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Subject[PATCH 7/7] arc: use the generic remapping allocator for coherent DMA allocations
Date
Replace the code that sets up uncached PTEs with the generic vmap based
remapping code. It also provides an atomic pool for allocations from
non-blocking context, which we not properly supported by the existing
arc code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
arch/arc/Kconfig | 2 ++
arch/arc/mm/dma.c | 62 ++++++++---------------------------------------
2 files changed, 12 insertions(+), 52 deletions(-)

diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 23e063df5d2c..cdad7d30ff1d 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -10,6 +10,7 @@ config ARC
def_bool y
select ARC_TIMERS
select ARCH_HAS_DMA_COHERENT_TO_PFN
+ select ARCH_HAS_DMA_PREP_COHERENT
select ARCH_HAS_PTE_SPECIAL
select ARCH_HAS_SETUP_DMA_OPS
select ARCH_HAS_SYNC_DMA_FOR_CPU
@@ -19,6 +20,7 @@ config ARC
select BUILDTIME_EXTABLE_SORT
select CLONE_BACKWARDS
select COMMON_CLK
+ select DMA_DIRECT_REMAP
select GENERIC_ATOMIC64 if !ISA_ARCV2 || !(ARC_HAS_LL64 && ARC_HAS_LLSC)
select GENERIC_CLOCKEVENTS
select GENERIC_FIND_FIRST_BIT
diff --git a/arch/arc/mm/dma.c b/arch/arc/mm/dma.c
index 9832928f896d..0fa850709fac 100644
--- a/arch/arc/mm/dma.c
+++ b/arch/arc/mm/dma.c
@@ -11,46 +11,15 @@
#include <asm/cacheflush.h>

/*
- * ARCH specific callbacks for generic noncoherent DMA ops (dma/noncoherent.c)
+ * ARCH specific callbacks for generic noncoherent DMA ops
* - hardware IOC not available (or "dma-coherent" not set for device in DT)
* - But still handle both coherent and non-coherent requests from caller
*
* For DMA coherent hardware (IOC) generic code suffices
*/
-void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
- gfp_t gfp, unsigned long attrs)
-{
- unsigned long order = get_order(size);
- struct page *page;
- phys_addr_t paddr;
- void *kvaddr;
-
- /*
- * __GFP_HIGHMEM flag is cleared by upper layer functions
- * (in include/linux/dma-mapping.h) so we should never get a
- * __GFP_HIGHMEM here.
- */
- BUG_ON(gfp & __GFP_HIGHMEM);
-
- page = alloc_pages(gfp | __GFP_ZERO, order);
- if (!page)
- return NULL;
-
- /* This is linear addr (0x8000_0000 based) */
- paddr = page_to_phys(page);
-
- *dma_handle = paddr;
-
- /*
- * A coherent buffer needs MMU mapping to enforce non-cachability.
- * kvaddr is kernel Virtual address (0x7000_0000 based).
- */
- kvaddr = ioremap_nocache(paddr, size);
- if (kvaddr == NULL) {
- __free_pages(page, order);
- return NULL;
- }

+void arch_dma_prep_coherent(struct page *page, size_t size)
+{
/*
* Evict any existing L1 and/or L2 lines for the backing page
* in case it was used earlier as a normal "cached" page.
@@ -61,24 +30,7 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
* Currently flush_cache_vmap nukes the L1 cache completely which
* will be optimized as a separate commit
*/
- dma_cache_wback_inv(paddr, size);
- return kvaddr;
-}
-
-void arch_dma_free(struct device *dev, size_t size, void *vaddr,
- dma_addr_t dma_handle, unsigned long attrs)
-{
- phys_addr_t paddr = dma_handle;
- struct page *page = virt_to_page(paddr);
-
- iounmap((void __force __iomem *)vaddr);
- __free_pages(page, get_order(size));
-}
-
-long arch_dma_coherent_to_pfn(struct device *dev, void *cpu_addr,
- dma_addr_t dma_addr)
-{
- return __phys_to_pfn(dma_addr);
+ dma_cache_wback_inv(page_to_phys(page), size);
}

/*
@@ -155,3 +107,9 @@ 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);
--
2.20.1
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