[PATCH 6/8] dma-direct: turn ARCH_ZONE_DMA_BITS into a variable

[Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>]

Some architectures, notably arm64, are interested in tweaking this
depending on their runtime dma addressing limitations.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
---

 arch/powerpc/include/asm/page.h |  9 ---------
 arch/powerpc/mm/mem.c           | 14 ++++++++++++--
 arch/s390/include/asm/page.h    |  2 --
 arch/s390/mm/init.c             |  1 +
 include/linux/dma-direct.h      |  2 ++
 kernel/dma/direct.c             |  8 +++-----
 6 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
index 0d52f57fca04..73668a21ae78 100644
--- a/arch/powerpc/include/asm/page.h
+++ b/arch/powerpc/include/asm/page.h
@@ -319,13 +319,4 @@ struct vm_area_struct;
 #endif /* __ASSEMBLY__ */
 #include <asm/slice.h>
 
-/*
- * Allow 30-bit DMA for very limited Broadcom wifi chips on many powerbooks.
- */
-#ifdef CONFIG_PPC32
-#define ARCH_ZONE_DMA_BITS 30
-#else
-#define ARCH_ZONE_DMA_BITS 31
-#endif
-
 #endif /* _ASM_POWERPC_PAGE_H */
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 9191a66b3bc5..3792a998ca02 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -31,6 +31,7 @@
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 #include <linux/memremap.h>
+#include <linux/dma-direct.h>
 
 #include <asm/pgalloc.h>
 #include <asm/prom.h>
@@ -201,7 +202,7 @@ static int __init mark_nonram_nosave(void)
  * everything else. GFP_DMA32 page allocations automatically fall back to
  * ZONE_DMA.
  *
- * By using 31-bit unconditionally, we can exploit ARCH_ZONE_DMA_BITS to
+ * By using 31-bit unconditionally, we can exploit arch_zone_dma_bits to
  * inform the generic DMA mapping code.  32-bit only devices (if not handled
  * by an IOMMU anyway) will take a first dip into ZONE_NORMAL and get
  * otherwise served by ZONE_DMA.
@@ -237,9 +238,18 @@ void __init paging_init(void)
 	printk(KERN_DEBUG "Memory hole size: %ldMB\n",
 	       (long int)((top_of_ram - total_ram) >> 20));
 
+	/*
+	 * Allow 30-bit DMA for very limited Broadcom wifi chips on many
+	 * powerbooks.
+	 */
+	if (IS_ENABLED(CONFIG_PPC32))
+		arch_zone_dma_bits = 30;
+	else
+		arch_zone_dma_bits = 31;
+
 #ifdef CONFIG_ZONE_DMA
 	max_zone_pfns[ZONE_DMA]	= min(max_low_pfn,
-				      1UL << (ARCH_ZONE_DMA_BITS - PAGE_SHIFT));
+				      1UL << (arch_zone_dma_bits - PAGE_SHIFT));
 #endif
 	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
 #ifdef CONFIG_HIGHMEM
diff --git a/arch/s390/include/asm/page.h b/arch/s390/include/asm/page.h
index 823578c6b9e2..a4d38092530a 100644
--- a/arch/s390/include/asm/page.h
+++ b/arch/s390/include/asm/page.h
@@ -177,8 +177,6 @@ static inline int devmem_is_allowed(unsigned long pfn)
 #define VM_DATA_DEFAULT_FLAGS	(VM_READ | VM_WRITE | \
 				 VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)
 
-#define ARCH_ZONE_DMA_BITS	31
-
 #include <asm-generic/memory_model.h>
 #include <asm-generic/getorder.h>
 
diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index 20340a03ad90..07d93955d3e4 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -118,6 +118,7 @@ void __init paging_init(void)
 
 	sparse_memory_present_with_active_regions(MAX_NUMNODES);
 	sparse_init();
+	arch_zone_dma_bits = 31;
 	memset(max_zone_pfns, 0, sizeof(max_zone_pfns));
 	max_zone_pfns[ZONE_DMA] = PFN_DOWN(MAX_DMA_ADDRESS);
 	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
index adf993a3bd58..a1b353b77858 100644
--- a/include/linux/dma-direct.h
+++ b/include/linux/dma-direct.h
@@ -5,6 +5,8 @@
 #include <linux/dma-mapping.h>
 #include <linux/mem_encrypt.h>
 
+extern unsigned int arch_zone_dma_bits;
+
 #ifdef CONFIG_ARCH_HAS_PHYS_TO_DMA
 #include <asm/dma-direct.h>
 #else
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 59bdceea3737..40dfc9b4ee4c 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -19,9 +19,7 @@
  * Most architectures use ZONE_DMA for the first 16 Megabytes, but
  * some use it for entirely different regions:
  */
-#ifndef ARCH_ZONE_DMA_BITS
-#define ARCH_ZONE_DMA_BITS 24
-#endif
+unsigned int arch_zone_dma_bits __ro_after_init = 24;
 
 static void report_addr(struct device *dev, dma_addr_t dma_addr, size_t size)
 {
@@ -72,7 +70,7 @@ static gfp_t __dma_direct_optimal_gfp_mask(struct device *dev, u64 dma_mask,
 	 * Note that GFP_DMA32 and GFP_DMA are no ops without the corresponding
 	 * zones.
 	 */
-	if (*phys_mask <= DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
+	if (*phys_mask <= DMA_BIT_MASK(arch_zone_dma_bits))
 		return GFP_DMA;
 	if (*phys_mask <= DMA_BIT_MASK(32))
 		return GFP_DMA32;
@@ -387,7 +385,7 @@ int dma_direct_supported(struct device *dev, u64 mask)
 	u64 min_mask;
 
 	if (IS_ENABLED(CONFIG_ZONE_DMA))
-		min_mask = DMA_BIT_MASK(ARCH_ZONE_DMA_BITS);
+		min_mask = DMA_BIT_MASK(arch_zone_dma_bits);
 	else
 		min_mask = DMA_BIT_MASK(32);
 
-- 
2.22.0