From: Paul Burton <paul.burton@imgtec.com>
Date: Mon, 5 Sep 2016 15:24:54 +0100
Subject: [PATCH] MIPS: c-r4k: Fix size calc when avoiding IPIs for small
 icache flushes

Commit f70ddc07b637 ("MIPS: c-r4k: Avoid small flush_icache_range SMP
calls") adds checks to force use of hit-type cache ops for small icache
flushes where they are globalised & index-type cache ops aren't, in
order to avoid the overhead of IPIs in those cases. However it
calculated the size of the region being flushed incorrectly, subtracting
the end address from the start address rather than the reverse. This
would have led to an overflow with size wrapping round to some large
value, and likely to the special case for avoiding IPIs not actually
being hit.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Fixes: f70ddc07b637 ("MIPS: c-r4k: Avoid small flush_icache_range SMP calls")
Reviewed-by: James Hogan <james.hogan@imgtec.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Cc: Huacai Chen <chenhc@lemote.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/14211/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
---

--- a/arch/mips/mm/c-r4k.c
+++ b/arch/mips/mm/c-r4k.c
@@ -781,7 +781,7 @@ static void r4k_flush_icache_range(unsig
 		 * If address-based cache ops are globalized, then we may be
 		 * able to avoid the IPI for small flushes.
 		 */
-		size = start - end;
+		size = end - start;
 		cache_size = icache_size;
 		if (!cpu_has_ic_fills_f_dc) {
 			size *= 2;