Re: [PATCH 07/16] hw/riscv/atlantis: Make UART unimp region a SoC device

[Daniel Henrique Barboza]

On 8/26/2026 7:05 PM, Joel Stanley wrote:

Make the unimplemented region covering the remainder of the console
UART's register space a SoC child device, mapped using a helper. This
makes it easier to map it into the SoC's memory container along with
the other devices in the future.

While here, rename the region from uart0 to uart1. The uart0 name was
a leftover from an earlier revision that used a different device for
the console.

Signed-off-by: Joel Stanley <j...@jms.id.au>
---

Reviewed-by: Daniel Henrique Barboza <daniel.barb...@oss.qualcomm.com>

  include/hw/riscv/tt_atlantis.h |  2 ++
  hw/riscv/tt_atlantis.c         | 19 ++++++++++++++++---
  2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/include/hw/riscv/tt_atlantis.h b/include/hw/riscv/tt_atlantis.h
index 7f7d4a5a5905..c9308aa57017 100644
--- a/include/hw/riscv/tt_atlantis.h
+++ b/include/hw/riscv/tt_atlantis.h
@@ -13,6 +13,7 @@
  #include "hw/core/sysbus.h"
  #include "hw/i2c/designware_i2c.h"
  #include "hw/intc/riscv_imsic.h"
+#include "hw/misc/unimp.h"
  #include "hw/riscv/riscv_hart.h"

#define TYPE_TT_ATLANTIS_MACHINE MACHINE_TYPE_NAME("tt-atlantis")

@@ -31,6 +32,7 @@ struct TTAtlantisState {
      RISCVHartArrayState soc;
      DeviceState *irqchip;
      DesignWareI2CState i2c[TT_ATL_NUM_I2C];
+    UnimplementedDeviceState uart1;

int fdt_size;

  };
diff --git a/hw/riscv/tt_atlantis.c b/hw/riscv/tt_atlantis.c
index 3f183db5c302..acfd0d31b368 100644
--- a/hw/riscv/tt_atlantis.c
+++ b/hw/riscv/tt_atlantis.c
@@ -409,6 +409,17 @@ static void load_fdt(TTAtlantisState *s)
      create_fdt_memory(s);
  }

+static void mmio_map_unimplemented(MemoryRegion *memory, SysBusDevice *dev,

+                                   const char *name, hwaddr addr, uint64_t 
size)
+{
+    qdev_prop_set_string(DEVICE(dev), "name", name);
+    qdev_prop_set_uint64(DEVICE(dev), "size", size);
+    sysbus_realize(dev, &error_abort);
+
+    memory_region_add_subregion_overlap(memory, addr,
+                                        sysbus_mmio_get_region(dev, 0), -1000);
+}
+
  static void tt_atlantis_machine_done(Notifier *notifier, void *data)
  {
      TTAtlantisState *s = container_of(notifier, TTAtlantisState, 
machine_done);
@@ -560,9 +571,11 @@ static void tt_atlantis_machine_init(MachineState *machine)
       * Create an unimplemented device region so writes don't fault
       * and reads return zero, which keeps Linux happy.
       */
-    create_unimplemented_device("tt-atlantis.uart0",
-                                s->memmap[TT_ATL_UART1].base,
-                                s->memmap[TT_ATL_UART1].size);
+    object_initialize_child(OBJECT(s), "uart1", &s->uart1,
+                            TYPE_UNIMPLEMENTED_DEVICE);
+    mmio_map_unimplemented(system_memory, SYS_BUS_DEVICE(&s->uart1),
+                           "tt-atlantis.uart1", s->memmap[TT_ATL_UART1].base,
+                           s->memmap[TT_ATL_UART1].size);

/* I2C */

      for (int i = 0; i < TT_ATL_NUM_I2C; i++) {