ppc/pnv: Implement LPC FW address space IDSEL

LPC FW address space is a 256MB (28-bit) region to one of 16-devices
that are selected with the IDSEL register. Implement this by making
the ISA FW address space 4GB, and move the 256MB OPB alias within
that space according to IDSEL.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

hw/ppc/pnv_lpc.c

@@ -85,7 +85,7 @@ enum {
 
 #define ISA_IO_SIZE             0x00010000
 #define ISA_MEM_SIZE            0x10000000
-#define ISA_FW_SIZE             0x10000000
+#define ISA_FW_SIZE             0x100000000
 #define LPC_IO_OPB_ADDR         0xd0010000
 #define LPC_IO_OPB_SIZE         0x00010000
 #define LPC_MEM_OPB_ADDR        0xe0000000
@@ -561,10 +561,13 @@ static void lpc_hc_write(void *opaque, hwaddr addr, uint64_t val,
 
     switch (addr) {
     case LPC_HC_FW_SEG_IDSEL:
-        /* XXX Actually figure out how that works as this impact
-         * memory regions/aliases
+        /*
+         * ISA FW "devices" are modeled as 16x256MB windows into a
+         * 4GB LPC FW address space.
          */
+        val &= 0xf; /* Selects device 0-15 */
         lpc->lpc_hc_fw_seg_idsel = val;
+        memory_region_set_alias_offset(&lpc->opb_isa_fw, val * LPC_FW_OPB_SIZE);
         break;
     case LPC_HC_FW_RD_ACC_SIZE:
         lpc->lpc_hc_fw_rd_acc_size = val;
@@ -798,9 +801,9 @@ static void pnv_lpc_realize(DeviceState *dev, Error **errp)
     memory_region_init(&lpc->opb_mr, OBJECT(dev), "lpc-opb", 0x100000000ull);
     address_space_init(&lpc->opb_as, &lpc->opb_mr, "lpc-opb");
 
-    /* Create ISA IO and Mem space regions which are the root of
-     * the ISA bus (ie, ISA address spaces). We don't create a
-     * separate one for FW which we alias to memory.
+    /*
+     * Create ISA IO, Mem, and FW space regions which are the root of
+     * the ISA bus (ie, ISA address spaces).
      */
     memory_region_init(&lpc->isa_io, OBJECT(dev), "isa-io", ISA_IO_SIZE);
     memory_region_init(&lpc->isa_mem, OBJECT(dev), "isa-mem", ISA_MEM_SIZE);