powerpc/64: pcpu setup avoid reading mmu_linear_psize on 64e or radix

Radix never sets mmu_linear_psize so it's always 4K, which causes pcpu
atom_size to always be PAGE_SIZE. 64e sets it to 1GB always.

Make paths for these platforms to be explicit about what value they set
atom_size to.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211201144153.2456614-12-npiggin@gmail.com

arch/powerpc/kernel/setup_64.c

@@ -880,14 +880,23 @@ void __init setup_per_cpu_areas(void)
 	int rc = -EINVAL;
 
 	/*
-	 * Linear mapping is one of 4K, 1M and 16M.  For 4K, no need
-	 * to group units.  For larger mappings, use 1M atom which
-	 * should be large enough to contain a number of units.
+	 * BookE and BookS radix are historical values and should be revisited.
 	 */
-	if (mmu_linear_psize == MMU_PAGE_4K)
+	if (IS_ENABLED(CONFIG_PPC_BOOK3E)) {
+		atom_size = SZ_1M;
+	} else if (radix_enabled()) {
 		atom_size = PAGE_SIZE;
-	else
-		atom_size = 1 << 20;
+	} else {
+		/*
+		 * Linear mapping is one of 4K, 1M and 16M.  For 4K, no need
+		 * to group units.  For larger mappings, use 1M atom which
+		 * should be large enough to contain a number of units.
+		 */
+		if (mmu_linear_psize == MMU_PAGE_4K)
+			atom_size = PAGE_SIZE;
+		else
+			atom_size = SZ_1M;
+	}
 
 	if (pcpu_chosen_fc != PCPU_FC_PAGE) {
 		rc = pcpu_embed_first_chunk(0, dyn_size, atom_size, pcpu_cpu_distance,