On 8/26/2026 11:53 AM, Anirudh Srinivasan wrote:
Hi Daniel,
On Tue, Aug 25, 2026 at 4:24 PM Daniel Henrique Barboza
<[email protected]> wrote:
Add a common uart FDT helper to be used by 'virt' and 'tt-atlantis'.
To accomodate both boards the helper is doing the following:
- an 'additional_reg_props' flag is used to control whether we want
'reg-shift' and 'reg-io-width' elements added. OpenSBI won't boot
with the tt-atlantis board without them, but 'virt' can't deal with
them being added unconditionally either.
- an 'is_serial0' flag is added to control whether we need to set
additional properties related to the first serial. This is required
because the 'virt' board adds two uarts in the FDT.
No FDT changes intended.
Signed-off-by: Daniel Henrique Barboza <[email protected]>
---
hw/riscv/fdt-common.c | 39 +++++++++++++++++++++++++++++++
hw/riscv/tt_atlantis.c | 21 +----------------
hw/riscv/virt.c | 44 +++++++----------------------------
include/hw/riscv/fdt-common.h | 4 ++++
4 files changed, 52 insertions(+), 56 deletions(-)
diff --git a/hw/riscv/fdt-common.c b/hw/riscv/fdt-common.c
index f31cc9d3cc..b3f3af3762 100644
--- a/hw/riscv/fdt-common.c
+++ b/hw/riscv/fdt-common.c
@@ -791,3 +791,42 @@ void create_fdt_socket_aclint(void *fdt, ACLINTFdtProps
*props,
g_free(name);
}
}
+
+void create_fdt_uart(void *fdt, const MemMapEntry *uart_mem,
+ int uart_irq, int aia_type,
+ bool additional_reg_props, bool is_serial0,
+ uint32_t irq_mmio_phandle)
+{
+ g_autofree char *name = NULL;
+
+ name = g_strdup_printf("/soc/serial@%"HWADDR_PRIx, uart_mem->base);
+ qemu_fdt_add_subnode(fdt, name);
+ qemu_fdt_setprop_string(fdt, name, "compatible", "ns16550a");
+ qemu_fdt_setprop_sized_cells(fdt, name, "reg",
+ 2, uart_mem->base,
+ 2, uart_mem->size);
+
+ /*
+ * The tt-atlantis board requires these extra props in the
+ * DT, but adding them unconditionally will break OpenSBI
+ * for 'virt'.
+ */
+ if (additional_reg_props) {
+ qemu_fdt_setprop_cell(fdt, name, "reg-shift", 2);
+ qemu_fdt_setprop_cell(fdt, name, "reg-io-width", 4);
+ }
I think the issue is that atlantis uses a uart that has 32 bit
register spacing (0x0, 0x4, 0x8, 0xc....) rather than 8 bit spacing
(0x0, 0x1, 0x2...). So rather than "additional_reg_props", would a
name like "word_addressing" or "32_bit_spacing" make sense?
Works for me. I'll rename it in v2.
Thanks,
Daniel
Regards
Anirudh Srinivasan
