[PATCH v6 1/7] dma: Take into account dma_pfn_offset

[Vladimir Murzin]

Even though dma-noop-ops assumes 1:1 memory mapping DMA memory range
can be different to RAM. For example, ARM STM32F4 MCU offers the
possibility to remap SDRAM from 0xc000_0000 to 0x0 to get CPU
performance boost, but DMA continue to see SDRAM at 0xc000_0000. This
difference in mapping is handled via device-tree "dma-range" property
which leads to dev->dma_pfn_offset is set nonzero. To handle such
cases take dma_pfn_offset into account.

Cc: Joerg Roedel <jroedel@xxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Reported-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxx>
Tested-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxx>
Tested-by: Andras Szemzo <sza@xxxxxx>
Tested-by: Alexandre TORGUE <alexandre.torgue@xxxxxx>
Reviewed-by: Robin Murphy <robin.murphy@xxxxxxx>
Signed-off-by: Vladimir Murzin <vladimir.murzin@xxxxxxx>
---
 lib/dma-noop.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/lib/dma-noop.c b/lib/dma-noop.c
index de26c8b..1f60c8a 100644
--- a/lib/dma-noop.c
+++ b/lib/dma-noop.c
@@ -7,6 +7,7 @@
 #include <linux/mm.h>
 #include <linux/dma-mapping.h>
 #include <linux/scatterlist.h>
+#include <linux/pfn.h>
 
 static void *dma_noop_alloc(struct device *dev, size_t size,
 			    dma_addr_t *dma_handle, gfp_t gfp,
@@ -16,7 +17,8 @@ static void *dma_noop_alloc(struct device *dev, size_t size,
 
 	ret = (void *)__get_free_pages(gfp, get_order(size));
 	if (ret)
-		*dma_handle = virt_to_phys(ret);
+		*dma_handle = virt_to_phys(ret) - PFN_PHYS(dev->dma_pfn_offset);
+
 	return ret;
 }
 
@@ -32,7 +34,7 @@ static dma_addr_t dma_noop_map_page(struct device *dev, struct page *page,
 				      enum dma_data_direction dir,
 				      unsigned long attrs)
 {
-	return page_to_phys(page) + offset;
+	return page_to_phys(page) + offset - PFN_PHYS(dev->dma_pfn_offset);
 }
 
 static int dma_noop_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
@@ -43,11 +45,12 @@ static int dma_noop_map_sg(struct device *dev, struct scatterlist *sgl, int nent
 	struct scatterlist *sg;
 
 	for_each_sg(sgl, sg, nents, i) {
+		dma_addr_t offset = PFN_PHYS(dev->dma_pfn_offset);
 		void *va;
 
 		BUG_ON(!sg_page(sg));
 		va = sg_virt(sg);
-		sg_dma_address(sg) = (dma_addr_t)virt_to_phys(va);
+		sg_dma_address(sg) = (dma_addr_t)virt_to_phys(va) - offset;
 		sg_dma_len(sg) = sg->length;
 	}
 
-- 
2.0.0