[PATCH 3/4] arm64: Default to 32-bit ZONE_DMA
From: Nicolas Saenz Julienne <hidden>
Date: 2020-10-01 16:18:11
Also in:
linux-devicetree, linux-iommu, linux-mm, lkml
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
The Raspberry Pi 4 needs two DMA zones as some of its devices can only DMA into the 30-bit physical address space. We solved that by creating an extra ZONE_DMA covering the 30-bit. It turns out that creating extra zones unnecessarily broke Kdump on large systems. So default to a single 32-bit wide ZONE_DMA and only define both zones if running on RPi4. Signed-off-by: Nicolas Saenz Julienne <redacted> --- arch/arm64/mm/init.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index e1a69a618832..3c3f462466eb 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c@@ -43,8 +43,6 @@ #include <asm/tlb.h> #include <asm/alternative.h> -#define ARM64_ZONE_DMA_BITS 30 - /* * We need to be able to catch inadvertent references to memstart_addr * that occur (potentially in generic code) before arm64_memblock_init()
@@ -388,8 +386,14 @@ void __init arm64_memblock_init(void) early_init_fdt_scan_reserved_mem(); if (IS_ENABLED(CONFIG_ZONE_DMA)) { - zone_dma_bits = ARM64_ZONE_DMA_BITS; - arm64_dma_phys_limit = max_zone_phys(ARM64_ZONE_DMA_BITS); + /* + * early_init_dt_scan() might alter zone_dma_bits based on the + * device's DT. Otherwise, have it cover the 32-bit address + * space. + */ + if (zone_dma_bits == ZONE_DMA_BITS_DEFAULT) + zone_dma_bits = 32; + arm64_dma_phys_limit = max_zone_phys(zone_dma_bits); } if (IS_ENABLED(CONFIG_ZONE_DMA32))
--
2.28.0
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