riscv: virt: Use Goldfish RTC device

We extend QEMU RISC-V virt machine by adding Goldfish RTC device
to it. This will allow Guest Linux to sync it's local date/time
with Host date/time via RTC device.
Signed-off-by: NAnup Patel <anup.patel@wdc.com>
Reviewed-by: NPalmer Dabbelt <palmer@sifive.com>
Acked-by: NPalmer Dabbelt <palmer@sifive.com>
Reviewed-by: NAlistair Francis <alistair.francis@wdc.com>
Signed-off-by: NPalmer Dabbelt <palmerdabbelt@google.com>

hw/riscv/Kconfig

@@ -34,6 +34,7 @@ config RISCV_VIRT
     select PCI
     select HART
     select SERIAL
+    select GOLDFISH_RTC
     select VIRTIO_MMIO
     select PCI_EXPRESS_GENERIC_BRIDGE
     select PFLASH_CFI01

hw/riscv/virt.c

@@ -58,6 +58,7 @@ static const struct MemmapEntry {
     [VIRT_DEBUG] =       {        0x0,         0x100 },
     [VIRT_MROM] =        {     0x1000,       0x11000 },
     [VIRT_TEST] =        {   0x100000,        0x1000 },
+    [VIRT_RTC] =         {   0x101000,        0x1000 },
     [VIRT_CLINT] =       {  0x2000000,       0x10000 },
     [VIRT_PLIC] =        {  0xc000000,     0x4000000 },
     [VIRT_UART0] =       { 0x10000000,         0x100 },
@@ -404,6 +405,18 @@ static void create_fdt(RISCVVirtState *s, const struct MemmapEntry *memmap,
     }
     g_free(nodename);
 
+    nodename = g_strdup_printf("/rtc@%lx",
+        (long)memmap[VIRT_RTC].base);
+    qemu_fdt_add_subnode(fdt, nodename);
+    qemu_fdt_setprop_string(fdt, nodename, "compatible",
+        "google,goldfish-rtc");
+    qemu_fdt_setprop_cells(fdt, nodename, "reg",
+        0x0, memmap[VIRT_RTC].base,
+        0x0, memmap[VIRT_RTC].size);
+    qemu_fdt_setprop_cell(fdt, nodename, "interrupt-parent", plic_phandle);
+    qemu_fdt_setprop_cell(fdt, nodename, "interrupts", RTC_IRQ);
+    g_free(nodename);
+
     nodename = g_strdup_printf("/flash@%" PRIx64, flashbase);
     qemu_fdt_add_subnode(s->fdt, nodename);
     qemu_fdt_setprop_string(s->fdt, nodename, "compatible", "cfi-flash");
@@ -601,6 +614,9 @@ static void riscv_virt_board_init(MachineState *machine)
         0, qdev_get_gpio_in(DEVICE(s->plic), UART0_IRQ), 399193,
         serial_hd(0), DEVICE_LITTLE_ENDIAN);
 
+    sysbus_create_simple("goldfish_rtc", memmap[VIRT_RTC].base,
+        qdev_get_gpio_in(DEVICE(s->plic), RTC_IRQ));
+
     virt_flash_create(s);
 
     for (i = 0; i < ARRAY_SIZE(s->flash); i++) {

include/hw/riscv/virt.h

@@ -44,6 +44,7 @@ enum {
     VIRT_DEBUG,
     VIRT_MROM,
     VIRT_TEST,
+    VIRT_RTC,
     VIRT_CLINT,
     VIRT_PLIC,
     VIRT_UART0,
@@ -57,6 +58,7 @@ enum {
 
 enum {
     UART0_IRQ = 10,
+    RTC_IRQ = 11,
     VIRTIO_IRQ = 1, /* 1 to 8 */
     VIRTIO_COUNT = 8,
     PCIE_IRQ = 0x20, /* 32 to 35 */