Add comment about handling of c0_pagemask in Linux and a R4600 1.7 bug.

1 files changed, 8 insertions, 0 deletions

diff --git a/arch/mips/mm/r4xx0.c b/arch/mips/mm/r4xx0.c
index f83f41df8..974343069 100644
--- a/arch/mips/mm/r4xx0.c
+++ b/arch/mips/mm/r4xx0.c
@@ -2432,6 +2432,14 @@ try_again:
 
 	flush_cache_all();
 	write_32bit_cp0_register(CP0_WIRED, 0);
+
+	/*
+	 * You should never change this register:
+	 *   - On R4600 1.7 the tlbp never hits for pages smaller than
+	 *     the value in the c0_pagemask register.
+	 *   - The entire mm handling assumes the c0_pagemask register to
+	 *     be set for 4kb pages.
+	 */
 	write_32bit_cp0_register(CP0_PAGEMASK, PM_4K);
 	flush_tlb_all();
 }