MIPS: WARN_ON invalid DMA cache maintenance, not BUG_ON

BugLink: https://bugs.launchpad.net/bugs/1798539

[ Upstream commit d4da0e97 ]

If a driver causes DMA cache maintenance with a zero length then we
currently BUG and kill the kernel. As this is a scenario that we may
well be able to recover from, WARN & return in the condition instead.
Signed-off-by: Paul Burton <paul.burton@mips.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Patchwork: https://patchwork.linux-mips.org/patch/14623/
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

arch/mips/mm/c-r4k.c

@@ -712,7 +712,8 @@ static void r4k_flush_icache_range(unsigned long start, unsigned long end)
 static void r4k_dma_cache_wback_inv(unsigned long addr, unsigned long size)
 {
 	/* Catch bad driver code */
-	BUG_ON(size == 0);
+	if (WARN_ON(size == 0))
+		return;
 
 	preempt_disable();
 	if (cpu_has_inclusive_pcaches) {
@@ -745,7 +746,8 @@ static void r4k_dma_cache_wback_inv(unsigned long addr, unsigned long size)
 static void r4k_dma_cache_inv(unsigned long addr, unsigned long size)
 {
 	/* Catch bad driver code */
-	BUG_ON(size == 0);
+	if (WARN_ON(size == 0))
+		return;
 
 	preempt_disable();
 	if (cpu_has_inclusive_pcaches) {