[PATCH stable 5.4] ARM: Qualify enabling of swiotlb_init()

[Florian Fainelli]

commit fcf044891c84e38fc90eb736b818781bccf94e38 upstream

We do not need a SWIOTLB unless we have DRAM that is addressable beyond
the arm_dma_limit. Compare max_pfn with arm_dma_pfn_limit to determine
whether we do need a SWIOTLB to be initialized.

Fixes: ad3c7b18c5b3 ("arm: use swiotlb for bounce buffering on LPAE configs")
Signed-off-by: Florian Fainelli <f.fainelli at gmail.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
---
 arch/arm/mm/init.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 0804a6af4a3b..5a3641b5ec2c 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -469,7 +469,11 @@ static void __init free_highpages(void)
 void __init mem_init(void)
 {
 #ifdef CONFIG_ARM_LPAE
-	swiotlb_init(1);
+	if (swiotlb_force == SWIOTLB_FORCE ||
+	    max_pfn > arm_dma_pfn_limit)
+		swiotlb_init(1);
+	else
+		swiotlb_force = SWIOTLB_NO_FORCE;
 #endif
 
 	set_max_mapnr(pfn_to_page(max_pfn) - mem_map);
-- 
2.25.1