[POWERPC] Use 4kB iommu pages even on 64kB-page systems

The 10Gigabit ethernet device drivers appear to be able to chew
up all 256MB of TCE mappings on pSeries systems, as evidenced by
numerous error messages:

 iommu_alloc failed, tbl c0000000010d5c48 vaddr c0000000d875eff0 npages 1

Some experimentation indicates that this is essentially because
one 1500 byte ethernet MTU gets mapped as a 64K DMA region when
the large 64K pages are enabled. Thus, it doesn't take much to
exhaust all of the available DMA mappings for a high-speed card.

This patch changes the iommu allocator to work with its own
unique, distinct page size. Although the patch is long, its
actually quite simple: it just #defines a distinct IOMMU_PAGE_SIZE
and then uses this in all the places that matter.

As a side effect, it also dramatically improves network performance
on platforms with H-calls on iommu translation inserts/removes (since
we no longer call it 16 times for a 1500 bytes packet when the iommu HW
is still 4k).

In the future, we might want to make the IOMMU_PAGE_SIZE a variable
in the iommu_table instance, thus allowing support for different HW
page sizes in the iommu itself.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

2 files changed, 47 insertions, 34 deletions

diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index f88a2a675d9..ba6b7256084 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -47,6 +47,17 @@ static int novmerge = 0;
 static int novmerge = 1;
 #endif
 
+static inline unsigned long iommu_num_pages(unsigned long vaddr,
+					    unsigned long slen)
+{
+	unsigned long npages;
+
+	npages = IOMMU_PAGE_ALIGN(vaddr + slen) - (vaddr & IOMMU_PAGE_MASK);
+	npages >>= IOMMU_PAGE_SHIFT;
+
+	return npages;
+}
+
 static int __init setup_iommu(char *str)
 {
 	if (!strcmp(str, "novmerge"))
@@ -178,10 +189,10 @@ static dma_addr_t iommu_alloc(struct iommu_table *tbl, void *page,
 	}
 
 	entry += tbl->it_offset;	/* Offset into real TCE table */
-	ret = entry << PAGE_SHIFT;	/* Set the return dma address */
+	ret = entry << IOMMU_PAGE_SHIFT;	/* Set the return dma address */
 
 	/* Put the TCEs in the HW table */
-	ppc_md.tce_build(tbl, entry, npages, (unsigned long)page & PAGE_MASK,
+	ppc_md.tce_build(tbl, entry, npages, (unsigned long)page & IOMMU_PAGE_MASK,
 			 direction);
 
 
@@ -203,7 +214,7 @@ static void __iommu_free(struct iommu_table *tbl, dma_addr_t dma_addr,
 	unsigned long entry, free_entry;
 	unsigned long i;
 
-	entry = dma_addr >> PAGE_SHIFT;
+	entry = dma_addr >> IOMMU_PAGE_SHIFT;
 	free_entry = entry - tbl->it_offset;
 
 	if (((free_entry + npages) > tbl->it_size) ||
@@ -270,7 +281,7 @@ int iommu_map_sg(struct device *dev, struct iommu_table *tbl,
 	/* Init first segment length for backout at failure */
 	outs->dma_length = 0;
 
-	DBG("mapping %d elements:\n", nelems);
+	DBG("sg mapping %d elements:\n", nelems);
 
 	spin_lock_irqsave(&(tbl->it_lock), flags);
 
@@ -285,9 +296,8 @@ int iommu_map_sg(struct device *dev, struct iommu_table *tbl,
 		}
 		/* Allocate iommu entries for that segment */
 		vaddr = (unsigned long)page_address(s->page) + s->offset;
-		npages = PAGE_ALIGN(vaddr + slen) - (vaddr & PAGE_MASK);
-		npages >>= PAGE_SHIFT;
-		entry = iommu_range_alloc(tbl, npages, &handle, mask >> PAGE_SHIFT, 0);
+		npages = iommu_num_pages(vaddr, slen);
+		entry = iommu_range_alloc(tbl, npages, &handle, mask >> IOMMU_PAGE_SHIFT, 0);
 
 		DBG("  - vaddr: %lx, size: %lx\n", vaddr, slen);
 
@@ -301,14 +311,14 @@ int iommu_map_sg(struct device *dev, struct iommu_table *tbl,
 
 		/* Convert entry to a dma_addr_t */
 		entry += tbl->it_offset;
-		dma_addr = entry << PAGE_SHIFT;
-		dma_addr |= s->offset;
+		dma_addr = entry << IOMMU_PAGE_SHIFT;
+		dma_addr |= (s->offset & ~IOMMU_PAGE_MASK);
 
-		DBG("  - %lx pages, entry: %lx, dma_addr: %lx\n",
+		DBG("  - %lu pages, entry: %lx, dma_addr: %lx\n",
 			    npages, entry, dma_addr);
 
 		/* Insert into HW table */
-		ppc_md.tce_build(tbl, entry, npages, vaddr & PAGE_MASK, direction);
+		ppc_md.tce_build(tbl, entry, npages, vaddr & IOMMU_PAGE_MASK, direction);
 
 		/* If we are in an open segment, try merging */
 		if (segstart != s) {
@@ -323,7 +333,7 @@ int iommu_map_sg(struct device *dev, struct iommu_table *tbl,
 				DBG("    can't merge, new segment.\n");
 			} else {
 				outs->dma_length += s->length;
-				DBG("    merged, new len: %lx\n", outs->dma_length);
+				DBG("    merged, new len: %ux\n", outs->dma_length);
 			}
 		}
 
@@ -367,9 +377,8 @@ int iommu_map_sg(struct device *dev, struct iommu_table *tbl,
 		if (s->dma_length != 0) {
 			unsigned long vaddr, npages;
 
-			vaddr = s->dma_address & PAGE_MASK;
-			npages = (PAGE_ALIGN(s->dma_address + s->dma_length) - vaddr)
-				>> PAGE_SHIFT;
+			vaddr = s->dma_address & IOMMU_PAGE_MASK;
+			npages = iommu_num_pages(s->dma_address, s->dma_length);
 			__iommu_free(tbl, vaddr, npages);
 			s->dma_address = DMA_ERROR_CODE;
 			s->dma_length = 0;
@@ -398,8 +407,7 @@ void iommu_unmap_sg(struct iommu_table *tbl, struct scatterlist *sglist,
 
 		if (sglist->dma_length == 0)
 			break;
-		npages = (PAGE_ALIGN(dma_handle + sglist->dma_length)
-			  - (dma_handle & PAGE_MASK)) >> PAGE_SHIFT;
+		npages = iommu_num_pages(dma_handle,sglist->dma_length);
 		__iommu_free(tbl, dma_handle, npages);
 		sglist++;
 	}
@@ -532,12 +540,11 @@ dma_addr_t iommu_map_single(struct iommu_table *tbl, void *vaddr,
 	BUG_ON(direction == DMA_NONE);
 
 	uaddr = (unsigned long)vaddr;
-	npages = PAGE_ALIGN(uaddr + size) - (uaddr & PAGE_MASK);
-	npages >>= PAGE_SHIFT;
+	npages = iommu_num_pages(uaddr, size);
 
 	if (tbl) {
 		dma_handle = iommu_alloc(tbl, vaddr, npages, direction,
-					 mask >> PAGE_SHIFT, 0);
+					 mask >> IOMMU_PAGE_SHIFT, 0);
 		if (dma_handle == DMA_ERROR_CODE) {
 			if (printk_ratelimit())  {
 				printk(KERN_INFO "iommu_alloc failed, "
@@ -545,7 +552,7 @@ dma_addr_t iommu_map_single(struct iommu_table *tbl, void *vaddr,
 						tbl, vaddr, npages);
 			}
 		} else
-			dma_handle |= (uaddr & ~PAGE_MASK);
+			dma_handle |= (uaddr & ~IOMMU_PAGE_MASK);
 	}
 
 	return dma_handle;
@@ -554,11 +561,14 @@ dma_addr_t iommu_map_single(struct iommu_table *tbl, void *vaddr,
 void iommu_unmap_single(struct iommu_table *tbl, dma_addr_t dma_handle,
 		size_t size, enum dma_data_direction direction)
 {
+	unsigned int npages;
+
 	BUG_ON(direction == DMA_NONE);
 
-	if (tbl)
-		iommu_free(tbl, dma_handle, (PAGE_ALIGN(dma_handle + size) -
-					(dma_handle & PAGE_MASK)) >> PAGE_SHIFT);
+	if (tbl) {
+		npages = iommu_num_pages(dma_handle, size);
+		iommu_free(tbl, dma_handle, npages);
+	}
 }
 
 /* Allocates a contiguous real buffer and creates mappings over it.
@@ -570,11 +580,11 @@ void *iommu_alloc_coherent(struct iommu_table *tbl, size_t size,
 {
 	void *ret = NULL;
 	dma_addr_t mapping;
-	unsigned int npages, order;
+	unsigned int order;
+	unsigned int nio_pages, io_order;
 	struct page *page;
 
 	size = PAGE_ALIGN(size);
-	npages = size >> PAGE_SHIFT;
 	order = get_order(size);
 
  	/*
@@ -598,8 +608,10 @@ void *iommu_alloc_coherent(struct iommu_table *tbl, size_t size,
 	memset(ret, 0, size);
 
 	/* Set up tces to cover the allocated range */
-	mapping = iommu_alloc(tbl, ret, npages, DMA_BIDIRECTIONAL,
-			      mask >> PAGE_SHIFT, order);
+	nio_pages = size >> IOMMU_PAGE_SHIFT;
+	io_order = get_iommu_order(size);
+	mapping = iommu_alloc(tbl, ret, nio_pages, DMA_BIDIRECTIONAL,
+			      mask >> IOMMU_PAGE_SHIFT, io_order);
 	if (mapping == DMA_ERROR_CODE) {
 		free_pages((unsigned long)ret, order);
 		return NULL;
@@ -611,12 +623,13 @@ void *iommu_alloc_coherent(struct iommu_table *tbl, size_t size,
 void iommu_free_coherent(struct iommu_table *tbl, size_t size,
 			 void *vaddr, dma_addr_t dma_handle)
 {
-	unsigned int npages;
-
 	if (tbl) {
+		unsigned int nio_pages;
+
+		size = PAGE_ALIGN(size);
+		nio_pages = size >> IOMMU_PAGE_SHIFT;
+		iommu_free(tbl, dma_handle, nio_pages);
 		size = PAGE_ALIGN(size);
-		npages = size >> PAGE_SHIFT;
-		iommu_free(tbl, dma_handle, npages);
 		free_pages((unsigned long)vaddr, get_order(size));
 	}
 }
diff --git a/arch/powerpc/kernel/vio.c b/arch/powerpc/kernel/vio.c
index cb87e71eec6..ed007878d1b 100644
--- a/arch/powerpc/kernel/vio.c
+++ b/arch/powerpc/kernel/vio.c
@@ -92,9 +92,9 @@ static struct iommu_table *vio_build_iommu_table(struct vio_dev *dev)
 				&tbl->it_index, &offset, &size);
 
 		/* TCE table size - measured in tce entries */
-		tbl->it_size = size >> PAGE_SHIFT;
+		tbl->it_size = size >> IOMMU_PAGE_SHIFT;
 		/* offset for VIO should always be 0 */
-		tbl->it_offset = offset >> PAGE_SHIFT;
+		tbl->it_offset = offset >> IOMMU_PAGE_SHIFT;
 		tbl->it_busno = 0;
 		tbl->it_type = TCE_VB;