linux-kernel - [PATCH 16/31] s390: handle page-less SG entries

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Date:	Wed, 12 Aug 2015 09:05:35 +0200
From:	Christoph Hellwig <hch@....de>
To:	torvalds@...ux-foundation.org, axboe@...nel.dk
Cc:	dan.j.williams@...el.com, vgupta@...opsys.com,
	hskinnemoen@...il.com, egtvedt@...fundet.no, realmz6@...il.com,
	dhowells@...hat.com, monstr@...str.eu, x86@...nel.org,
	dwmw2@...radead.org, alex.williamson@...hat.com,
	grundler@...isc-linux.org, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org, linux-alpha@...r.kernel.org,
	linux-ia64@...r.kernel.org, linux-metag@...r.kernel.org,
	linux-mips@...ux-mips.org, linux-parisc@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
	sparclinux@...r.kernel.org, linux-xtensa@...ux-xtensa.org,
	linux-nvdimm@...1.01.org, linux-media@...r.kernel.org
Subject: [PATCH 16/31] s390: handle page-less SG entries

Use sg_phys() instead of page_to_phys(sg_page(sg)) so that we don't
require a page structure for all DMA memory.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 arch/s390/pci/pci_dma.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/arch/s390/pci/pci_dma.c b/arch/s390/pci/pci_dma.c
index 6fd8d58..aae5a47 100644
--- a/arch/s390/pci/pci_dma.c
+++ b/arch/s390/pci/pci_dma.c
@@ -272,14 +272,13 @@ int dma_set_mask(struct device *dev, u64 mask)
 }
 EXPORT_SYMBOL_GPL(dma_set_mask);
 
-static dma_addr_t s390_dma_map_pages(struct device *dev, struct page *page,
-				     unsigned long offset, size_t size,
+static dma_addr_t s390_dma_map_phys(struct device *dev, unsigned long pa,
+				     size_t size,
 				     enum dma_data_direction direction,
 				     struct dma_attrs *attrs)
 {
 	struct zpci_dev *zdev = get_zdev(to_pci_dev(dev));
 	unsigned long nr_pages, iommu_page_index;
-	unsigned long pa = page_to_phys(page) + offset;
 	int flags = ZPCI_PTE_VALID;
 	dma_addr_t dma_addr;
 
@@ -301,7 +300,7 @@ static dma_addr_t s390_dma_map_pages(struct device *dev, struct page *page,
 
 	if (!dma_update_trans(zdev, pa, dma_addr, size, flags)) {
 		atomic64_add(nr_pages, &zdev->mapped_pages);
-		return dma_addr + (offset & ~PAGE_MASK);
+		return dma_addr + (pa & ~PAGE_MASK);
 	}
 
 out_free:
@@ -312,6 +311,16 @@ out_err:
 	return DMA_ERROR_CODE;
 }
 
+static dma_addr_t s390_dma_map_pages(struct device *dev, struct page *page,
+				     unsigned long offset, size_t size,
+				     enum dma_data_direction direction,
+				     struct dma_attrs *attrs)
+{
+	unsigned long pa = page_to_phys(page) + offset;
+
+	return s390_dma_map_phys(dev, pa, size, direction, attrs);
+}
+
 static void s390_dma_unmap_pages(struct device *dev, dma_addr_t dma_addr,
 				 size_t size, enum dma_data_direction direction,
 				 struct dma_attrs *attrs)
@@ -384,8 +393,7 @@ static int s390_dma_map_sg(struct device *dev, struct scatterlist *sg,
 	int i;
 
 	for_each_sg(sg, s, nr_elements, i) {
-		struct page *page = sg_page(s);
-		s->dma_address = s390_dma_map_pages(dev, page, s->offset,
+		s->dma_address = s390_dma_map_phys(dev, sg_phys(s),
 						    s->length, dir, NULL);
 		if (!dma_mapping_error(dev, s->dma_address)) {
 			s->dma_length = s->length;
-- 
1.9.1

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