From: Jamin Lin <jamin_lin@aspeedtech.com>

AST2700 has a 128KB SRAM, physically mapped at 0x10000000–0x1001FFFF for
the PSP (CA35) processor. The TSP coprocessor shares this same SRAM but
accesses it through a different address window at 0x70000000–0x7001FFFF.

To model this shared-memory behavior in QEMU, this commit introduces a
linked SRAM property and alias mapping between the PSP and TSP subsystems.

Changes include:
- Add the SRAM alias mapping at 0x70000000 in aspeed_ast27x0-tsp.c.
- In aspeed_ast27x0-fc.c, connect the TSP coprocessor’s "sram" link to
  the PSP’s SRAM region.
- Ensure the alias region is initialized during TSP SoC realization so
  the TSP can correctly access shared SRAM through its own address space.

This ensures that the TSP and PSP share the same physical SRAM backing.

Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20251015062210.3128710-5-jamin_lin@aspeedtech.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
---
 hw/arm/aspeed_ast27x0-fc.c  | 4 ++++
 hw/arm/aspeed_ast27x0-tsp.c | 7 +++++++
 2 files changed, 11 insertions(+)

diff --git a/hw/arm/aspeed_ast27x0-fc.c b/hw/arm/aspeed_ast27x0-fc.c
index 25e668a648fa..dfac7d1e17b8 100644
--- a/hw/arm/aspeed_ast27x0-fc.c
+++ b/hw/arm/aspeed_ast27x0-fc.c
@@ -150,6 +150,8 @@ static bool ast2700fc_tsp_init(MachineState *machine, Error **errp)
     AspeedCoprocessorState *soc;
     AspeedCoprocessorClass *sc;
     Ast2700FCState *s = AST2700A1FC(machine);
+    AspeedSoCState *psp = ASPEED_SOC(&s->ca35);
+
     s->tsp_sysclk = clock_new(OBJECT(s), "TSP_SYSCLK");
     clock_set_hz(s->tsp_sysclk, 200000000ULL);
 
@@ -166,6 +168,8 @@ static bool ast2700fc_tsp_init(MachineState *machine, Error **errp)
     sc = ASPEED_COPROCESSOR_GET_CLASS(soc);
     aspeed_soc_uart_set_chr(soc->uart, ASPEED_DEV_UART7, sc->uarts_base,
                             sc->uarts_num, serial_hd(2));
+    object_property_set_link(OBJECT(&s->tsp), "sram",
+                             OBJECT(&psp->sram), &error_abort);
     if (!qdev_realize(DEVICE(&s->tsp), NULL, errp)) {
         return false;
     }
diff --git a/hw/arm/aspeed_ast27x0-tsp.c b/hw/arm/aspeed_ast27x0-tsp.c
index caeb3392a8e6..56b68adf541b 100644
--- a/hw/arm/aspeed_ast27x0-tsp.c
+++ b/hw/arm/aspeed_ast27x0-tsp.c
@@ -20,6 +20,7 @@
 
 static const hwaddr aspeed_soc_ast27x0tsp_memmap[] = {
     [ASPEED_DEV_SDRAM]     =  0x00000000,
+    [ASPEED_DEV_SRAM]      =  0x70000000,
     [ASPEED_DEV_INTC]      =  0x72100000,
     [ASPEED_DEV_SCU]       =  0x72C02000,
     [ASPEED_DEV_SCUIO]     =  0x74C02000,
@@ -195,6 +196,12 @@ static void aspeed_soc_ast27x0tsp_realize(DeviceState *dev_soc, Error **errp)
                                 sc->memmap[ASPEED_DEV_SDRAM],
                                 &s->sdram);
 
+    /* SRAM */
+    memory_region_init_alias(&s->sram_alias, OBJECT(s), "sram.alias",
+                             s->sram, 0, memory_region_size(s->sram));
+    memory_region_add_subregion(s->memory, sc->memmap[ASPEED_DEV_SRAM],
+                                &s->sram_alias);
+
     /* SCU */
     if (!sysbus_realize(SYS_BUS_DEVICE(&s->scu), errp)) {
         return;
-- 
2.51.0