[PATCH] [PATCH] ARM64: Setup DMA32 zone size by bootargs

[Phil Chang]

Allowing the DMA32 zone be configurable in ARM64 but at most 4Gb.

Signed-off-by: Alix Wu <alix...@mediatek.com>
Signed-off-by: YJ Chiang <yj.chi...@mediatek.com>
Signed-off-by: Phil Chang <phil.ch...@mediatek.com>
---

 .../admin-guide/kernel-parameters.txt         |  3 ++
 arch/arm64/include/asm/memory.h               |  2 +
 arch/arm64/mm/init.c                          | 39 +++++++++++++++++--
 3 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt 
b/Documentation/admin-guide/kernel-parameters.txt
index bdc1f33fd3d1..5be6259e9ba8 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[MG]  [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..c8af53680d46 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
@@ -242,6 +245,29 @@ static int __init early_mem(char *p)
 }
 early_param("mem", early_mem);
 
+static int __init setup_dma32_zone(char *p)
+{
+       u64 size;
+
+       if (!p)
+               return -EINVAL;
+
+       if (kstrtoull(p, 0, &size))
+               return -EINVAL;
+
+       /* DMA32 zone size should never grater than 4G */
+       if (size > max_zone_phys(32) / SZ_1M)
+               return -EINVAL;
+
+       pr_notice("Setup dma32 zone size to %llu Mb\n", size);
+
+       dma32_zone_size = size * SZ_1M;
+
+       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)
 {
@@ -392,10 +418,17 @@ void __init arm64_memblock_init(void)
                arm64_dma_phys_limit = max_zone_phys(ARM64_ZONE_DMA_BITS);
        }
 
-       if (IS_ENABLED(CONFIG_ZONE_DMA32))
-               arm64_dma32_phys_limit = max_zone_phys(32);
-       else
+       if (IS_ENABLED(CONFIG_ZONE_DMA32)) {
+               if (dma32_zone_size) {
+                       arm64_dma32_phys_limit = min(max_zone_phys(32),
+                               dma32_zone_size + memblock_start_of_DRAM());
+               } else {
+                       arm64_dma32_phys_limit = max_zone_phys(32);
+                       dma32_zone_size = arm64_dma32_phys_limit;
+               }
+       } else {
                arm64_dma32_phys_limit = PHYS_MASK + 1;
+       }
 
        reserve_crashkernel();
 
-- 
2.18.0