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Subject[PATCH] [PATCH] ARM64: Setup DMA32 zone size by bootargs
Date
this patch allowing the DMA32 zone be configurable in ARM64.

Signed-off-by: Alix Wu <alix.wu@mediatek.com>
Signed-off-by: YJ Chiang <yj.chiang@mediatek.com>
Signed-off-by: Phil Chang <phil.chang@mediatek.com>
---
For some devices, the main memory split into 2 part due to the memory
architecture, the efficient and less inefficient part.
One of the use case is fine-tune the dma32 size to contain all the
efficient part of memory block on this kind of architecture

.../admin-guide/kernel-parameters.txt | 3 +++
arch/arm64/include/asm/memory.h | 2 ++
arch/arm64/mm/init.c | 26 ++++++++++++++++++-
3 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index bdc1f33fd3d1..ef3bc3d4931a 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -980,6 +980,9 @@
The filter can be disabled or changed to another
driver later using sysfs.

+ dma32_size=nn[KMG] [KNL,BOOT,ARM64]
+ Forces the DMA32 zone size of <nn> in MB.
+
driver_async_probe= [KNL]
List of driver names to be probed asynchronously.
Format: <driver_name1>,<driver_name2>...
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index afa722504bfd..710de08ae8ae 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -175,6 +175,8 @@ extern u64 kimage_vaddr;
/* the offset between the kernel virtual and physical mappings */
extern u64 kimage_voffset;

+extern phys_addr_t dma32_zone_size;
+
static inline unsigned long kaslr_offset(void)
{
return kimage_vaddr - KIMAGE_VADDR;
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 481d22c32a2e..fd1b85e131cc 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -60,6 +60,9 @@ EXPORT_SYMBOL(physvirt_offset);
struct page *vmemmap __ro_after_init;
EXPORT_SYMBOL(vmemmap);

+phys_addr_t dma32_zone_size __ro_after_init;
+EXPORT_SYMBOL(dma32_zone_size);
+
/*
* We create both ZONE_DMA and ZONE_DMA32. ZONE_DMA covers the first 1G of
* memory as some devices, namely the Raspberry Pi 4, have peripherals with
@@ -189,7 +192,12 @@ static void __init reserve_elfcorehdr(void)
static phys_addr_t __init max_zone_phys(unsigned int zone_bits)
{
phys_addr_t offset = memblock_start_of_DRAM() & GENMASK_ULL(63, zone_bits);
- return min(offset + (1ULL << zone_bits), memblock_end_of_DRAM());
+ phys_addr_t zone_size = (1ULL << zone_bits);
+
+ if (IS_ENABLED(CONFIG_ZONE_DMA32) && zone_bits == 32 && dma32_zone_size)
+ zone_size = min(zone_size, dma32_zone_size);
+
+ return min(offset + zone_size, memblock_end_of_DRAM());
}

static void __init zone_sizes_init(unsigned long min, unsigned long max)
@@ -242,6 +250,22 @@ static int __init early_mem(char *p)
}
early_param("mem", early_mem);

+static int __init setup_dma32_zone(char *p)
+{
+ unsigned long long size = memparse(p, NULL);
+
+ /* DMA32 zone size should never grater than 4G */
+ if (size > SZ_4G)
+ return -EINVAL;
+
+ pr_notice("Setup dma32 zone size to %llu Mb\n", size >> 20);
+ dma32_zone_size = size;
+
+ return 0;
+}
+
+early_param("dma32_size", setup_dma32_zone);
+
static int __init early_init_dt_scan_usablemem(unsigned long node,
const char *uname, int depth, void *data)
{
--
2.18.0
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