powerpc: Move default hash table size calculation to hash_utils_64.c

We weren't computing the size of the hash table correctly on iSeries
because the relevant code in prom.c was #ifdef CONFIG_PPC_PSERIES.
This moves the code to hash_utils_64.c, makes it unconditional, and
cleans it up a bit.
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/prom.c

@@ -1323,26 +1323,6 @@ void __init early_init_devtree(void *params)
 	 */
 	scan_flat_dt(early_init_dt_scan_cpus, NULL);
 
-#ifdef CONFIG_PPC_PSERIES
-	/* If hash size wasn't obtained above, we calculate it now based on
-	 * the total RAM size
-	 */
-	if (ppc64_pft_size == 0) {
-		unsigned long rnd_mem_size, pteg_count;
-
-		/* round mem_size up to next power of 2 */
-		rnd_mem_size = 1UL << __ilog2(systemcfg->physicalMemorySize);
-		if (rnd_mem_size < systemcfg->physicalMemorySize)
-			rnd_mem_size <<= 1;
-
-		/* # pages / 2 */
-		pteg_count = max(rnd_mem_size >> (12 + 1), 1UL << 11);
-
-		ppc64_pft_size = __ilog2(pteg_count << 7);
-	}
-
-	DBG("Hash pftSize: %x\n", (int)ppc64_pft_size);
-#endif
 	DBG(" <- early_init_devtree()\n");
 }
 

arch/powerpc/mm/hash_utils_64.c

@@ -155,6 +155,27 @@ static inline void create_pte_mapping(unsigned long start, unsigned long end,
 	}
 }
 
+static unsigned long get_hashtable_size(void)
+{
+	unsigned long rnd_mem_size, pteg_count;
+
+	/* If hash size wasn't obtained in prom.c, we calculate it now based on
+	 * the total RAM size
+	 */
+	if (ppc64_pft_size)
+		return 1UL << ppc64_pft_size;
+
+	/* round mem_size up to next power of 2 */
+	rnd_mem_size = 1UL << __ilog2(systemcfg->physicalMemorySize);
+	if (rnd_mem_size < systemcfg->physicalMemorySize)
+		rnd_mem_size <<= 1;
+
+	/* # pages / 2 */
+	pteg_count = max(rnd_mem_size >> (12 + 1), 1UL << 11);
+
+	return pteg_count << 7;
+}
+
 void __init htab_initialize(void)
 {
 	unsigned long table, htab_size_bytes;
@@ -170,7 +191,7 @@ void __init htab_initialize(void)
 	 * Calculate the required size of the htab.  We want the number of
 	 * PTEGs to equal one half the number of real pages.
 	 */ 
-	htab_size_bytes = 1UL << ppc64_pft_size;
+	htab_size_bytes = get_hashtable_size();
 	pteg_count = htab_size_bytes >> 7;
 
 	/* For debug, make the HTAB 1/8 as big as it normally would be. */