PPC_H
+#define TZ_PPC_H
+
+#include "hw/sysbus.h"
+
+#define TYPE_TZ_PPC "tz-ppc"
+#define TZ_PPC(obj) OBJECT_CHECK(TZPPC, (obj), TYPE_TZ_PPC)
+
+#define TZ_NUM_PORTS 16
+
+typedef struct TZPPC TZPPC;
+
+typedef struct TZPPCPort {
+    TZPPC *ppc;
+    MemoryRegion upstream;
+    AddressSpace downstream_as;
+    MemoryRegion *downstream;
+} TZPPCPort;
+
+struct TZPPC {
+    /*< private >*/
+    SysBusDevice parent_obj;
+
+    /*< public >*/
+
+    /* State: these just track the values of our input signals */
+    bool cfg_nonsec[TZ_NUM_PORTS];
+    bool cfg_ap[TZ_NUM_PORTS];
+    bool cfg_sec_resp;
+    bool irq_enable;
+    bool irq_clear;
+    /* State: are we asserting irq ? */
+    bool irq_status;
+
+    qemu_irq irq;
+
+    /* Properties */
+    uint32_t nonsec_mask;
+
+    TZPPCPort port[TZ_NUM_PORTS];
+};
+
+#endif