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Subject[PATCH 50/67] swiotlb: refactor coherent buffer allocation
Date
Factor out a new swiotlb_alloc_buffer helper that allocates DMA coherent
memory from the swiotlb bounce buffer.

This allows to simplify the swiotlb_alloc implemenation that uses
dma_direct_alloc to try to allocate a reachable buffer first.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
lib/swiotlb.c | 100 ++++++++++++++++++++++++++++++----------------------------
1 file changed, 51 insertions(+), 49 deletions(-)

diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index adb4dd0091fa..905eea6353a3 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -709,67 +709,69 @@ void swiotlb_tbl_sync_single(struct device *hwdev, phys_addr_t tlb_addr,
}
EXPORT_SYMBOL_GPL(swiotlb_tbl_sync_single);

+static void *
+swiotlb_alloc_buffer(struct device *dev, size_t size, dma_addr_t *dma_handle)
+{
+ phys_addr_t phys_addr;
+
+ if (swiotlb_force == SWIOTLB_NO_FORCE)
+ goto out_warn;
+
+ phys_addr = swiotlb_tbl_map_single(dev,
+ swiotlb_phys_to_dma(dev, io_tlb_start),
+ 0, size, DMA_FROM_DEVICE, 0);
+ if (phys_addr == SWIOTLB_MAP_ERROR)
+ goto out_warn;
+
+ *dma_handle = swiotlb_phys_to_dma(dev, phys_addr);
+
+ /* Confirm address can be DMA'd by device */
+ if (*dma_handle + size - 1 > dev->coherent_dma_mask)
+ goto out_unmap;
+
+ memset(phys_to_virt(phys_addr), 0, size);
+ return phys_to_virt(phys_addr);
+
+out_unmap:
+ dev_warn(dev, "hwdev DMA mask = 0x%016Lx, dev_addr = 0x%016Lx\n",
+ (unsigned long long)dev->coherent_dma_mask,
+ (unsigned long long)*dma_handle);
+
+ /*
+ * DMA_TO_DEVICE to avoid memcpy in unmap_single.
+ * DMA_ATTR_SKIP_CPU_SYNC is optional.
+ */
+ swiotlb_tbl_unmap_single(dev, phys_addr, size, DMA_TO_DEVICE,
+ DMA_ATTR_SKIP_CPU_SYNC);
+out_warn:
+ dev_warn(dev,
+ "swiotlb: coherent allocation failed, size=%zu\n", size);
+ dump_stack();
+ return NULL;
+}
+
void *
swiotlb_alloc_coherent(struct device *hwdev, size_t size,
dma_addr_t *dma_handle, gfp_t flags)
{
- dma_addr_t dev_addr;
- void *ret;
int order = get_order(size);
+ void *ret;

ret = (void *)__get_free_pages(flags, order);
if (ret) {
- dev_addr = swiotlb_virt_to_bus(hwdev, ret);
- if (dev_addr + size - 1 > hwdev->coherent_dma_mask) {
- /*
- * The allocated memory isn't reachable by the device.
- */
- free_pages((unsigned long) ret, order);
- ret = NULL;
+ *dma_handle = swiotlb_virt_to_bus(hwdev, ret);
+ if (*dma_handle + size - 1 <= hwdev->coherent_dma_mask) {
+ memset(ret, 0, size);
+ return ret;
}
- }
- if (!ret) {
+
/*
- * We are either out of memory or the device can't DMA to
- * GFP_DMA memory; fall back on map_single(), which
- * will grab memory from the lowest available address range.
+ * The allocated memory isn't reachable by the device.
*/
- phys_addr_t paddr = map_single(hwdev, 0, size,
- DMA_FROM_DEVICE, 0);
- if (paddr == SWIOTLB_MAP_ERROR)
- goto err_warn;
-
- ret = phys_to_virt(paddr);
- dev_addr = swiotlb_phys_to_dma(hwdev, paddr);
-
- /* Confirm address can be DMA'd by device */
- if (dev_addr + size - 1 > hwdev->coherent_dma_mask) {
- printk("hwdev DMA mask = 0x%016Lx, dev_addr = 0x%016Lx\n",
- (unsigned long long)hwdev->coherent_dma_mask,
- (unsigned long long)dev_addr);
-
- /*
- * DMA_TO_DEVICE to avoid memcpy in unmap_single.
- * The DMA_ATTR_SKIP_CPU_SYNC is optional.
- */
- swiotlb_tbl_unmap_single(hwdev, paddr,
- size, DMA_TO_DEVICE,
- DMA_ATTR_SKIP_CPU_SYNC);
- goto err_warn;
- }
+ free_pages((unsigned long) ret, order);
}

- *dma_handle = dev_addr;
- memset(ret, 0, size);
-
- return ret;
-
-err_warn:
- pr_warn("swiotlb: coherent allocation failed for device %s size=%zu\n",
- dev_name(hwdev), size);
- dump_stack();
-
- return NULL;
+ return swiotlb_alloc_buffer(hwdev, size, dma_handle);
}
EXPORT_SYMBOL(swiotlb_alloc_coherent);

@@ -1105,7 +1107,7 @@ void *swiotlb_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,

vaddr = dma_direct_alloc(dev, size, dma_handle, gfp, attrs);
if (!vaddr)
- vaddr = swiotlb_alloc_coherent(dev, size, dma_handle, gfp);
+ vaddr = swiotlb_alloc_buffer(dev, size, dma_handle);
return vaddr;
}

--
2.14.2
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