linux-kernel - [PATCH stable 5.4] ARM: Qualify enabling of swiotlb

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Date:   Wed, 22 Sep 2021 14:58:51 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     stable@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sasha Levin <sashal@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Russell King <linux@...linux.org.uk>,
        Linus Walleij <linus.walleij@...aro.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        linux-arm-kernel@...ts.infradead.org (moderated list:ARM PORT)
Subject: [PATCH stable 5.4] ARM: Qualify enabling of swiotlb_init()

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@...il.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.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