[OpenRISC] [PATCH 04/10] arm: implement DMA_ATTR_NON_CONSISTENT

[Christoph Hellwig <hch@lst.de>]

For the iommu ops we can just use the implementaton for DMA coherent
devices.  For the regular ops we need mix and match a bit so that
we either use the CMA allocator without remapping, but with a special
error handling case for highmem pages, or the simple allocator.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/arm/mm/dma-mapping.c | 49 ++++++++++++++++++++++++++++-----------
 1 file changed, 35 insertions(+), 14 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 2cfb17bad1e6..b3b66b41c450 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -49,6 +49,7 @@ struct arm_dma_alloc_args {
 	const void *caller;
 	bool want_vaddr;
 	int coherent_flag;
+	bool nonconsistent_flag;
 };
 
 struct arm_dma_free_args {
@@ -57,6 +58,7 @@ struct arm_dma_free_args {
 	void *cpu_addr;
 	struct page *page;
 	bool want_vaddr;
+	bool nonconsistent_flag;
 };
 
 #define NORMAL	    0
@@ -348,7 +350,8 @@ static void __dma_free_buffer(struct page *page, size_t size)
 static void *__alloc_from_contiguous(struct device *dev, size_t size,
 				     pgprot_t prot, struct page **ret_page,
 				     const void *caller, bool want_vaddr,
-				     int coherent_flag, gfp_t gfp);
+				     int coherent_flag, bool nonconsistent_flag,
+				     gfp_t gfp);
 
 static void *__alloc_remap_buffer(struct device *dev, size_t size, gfp_t gfp,
 				 pgprot_t prot, struct page **ret_page,
@@ -405,7 +408,7 @@ static int __init atomic_pool_init(void)
 	if (dev_get_cma_area(NULL))
 		ptr = __alloc_from_contiguous(NULL, atomic_pool_size, prot,
 				      &page, atomic_pool_init, true, NORMAL,
-				      GFP_KERNEL);
+				      false, GFP_KERNEL);
 	else
 		ptr = __alloc_remap_buffer(NULL, atomic_pool_size, gfp, prot,
 					   &page, atomic_pool_init, true);
@@ -579,7 +582,8 @@ static int __free_from_pool(void *start, size_t size)
 static void *__alloc_from_contiguous(struct device *dev, size_t size,
 				     pgprot_t prot, struct page **ret_page,
 				     const void *caller, bool want_vaddr,
-				     int coherent_flag, gfp_t gfp)
+				     int coherent_flag, bool nonconsistent_flag,
+				     gfp_t gfp)
 {
 	unsigned long order = get_order(size);
 	size_t count = size >> PAGE_SHIFT;
@@ -595,12 +599,16 @@ static void *__alloc_from_contiguous(struct device *dev, size_t size,
 	if (!want_vaddr)
 		goto out;
 
+	if (nonconsistent_flag) {
+		if (PageHighMem(page))
+			goto fail;
+		goto out;
+	}
+
 	if (PageHighMem(page)) {
 		ptr = __dma_alloc_remap(page, size, GFP_KERNEL, prot, caller);
-		if (!ptr) {
-			dma_release_from_contiguous(dev, page, count);
-			return NULL;
-		}
+		if (!ptr)
+			goto fail;
 	} else {
 		__dma_remap(page, size, prot);
 		ptr = page_address(page);
@@ -609,12 +617,15 @@ static void *__alloc_from_contiguous(struct device *dev, size_t size,
  out:
 	*ret_page = page;
 	return ptr;
+ fail:
+	dma_release_from_contiguous(dev, page, count);
+	return NULL;
 }
 
 static void __free_from_contiguous(struct device *dev, struct page *page,
-				   void *cpu_addr, size_t size, bool want_vaddr)
+				   void *cpu_addr, size_t size, bool remapped)
 {
-	if (want_vaddr) {
+	if (remapped) {
 		if (PageHighMem(page))
 			__dma_free_remap(cpu_addr, size);
 		else
@@ -635,7 +646,11 @@ static void *__alloc_simple_buffer(struct device *dev, size_t size, gfp_t gfp,
 				   struct page **ret_page)
 {
 	struct page *page;
-	/* __alloc_simple_buffer is only called when the device is coherent */
+	/*
+	 * __alloc_simple_buffer is only called when the device is coherent,
+	 * or if the caller explicitly asked for an allocation that is not
+	 * consistent.
+	 */
 	page = __dma_alloc_buffer(dev, size, gfp, COHERENT);
 	if (!page)
 		return NULL;
@@ -667,13 +682,15 @@ static void *cma_allocator_alloc(struct arm_dma_alloc_args *args,
 	return __alloc_from_contiguous(args->dev, args->size, args->prot,
 				       ret_page, args->caller,
 				       args->want_vaddr, args->coherent_flag,
+				       args->nonconsistent_flag,
 				       args->gfp);
 }
 
 static void cma_allocator_free(struct arm_dma_free_args *args)
 {
 	__free_from_contiguous(args->dev, args->page, args->cpu_addr,
-			       args->size, args->want_vaddr);
+			       args->size,
+			       args->want_vaddr || args->nonconsistent_flag);
 }
 
 static struct arm_dma_allocator cma_allocator = {
@@ -735,6 +752,7 @@ static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
 		.caller = caller,
 		.want_vaddr = ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) == 0),
 		.coherent_flag = is_coherent ? COHERENT : NORMAL,
+		.nonconsistent_flag = (attrs & DMA_ATTR_NON_CONSISTENT),
 	};
 
 #ifdef CONFIG_DMA_API_DEBUG
@@ -773,7 +791,7 @@ static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
 
 	if (cma)
 		buf->allocator = &cma_allocator;
-	else if (is_coherent)
+	else if (is_coherent || (attrs & DMA_ATTR_NON_CONSISTENT))
 		buf->allocator = &simple_allocator;
 	else if (allowblock)
 		buf->allocator = &remap_allocator;
@@ -874,6 +892,7 @@ static void __arm_dma_free(struct device *dev, size_t size, void *cpu_addr,
 		.cpu_addr = cpu_addr,
 		.page = page,
 		.want_vaddr = ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) == 0),
+		.nonconsistent_flag = (attrs & DMA_ATTR_NON_CONSISTENT),
 	};
 
 	buf = arm_dma_buffer_find(cpu_addr);
@@ -1562,7 +1581,8 @@ static void *__arm_iommu_alloc_attrs(struct device *dev, size_t size,
 static void *arm_iommu_alloc_attrs(struct device *dev, size_t size,
 	    dma_addr_t *handle, gfp_t gfp, unsigned long attrs)
 {
-	return __arm_iommu_alloc_attrs(dev, size, handle, gfp, attrs, NORMAL);
+	return __arm_iommu_alloc_attrs(dev, size, handle, gfp, attrs,
+			(attrs & DMA_ATTR_NON_CONSISTENT) ? COHERENT : NORMAL);
 }
 
 static void *arm_coherent_iommu_alloc_attrs(struct device *dev, size_t size,
@@ -1650,7 +1670,8 @@ void __arm_iommu_free_attrs(struct device *dev, size_t size, void *cpu_addr,
 void arm_iommu_free_attrs(struct device *dev, size_t size,
 		    void *cpu_addr, dma_addr_t handle, unsigned long attrs)
 {
-	__arm_iommu_free_attrs(dev, size, cpu_addr, handle, attrs, NORMAL);
+	__arm_iommu_free_attrs(dev, size, cpu_addr, handle, attrs,
+			(attrs & DMA_ATTR_NON_CONSISTENT) ? COHERENT : NORMAL);
 }
 
 void arm_coherent_iommu_free_attrs(struct device *dev, size_t size,
-- 
2.19.2