diff --git a/grub-core/kern/ieee1275/cmain.c b/grub-core/kern/ieee1275/cmain.c
index 4442b6a83..400d85d28 100644
--- a/grub-core/kern/ieee1275/cmain.c
+++ b/grub-core/kern/ieee1275/cmain.c
@@ -123,6 +123,11 @@ grub_ieee1275_find_options (void)
 	      break;
 	    }
 	}
+
+#if defined(__powerpc__)
+      if (grub_strncmp (tmp, "IBM,", 4) == 0)
+	grub_ieee1275_set_flag (GRUB_IEEE1275_FLAG_CAN_TRY_CAS_FOR_MORE_MEMORY);
+#endif
     }
 
   if (is_smartfirmware)
diff --git a/grub-core/kern/ieee1275/init.c b/grub-core/kern/ieee1275/init.c
index 2adf4fdfc..0bc571e3e 100644
--- a/grub-core/kern/ieee1275/init.c
+++ b/grub-core/kern/ieee1275/init.c
@@ -200,11 +200,176 @@ heap_init (grub_uint64_t addr, grub_uint64_t len, grub_memory_type_t type,
   return 0;
 }
 
+/*
+ * How much memory does OF believe it has? (regardless of whether
+ * it's accessible or not)
+ */
+static grub_err_t
+grub_ieee1275_total_mem (grub_uint64_t *total)
+{
+  grub_ieee1275_phandle_t root;
+  grub_ieee1275_phandle_t memory;
+  grub_uint32_t reg[4];
+  grub_ssize_t reg_size;
+  grub_uint32_t address_cells = 1;
+  grub_uint32_t size_cells = 1;
+  grub_uint64_t size;
+
+  /* If we fail to get to the end, report 0. */
+  *total = 0;
+
+  /* Determine the format of each entry in `reg'.  */
+  if (grub_ieee1275_finddevice ("/", &root))
+    return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "couldn't find / node");
+  if (grub_ieee1275_get_integer_property (root, "#address-cells", &address_cells,
+					  sizeof (address_cells), 0))
+    return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "couldn't examine #address-cells");
+  if (grub_ieee1275_get_integer_property (root, "#size-cells", &size_cells,
+					  sizeof (size_cells), 0))
+    return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "couldn't examine #size-cells");
+
+  if (size_cells > address_cells)
+    address_cells = size_cells;
+
+  /* Load `/memory/reg'.  */
+  if (grub_ieee1275_finddevice ("/memory", &memory))
+    return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "couldn't find /memory node");
+  if (grub_ieee1275_get_integer_property (memory, "reg", reg,
+					  sizeof (reg), &reg_size))
+    return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "couldn't examine /memory/reg property");
+  if (reg_size < 0 || (grub_size_t) reg_size > sizeof (reg))
+    return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "/memory response buffer exceeded");
+
+  if (grub_ieee1275_test_flag (GRUB_IEEE1275_FLAG_BROKEN_ADDRESS_CELLS))
+    {
+      address_cells = 1;
+      size_cells = 1;
+    }
+
+  /* Decode only the size */
+  size = reg[address_cells];
+  if (size_cells == 2)
+    size = (size << 32) | reg[address_cells + 1];
+
+  *total = size;
+
+  return grub_errno;
+}
+
+#if defined(__powerpc__)
+
+/* See PAPR or arch/powerpc/kernel/prom_init.c */
+struct option_vector2
+{
+  grub_uint8_t byte1;
+  grub_uint16_t reserved;
+  grub_uint32_t real_base;
+  grub_uint32_t real_size;
+  grub_uint32_t virt_base;
+  grub_uint32_t virt_size;
+  grub_uint32_t load_base;
+  grub_uint32_t min_rma;
+  grub_uint32_t min_load;
+  grub_uint8_t min_rma_percent;
+  grub_uint8_t max_pft_size;
+} GRUB_PACKED;
+
+struct pvr_entry
+{
+  grub_uint32_t mask;
+  grub_uint32_t entry;
+};
+
+struct cas_vector
+{
+  struct
+  {
+    struct pvr_entry terminal;
+  } pvr_list;
+  grub_uint8_t num_vecs;
+  grub_uint8_t vec1_size;
+  grub_uint8_t vec1;
+  grub_uint8_t vec2_size;
+  struct option_vector2 vec2;
+  grub_uint8_t vec3_size;
+  grub_uint16_t vec3;
+  grub_uint8_t vec4_size;
+  grub_uint16_t vec4;
+} GRUB_PACKED;
+
+/*
+ * Call ibm,client-architecture-support to try to get more RMA.
+ * We ask for 512MB which should be enough to verify a distro kernel.
+ * We ignore most errors: if we don't succeed we'll proceed with whatever
+ * memory we have.
+ */
+static void
+grub_ieee1275_ibm_cas (void)
+{
+  int rc;
+  grub_ieee1275_ihandle_t root;
+  struct cas_args
+  {
+    struct grub_ieee1275_common_hdr common;
+    grub_ieee1275_cell_t method;
+    grub_ieee1275_ihandle_t ihandle;
+    grub_ieee1275_cell_t cas_addr;
+    grub_ieee1275_cell_t result;
+  } args;
+  struct cas_vector vector =
+  {
+    .pvr_list = { { 0x00000000, 0xffffffff } }, /* any processor */
+    .num_vecs = 4 - 1,
+    .vec1_size = 0,
+    .vec1 = 0x80, /* ignore */
+    .vec2_size = 1 + sizeof (struct option_vector2) - 2,
+    .vec2 = {
+      0, 0, -1, -1, -1, -1, -1, 512, -1, 0, 48
+    },
+    .vec3_size = 2 - 1,
+    .vec3 = 0x00e0, /* ask for FP + VMX + DFP but don't halt if unsatisfied */
+    .vec4_size = 2 - 1,
+    .vec4 = 0x0001, /* set required minimum capacity % to the lowest value */
+  };
+
+  INIT_IEEE1275_COMMON (&args.common, "call-method", 3, 2);
+  args.method = (grub_ieee1275_cell_t) "ibm,client-architecture-support";
+  rc = grub_ieee1275_open ("/", &root);
+  if (rc)
+    {
+      grub_error (GRUB_ERR_IO, "could not open root when trying to call CAS");
+      return;
+    }
+  args.ihandle = root;
+  args.cas_addr = (grub_ieee1275_cell_t) &vector;
+
+  grub_printf ("Calling ibm,client-architecture-support from grub...");
+  IEEE1275_CALL_ENTRY_FN (&args);
+  grub_printf ("done\n");
+
+  grub_ieee1275_close (root);
+}
+
+#endif /* __powerpc__ */
+
 static void
 grub_claim_heap (void)
 {
   unsigned long total = 0;
 
+#if defined(__powerpc__)
+  if (grub_ieee1275_test_flag (GRUB_IEEE1275_FLAG_CAN_TRY_CAS_FOR_MORE_MEMORY))
+    {
+      grub_uint64_t rma_size;
+      grub_err_t err;
+
+      err = grub_ieee1275_total_mem (&rma_size);
+      /* if we have an error, don't call CAS, just hope for the best */
+      if (err == GRUB_ERR_NONE && rma_size < (512 * 1024 * 1024))
+	grub_ieee1275_ibm_cas ();
+    }
+#endif
+
   grub_machine_mmap_iterate (heap_init, &total);
 }
 #endif
diff --git a/include/grub/ieee1275/ieee1275.h b/include/grub/ieee1275/ieee1275.h
index f53228703..77e4e61e5 100644
--- a/include/grub/ieee1275/ieee1275.h
+++ b/include/grub/ieee1275/ieee1275.h
@@ -128,6 +128,16 @@ enum grub_ieee1275_flag
   GRUB_IEEE1275_FLAG_CURSORONOFF_ANSI_BROKEN,
 
   GRUB_IEEE1275_FLAG_RAW_DEVNAMES,
+
+#if defined(__powerpc__)
+  /*
+   * On PFW, the first time we boot a Linux partition, we may only get 256MB of
+   * real memory area, even if the partition has more memory. Set this flag if
+   * we think we're running under PFW. Then, if this flag is set, and the RMA is
+   * only 256MB in size, try asking for more with CAS.
+   */
+  GRUB_IEEE1275_FLAG_CAN_TRY_CAS_FOR_MORE_MEMORY,
+#endif
 };
 
 extern int EXPORT_FUNC(grub_ieee1275_test_flag) (enum grub_ieee1275_flag flag);