dma-mapping: make dma_atomic_pool_init self-contained

The memory allocated for the atomic pool needs to have the same
mapping attributes that we use for remapping, so use
pgprot_dmacoherent instead of open coding it.  Also deduct a
suitable zone to allocate the memory from based on the presence
of the DMA zones.
Signed-off-by: Christoph Hellwig <hch@lst.de>

arch/arc/mm/dma.c

@@ -104,9 +104,3 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
 	dev_info(dev, "use %sncoherent DMA ops\n",
 		 dev->dma_coherent ? "" : "non");
 }
-
-static int __init atomic_pool_init(void)
-{
-	return dma_atomic_pool_init(GFP_KERNEL, pgprot_noncached(PAGE_KERNEL));
-}
-postcore_initcall(atomic_pool_init);

arch/arm64/mm/dma-mapping.c

@@ -28,12 +28,6 @@ void arch_dma_prep_coherent(struct page *page, size_t size)
 	__dma_flush_area(page_address(page), size);
 }
 
-static int __init arm64_dma_init(void)
-{
-	return dma_atomic_pool_init(GFP_DMA32, __pgprot(PROT_NORMAL_NC));
-}
-arch_initcall(arm64_dma_init);
-
 #ifdef CONFIG_IOMMU_DMA
 void arch_teardown_dma_ops(struct device *dev)
 {

arch/csky/mm/dma-mapping.c

@@ -14,12 +14,6 @@
 #include <linux/version.h>
 #include <asm/cache.h>
 
-static int __init atomic_pool_init(void)
-{
-	return dma_atomic_pool_init(GFP_KERNEL, pgprot_noncached(PAGE_KERNEL));
-}
-postcore_initcall(atomic_pool_init);
-
 void arch_dma_prep_coherent(struct page *page, size_t size)
 {
 	if (PageHighMem(page)) {

arch/nds32/kernel/dma.c

@@ -80,9 +80,3 @@ void arch_dma_prep_coherent(struct page *page, size_t size)
 {
 	cache_op(page_to_phys(page), size, cpu_dma_wbinval_range);
 }
-
-static int __init atomic_pool_init(void)
-{
-	return dma_atomic_pool_init(GFP_KERNEL, pgprot_noncached(PAGE_KERNEL));
-}
-postcore_initcall(atomic_pool_init);

include/linux/dma-mapping.h

@@ -624,7 +624,6 @@ void *dma_common_pages_remap(struct page **pages, size_t size,
 			const void *caller);
 void dma_common_free_remap(void *cpu_addr, size_t size, unsigned long vm_flags);
 
-int __init dma_atomic_pool_init(gfp_t gfp, pgprot_t prot);
 bool dma_in_atomic_pool(void *start, size_t size);
 void *dma_alloc_from_pool(size_t size, struct page **ret_page, gfp_t flags);
 bool dma_free_from_pool(void *start, size_t size);

kernel/dma/remap.c

@@ -105,7 +105,16 @@ static int __init early_coherent_pool(char *p)
 }
 early_param("coherent_pool", early_coherent_pool);
 
-int __init dma_atomic_pool_init(gfp_t gfp, pgprot_t prot)
+static gfp_t dma_atomic_pool_gfp(void)
+{
+	if (IS_ENABLED(CONFIG_ZONE_DMA))
+		return GFP_DMA;
+	if (IS_ENABLED(CONFIG_ZONE_DMA32))
+		return GFP_DMA32;
+	return GFP_KERNEL;
+}
+
+static int __init dma_atomic_pool_init(void)
 {
 	unsigned int pool_size_order = get_order(atomic_pool_size);
 	unsigned long nr_pages = atomic_pool_size >> PAGE_SHIFT;
@@ -117,7 +126,7 @@ int __init dma_atomic_pool_init(gfp_t gfp, pgprot_t prot)
 		page = dma_alloc_from_contiguous(NULL, nr_pages,
 						 pool_size_order, false);
 	else
-		page = alloc_pages(gfp, pool_size_order);
+		page = alloc_pages(dma_atomic_pool_gfp(), pool_size_order);
 	if (!page)
 		goto out;
 
@@ -128,7 +137,8 @@ int __init dma_atomic_pool_init(gfp_t gfp, pgprot_t prot)
 		goto free_page;
 
 	addr = dma_common_contiguous_remap(page, atomic_pool_size, VM_USERMAP,
-					   prot, __builtin_return_address(0));
+					   pgprot_dmacoherent(PAGE_KERNEL),
+					   __builtin_return_address(0));
 	if (!addr)
 		goto destroy_genpool;
 
@@ -155,6 +165,7 @@ int __init dma_atomic_pool_init(gfp_t gfp, pgprot_t prot)
 		atomic_pool_size / 1024);
 	return -ENOMEM;
 }
+postcore_initcall(dma_atomic_pool_init);
 
 bool dma_in_atomic_pool(void *start, size_t size)
 {