[PATCH v2 01/11] asm-generic: add dma_zone_size

[Nicolas Saenz Julienne]

Some architectures have platform specific DMA addressing limitations.
This will allow for hardware description code to provide the constraints
in a generic manner, so as for arch code to properly setup it's memory
zones and DMA mask.

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

Changes in v2: None

 include/asm-generic/dma.h | 8 +++++++-
 mm/page_alloc.c           | 3 +++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/include/asm-generic/dma.h b/include/asm-generic/dma.h
index 43d0c8af8058..c2f39cdb64f6 100644
--- a/include/asm-generic/dma.h
+++ b/include/asm-generic/dma.h
@@ -8,7 +8,13 @@
  *
  * Some code relies on seeing MAX_DMA_ADDRESS though.
  */
-#define MAX_DMA_ADDRESS PAGE_OFFSET
+#define MAX_DMA_ADDRESS	 (PAGE_OFFSET + dma_zone_size)
+
+/*
+ * Some architectures may have platform specific DMA addressing constraints.
+ * Firmware can use this to fine tune the device's DMA memory zone.
+ */
+extern u64 dma_zone_size __ro_after_init;
 
 extern int request_dma(unsigned int dmanr, const char *device_id);
 extern void free_dma(unsigned int dmanr);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 272c6de1bf4e..b514afee5451 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -133,6 +133,9 @@ EXPORT_SYMBOL(_totalram_pages);
 unsigned long totalreserve_pages __read_mostly;
 unsigned long totalcma_pages __read_mostly;
 
+u64 dma_zone_size __ro_after_init;
+EXPORT_SYMBOL(dma_zone_size);
+
 int percpu_pagelist_fraction;
 gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK;
 #ifdef CONFIG_INIT_ON_ALLOC_DEFAULT_ON
-- 
2.22.0