[PATCH v2 1/7] riscv/sifive_u: Add L2-LIM cache memory

[Alistair Francis]

On reset only a single L2 cache way is enabled, the others are exposed
as memory that can be used by early boot firmware. This L2 region is
generally disabled using the WayEnable register at a later stage in the
boot process. To allow firmware to target QEMU and the HiFive Unleashed
let's add the L2 LIM (LooselyIntegrated Memory).

Ideally we would want to adjust the size of this chunk of memory as the
L2 Cache Controller WayEnable register is incremented. Unfortunately I
don't see a nice way to handle reducing or blocking out the L2 LIM while
still allowing it be re returned to all enabled from a reset.

Signed-off-by: Alistair Francis <address@hidden>
---
 hw/riscv/sifive_u.c         | 16 ++++++++++++++++
 include/hw/riscv/sifive_u.h |  1 +
 2 files changed, 17 insertions(+)

diff --git a/hw/riscv/sifive_u.c b/hw/riscv/sifive_u.c
index 9f8e84bf2e..1d255ad13e 100644
--- a/hw/riscv/sifive_u.c
+++ b/hw/riscv/sifive_u.c
@@ -65,6 +65,7 @@ static const struct MemmapEntry {
     [SIFIVE_U_DEBUG] =    {        0x0,      0x100 },
     [SIFIVE_U_MROM] =     {     0x1000,    0x11000 },
     [SIFIVE_U_CLINT] =    {  0x2000000,    0x10000 },
+    [SIFIVE_U_L2LIM] =    {  0x8000000,  0x2000000 },
     [SIFIVE_U_PLIC] =     {  0xc000000,  0x4000000 },
     [SIFIVE_U_PRCI] =     { 0x10000000,     0x1000 },
     [SIFIVE_U_UART0] =    { 0x10010000,     0x1000 },
@@ -431,6 +432,7 @@ static void riscv_sifive_u_soc_realize(DeviceState *dev, 
Error **errp)
     const struct MemmapEntry *memmap = sifive_u_memmap;
     MemoryRegion *system_memory = get_system_memory();
     MemoryRegion *mask_rom = g_new(MemoryRegion, 1);
+    MemoryRegion *l2lim_mem = g_new(MemoryRegion, 1);
     qemu_irq plic_gpios[SIFIVE_U_PLIC_NUM_SOURCES];
     char *plic_hart_config;
     size_t plic_hart_config_len;
@@ -459,6 +461,20 @@ static void riscv_sifive_u_soc_realize(DeviceState *dev, 
Error **errp)
     memory_region_add_subregion(system_memory, memmap[SIFIVE_U_MROM].base,
                                 mask_rom);
 
+    /*
+     * Add L2-LIM at reset size.
+     * This should be reduced in size as the L2 Cache Controller WayEnable
+     * register is incremented. Unfortunately I don't see a nice (or any) way
+     * to handle reducing or blocking out the L2 LIM while still allowing it
+     * be re returned to all enabled after a reset. For the time being, just
+     * leave it enabled all the time. This won't break anything, but will be
+     * too generous to misbehaving guests.
+     */
+    memory_region_init_ram(l2lim_mem, NULL, "riscv.sifive.u.l2lim",
+                           memmap[SIFIVE_U_L2LIM].size, &error_fatal);
+    memory_region_add_subregion(system_memory, memmap[SIFIVE_U_L2LIM].base,
+                                l2lim_mem);
+
     /* create PLIC hart topology configuration string */
     plic_hart_config_len = (strlen(SIFIVE_U_PLIC_HART_CONFIG) + 1) *
                            ms->smp.cpus;
diff --git a/include/hw/riscv/sifive_u.h b/include/hw/riscv/sifive_u.h
index e4df298c23..50e3620c02 100644
--- a/include/hw/riscv/sifive_u.h
+++ b/include/hw/riscv/sifive_u.h
@@ -58,6 +58,7 @@ enum {
     SIFIVE_U_DEBUG,
     SIFIVE_U_MROM,
     SIFIVE_U_CLINT,
+    SIFIVE_U_L2LIM,
     SIFIVE_U_PLIC,
     SIFIVE_U_PRCI,
     SIFIVE_U_UART0,
-- 
2.23.0