linux-kernel - [PATCH v2 01/11] asm-generic: add dma_zone

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Date:   Tue, 20 Aug 2019 16:58:09 +0200
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     catalin.marinas@....com, hch@....de, wahrenst@....net,
        marc.zyngier@....com, robh+dt@...nel.org,
        Robin Murphy <robin.murphy@....com>,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-arch@...r.kernel.org, iommu@...ts.linux-foundation.org,
        linux-mm@...ck.org, linux-riscv@...ts.infradead.org,
        Arnd Bergmann <arnd@...db.de>
Cc:     phill@...pberryi.org, f.fainelli@...il.com, will@...nel.org,
        nsaenzjulienne@...e.de, linux-kernel@...r.kernel.org,
        eric@...olt.net, mbrugger@...e.com,
        linux-rpi-kernel@...ts.infradead.org, akpm@...ux-foundation.org,
        frowand.list@...il.com, m.szyprowski@...sung.com
Subject: [PATCH v2 01/11] asm-generic: add dma_zone_size

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@...e.de>
---

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