[PATCH v3 06/17] acpi: introduce WDAT table for GWDT

[Igor Mammedov <imammedo@redhat.com>]

Add build_gwdt_wdat() to generate a Watchdog Action Table
tailored for the SBSA Generic Watchdog Timer.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
v3:
  (Eric)
    - split '[PATCH v2 11/21] arm: virt: add support for WDAT based watchdog'
      on smaller chunks.
    - add/improve  comments where requested
    - actualy use 'freq' argument passed down by caller
    - simplify magic val on WRR write and add comment
    - group table records by used register
---
 include/hw/acpi/wdat-gwdt.h | 19 +++++++
 hw/acpi/meson.build         |  2 +
 hw/acpi/wdat-gwdt-stub.c    | 16 ++++++
 hw/acpi/wdat-gwdt.c         | 99 +++++++++++++++++++++++++++++++++++++
 4 files changed, 136 insertions(+)
 create mode 100644 include/hw/acpi/wdat-gwdt.h
 create mode 100644 hw/acpi/wdat-gwdt-stub.c
 create mode 100644 hw/acpi/wdat-gwdt.c

diff --git a/include/hw/acpi/wdat-gwdt.h b/include/hw/acpi/wdat-gwdt.h
new file mode 100644
index 0000000000..42339e031e
--- /dev/null
+++ b/include/hw/acpi/wdat-gwdt.h
@@ -0,0 +1,19 @@
+/*
+ * GWDT Watchdog Action Table (WDAT) definition
+ *
+ * Copyright Red Hat, Inc. 2026
+ * Author(s): Igor Mammedov <imammedo@redhat.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#ifndef QEMU_HW_ACPI_WDAT_GWDT_H
+#define QEMU_HW_ACPI_WDAT_GWDT_H
+
+#include "hw/acpi/aml-build.h"
+#include "hw/watchdog/sbsa_gwdt.h"
+
+void build_gwdt_wdat(GArray *table_data, BIOSLinker *linker, const char *oem_id,
+                     const char *oem_table_id, uint64_t rbase, uint64_t cbase,
+                     uint64_t freq);
+
+#endif /* QEMU_HW_ACPI_WDAT_GWDT_H */
diff --git a/hw/acpi/meson.build b/hw/acpi/meson.build
index 0c7bfb278a..09ad488a04 100644
--- a/hw/acpi/meson.build
+++ b/hw/acpi/meson.build
@@ -31,11 +31,13 @@ acpi_ss.add(when: 'CONFIG_ACPI_ERST', if_true: files('erst.c'))
 acpi_ss.add(when: 'CONFIG_IPMI', if_true: files('ipmi.c'))
 stub_ss.add(files('ipmi-stub.c'))
 stub_ss.add(files('acpi-x86-stub.c'))
+acpi_ss.add(when: 'CONFIG_WDT_SBSA', if_true: files('wdat-gwdt.c'))
 if have_tpm
   acpi_ss.add(files('tpm.c'))
 endif
 stub_ss.add(files('acpi-stub.c', 'aml-build-stub.c', 'ghes-stub.c'))
 stub_ss.add(files('pci-bridge-stub.c'))
+stub_ss.add(files('wdat-gwdt-stub.c'))
 system_ss.add_all(when: 'CONFIG_ACPI', if_true: acpi_ss)
 system_ss.add(when: 'CONFIG_GHES_CPER', if_true: files('ghes_cper.c'))
 stub_ss.add(files('ghes_cper_stub.c'))
diff --git a/hw/acpi/wdat-gwdt-stub.c b/hw/acpi/wdat-gwdt-stub.c
new file mode 100644
index 0000000000..4d43783f70
--- /dev/null
+++ b/hw/acpi/wdat-gwdt-stub.c
@@ -0,0 +1,16 @@
+/*
+ * Copyright Red Hat, Inc. 2026
+ * Author(s): Igor Mammedov <imammedo@redhat.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "hw/acpi/wdat-gwdt.h"
+
+void build_gwdt_wdat(GArray *table_data, BIOSLinker *linker, const char *oem_id,
+                     const char *oem_table_id, uint64_t rbase, uint64_t cbase,
+                     uint64_t freq)
+{
+    g_assert_not_reached();
+}
diff --git a/hw/acpi/wdat-gwdt.c b/hw/acpi/wdat-gwdt.c
new file mode 100644
index 0000000000..b30566ef6a
--- /dev/null
+++ b/hw/acpi/wdat-gwdt.c
@@ -0,0 +1,99 @@
+/*
+ * SBSA GWDT Watchdog Action Table (WDAT)
+ *
+ * Copyright Red Hat, Inc. 2026
+ * Author(s): Igor Mammedov <imammedo@redhat.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "hw/acpi/aml-build.h"
+#include "hw/acpi/wdat-gwdt.h"
+#include "hw/acpi/wdat.h"
+#include "hw/watchdog/sbsa_gwdt.h"
+
+#define GWDT_REG(base, reg_offset, reg_width) { \
+                 .space_id = AML_AS_SYSTEM_MEMORY, \
+                 .address = base + reg_offset, .bit_width = reg_width, \
+                 .access_width = AML_DWORD_ACC };
+
+/*
+ *   "Hardware Watchdog Timers Design Specification"
+ *       https://uefi.org/acpi 'Watchdog Action Table (WDAT)'
+ */
+void build_gwdt_wdat(GArray *table_data, BIOSLinker *linker, const char *oem_id,
+                     const char *oem_table_id, uint64_t rbase, uint64_t cbase,
+                     uint64_t freq)
+{
+    AcpiTable table = { .sig = "WDAT", .rev = 1, .oem_id = oem_id,
+                        .oem_table_id = oem_table_id };
+
+    struct AcpiGenericAddress wrr =  GWDT_REG(rbase, 0x0, 32);
+    struct AcpiGenericAddress wor_l =  GWDT_REG(cbase, SBSA_GWDT_WOR, 32);
+    struct AcpiGenericAddress wcs =  GWDT_REG(cbase, SBSA_GWDT_WCS, 32);
+
+    acpi_table_begin(&table, table_data);
+    build_append_int_noprefix(table_data, 0x20, 4); /* Watchdog Header Length */
+    /*
+     * PCI location fields are set to 0xff to indicate
+     * that the watchdog is not a PCI device.
+     */
+    build_append_int_noprefix(table_data, 0xff, 2); /* PCI Segment */
+    build_append_int_noprefix(table_data, 0xff, 1); /* PCI Bus Number */
+    build_append_int_noprefix(table_data, 0xff, 1); /* PCI Device Number */
+    build_append_int_noprefix(table_data, 0xff, 1); /* PCI Function Number */
+    build_append_int_noprefix(table_data, 0, 3);    /* Reserved */
+    /*
+     * WDAT spec: "The clock interval that the WDT uses must be
+     * greater than or equal to 1 millisecond."
+     */
+    g_assert(freq <= 1000);
+    /* Timer Period, ms */
+    build_append_int_noprefix(table_data, 1000 / freq, 4);
+    /*
+     * WDAT spec: "The time-out period before the WDT fires is recommended
+     * to be at least 5 minutes."
+     * Set max count to 10min and min count to 5sec.
+     */
+    build_append_int_noprefix(table_data, 600 * freq, 4); /* Maximum Count */
+    build_append_int_noprefix(table_data, 5 * freq, 4);   /* Minimum Count */
+    /*
+     * WATCHDOG_ENABLED | WATCHDOG_STOPPED_IN_SLEEP_STATE
+     */
+    build_append_int_noprefix(table_data, 0x81, 1); /* Watchdog Flags */
+    build_append_int_noprefix(table_data, 0, 3);    /* Reserved */
+    /*
+     * watchdog instruction entries
+     */
+    build_append_int_noprefix(table_data, 8, 4);
+    /* Action table: WCS (control/status) register actions */
+    build_append_wdat_ins(table_data, WDAT_ACTION_QUERY_RUNNING_STATE,
+        WDAT_INS_READ_VALUE,
+        wcs, 0x1, 0x1);
+    build_append_wdat_ins(table_data, WDAT_ACTION_SET_RUNNING_STATE,
+        WDAT_INS_WRITE_VALUE | WDAT_INS_PRESERVE_REGISTER,
+        wcs, 1, 0x00000001);
+    build_append_wdat_ins(table_data, WDAT_ACTION_QUERY_STOPPED_STATE,
+        WDAT_INS_READ_VALUE,
+        wcs, 0x0, 0x00000001);
+    build_append_wdat_ins(table_data, WDAT_ACTION_SET_STOPPED_STATE,
+        WDAT_INS_WRITE_VALUE | WDAT_INS_PRESERVE_REGISTER,
+        wcs, 0x0, 0x00000001);
+    build_append_wdat_ins(table_data, WDAT_ACTION_QUERY_WATCHDOG_STATUS,
+        WDAT_INS_READ_VALUE,
+        wcs, 0x4, 0x00000004);
+    /* WOR (offset) and WRR (refresh) register actions */
+    build_append_wdat_ins(table_data, WDAT_ACTION_SET_COUNTDOWN_PERIOD,
+        WDAT_INS_WRITE_COUNTDOWN,
+        wor_l, 0, 0xffffffff);
+    /* WRR: any write refreshes the watchdog, value is ignored */
+    build_append_wdat_ins(table_data, WDAT_ACTION_RESET,
+        WDAT_INS_WRITE_VALUE,
+        wrr, 0x1, 0x1);
+    build_append_wdat_ins(table_data, WDAT_ACTION_SET_WATCHDOG_STATUS,
+        WDAT_INS_WRITE_VALUE | WDAT_INS_PRESERVE_REGISTER,
+        wrr, 0x4, 0x4);
+
+    acpi_table_end(linker, &table);
+}
-- 
2.47.3