[PATCH v4 1/2] hw/riscv: Add fw_cfg support to virt

[Asherah Connor <ashe@kivikakk.ee>]

Provides fw_cfg for the virt machine on riscv.  This enables
using e.g.  ramfb later.

Signed-off-by: Asherah Connor <ashe@kivikakk.ee>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
---

Changes in v4:
* Adapt for changes made in c65d7080d8 "hw/riscv: migrate fdt field to
  generic MachineState".

Changes in v3:
* Document why fw_cfg is done when it is.
* Move VIRT_FW_CFG before VIRT_FLASH.

Changes in v2:
* Add DMA support (needed for writes).

 hw/riscv/Kconfig        |  1 +
 hw/riscv/virt.c         | 30 ++++++++++++++++++++++++++++++
 include/hw/riscv/virt.h |  2 ++
 3 files changed, 33 insertions(+)

diff --git a/hw/riscv/Kconfig b/hw/riscv/Kconfig
index d139074b02..1de18cdcf1 100644
--- a/hw/riscv/Kconfig
+++ b/hw/riscv/Kconfig
@@ -33,6 +33,7 @@ config RISCV_VIRT
     select SIFIVE_PLIC
     select SIFIVE_TEST
     select VIRTIO_MMIO
+    select FW_CFG_DMA
 
 config SIFIVE_E
     bool
diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
index 0b39101a5e..e96ec4cbbc 100644
--- a/hw/riscv/virt.c
+++ b/hw/riscv/virt.c
@@ -53,6 +53,7 @@ static const MemMapEntry virt_memmap[] = {
     [VIRT_PLIC] =        {  0xc000000, VIRT_PLIC_SIZE(VIRT_CPUS_MAX * 2) },
     [VIRT_UART0] =       { 0x10000000,         0x100 },
     [VIRT_VIRTIO] =      { 0x10001000,        0x1000 },
+    [VIRT_FW_CFG] =      { 0x10100000,          0x18 },
     [VIRT_FLASH] =       { 0x20000000,     0x4000000 },
     [VIRT_PCIE_ECAM] =   { 0x30000000,    0x10000000 },
     [VIRT_PCIE_MMIO] =   { 0x40000000,    0x40000000 },
@@ -507,6 +508,28 @@ static inline DeviceState *gpex_pcie_init(MemoryRegion *sys_mem,
     return dev;
 }
 
+static FWCfgState *create_fw_cfg(const MachineState *mc)
+{
+    hwaddr base = virt_memmap[VIRT_FW_CFG].base;
+    hwaddr size = virt_memmap[VIRT_FW_CFG].size;
+    FWCfgState *fw_cfg;
+    char *nodename;
+
+    fw_cfg = fw_cfg_init_mem_wide(base + 8, base, 8, base + 16,
+                                  &address_space_memory);
+    fw_cfg_add_i16(fw_cfg, FW_CFG_NB_CPUS, (uint16_t)mc->smp.cpus);
+
+    nodename = g_strdup_printf("/fw-cfg@%" PRIx64, base);
+    qemu_fdt_add_subnode(mc->fdt, nodename);
+    qemu_fdt_setprop_string(mc->fdt, nodename,
+                            "compatible", "qemu,fw-cfg-mmio");
+    qemu_fdt_setprop_sized_cells(mc->fdt, nodename, "reg",
+                                 2, base, 2, size);
+    qemu_fdt_setprop(mc->fdt, nodename, "dma-coherent", NULL, 0);
+    g_free(nodename);
+    return fw_cfg;
+}
+
 static void virt_machine_init(MachineState *machine)
 {
     const MemMapEntry *memmap = virt_memmap;
@@ -688,6 +711,13 @@ static void virt_machine_init(MachineState *machine)
         start_addr = virt_memmap[VIRT_FLASH].base;
     }
 
+    /*
+     * Init fw_cfg.  Must be done before riscv_load_fdt, otherwise the device
+     * tree cannot be altered and we get FDT_ERR_NOSPACE.
+     */
+    s->fw_cfg = create_fw_cfg(machine);
+    rom_set_fw(s->fw_cfg);
+
     /* Compute the fdt load address in dram */
     fdt_load_addr = riscv_load_fdt(memmap[VIRT_DRAM].base,
                                    machine->ram_size, machine->fdt);
diff --git a/include/hw/riscv/virt.h b/include/hw/riscv/virt.h
index 632da52018..349fee1f89 100644
--- a/include/hw/riscv/virt.h
+++ b/include/hw/riscv/virt.h
@@ -40,6 +40,7 @@ struct RISCVVirtState {
     RISCVHartArrayState soc[VIRT_SOCKETS_MAX];
     DeviceState *plic[VIRT_SOCKETS_MAX];
     PFlashCFI01 *flash[2];
+    FWCfgState *fw_cfg;
 
     int fdt_size;
 };
@@ -53,6 +54,7 @@ enum {
     VIRT_PLIC,
     VIRT_UART0,
     VIRT_VIRTIO,
+    VIRT_FW_CFG,
     VIRT_FLASH,
     VIRT_DRAM,
     VIRT_PCIE_MMIO,
-- 
2.20.1