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From:   Florian Fainelli <f.fainelli@gmail.com>
To:     linux-arm-kernel@lists.infradead.org
Cc:     Florian Fainelli <f.fainelli@gmail.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Christoph Hellwig <hch@lst.de>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Robin Murphy <robin.murphy@arm.com>,
        iommu@lists.linux-foundation.org (open list:SWIOTLB SUBSYSTEM),
        linux-kernel@vger.kernel.org (open list),
        Russell King <linux@armlinux.org.uk>,
        Mike Rapoport <rppt@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Ard Biesheuvel <ardb@kernel.org>,
        Max Filippov <jcmvbkbc@gmail.com>,
        Catalin Marinas <catalin.marinas@arm.com>, opendmb@gmail.com
Subject: [PATCH] ARM: Qualify enabling of swiotlb_init()
Date:   Thu, 18 Mar 2021 21:03:33 -0700
Message-Id: <20210319040333.183827-1-f.fainelli@gmail.com>
MIME-Version: 1.0
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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@gmail.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 828a2561b229..8356bf1daa28 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -301,7 +301,11 @@ 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