[PATCH 10/22] swiotlb: refactor coherent buffer allocation

Christoph Hellwig
2018-01-10T08:14:11Z

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 | 122 +++++++++++++++++++++++++++++++---------------------------
1 file changed, 65 insertions(+), 57 deletions(-)

diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index 1a147f1354a1..bf2d19ee91c1 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -709,75 +709,79 @@ void swiotlb_tbl_sync_single(struct device *hwdev, phys_addr_t tlb_addr,
}
EXPORT_SYMBOL_GPL(swiotlb_tbl_sync_single);

-void *
-swiotlb_alloc_coherent(struct device *hwdev, size_t size,
- dma_addr_t *dma_handle, gfp_t flags)
+static inline bool dma_coherent_ok(struct device *dev, dma_addr_t addr,
+ size_t size)
{
- bool warn = !(flags & __GFP_NOWARN);
- dma_addr_t dev_addr;
- void *ret;
- int order = get_order(size);
- u64 dma_mask = DMA_BIT_MASK(32);
+ u64 mask = DMA_BIT_MASK(32);

- if (hwdev && hwdev->coherent_dma_mask)
- dma_mask = hwdev->coherent_dma_mask;
+ if (dev && dev->coherent_dma_mask)
+ mask = dev->coherent_dma_mask;
+ return addr + size - 1 <= mask;
+}

- ret = (void *)__get_free_pages(flags, order);
- if (ret) {
- dev_addr = swiotlb_virt_to_bus(hwdev, ret);
- if (dev_addr + size - 1 > dma_mask) {
- /*
- * The allocated memory isn't reachable by the device.
- */
- free_pages((unsigned long) ret, order);
- ret = NULL;
- }
- }
- 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.
- */
- phys_addr_t paddr = map_single(hwdev, 0, size, DMA_FROM_DEVICE,
- warn ? 0 : DMA_ATTR_NO_WARN);
- if (paddr == SWIOTLB_MAP_ERROR)
- goto err_warn;
+static void *
+swiotlb_alloc_buffer(struct device *dev, size_t size, dma_addr_t *dma_handle,
+ unsigned long attrs)
+{
+ phys_addr_t phys_addr;
+
+ if (swiotlb_force == SWIOTLB_NO_FORCE)
+ goto out_warn;

- ret = phys_to_virt(paddr);
- dev_addr = swiotlb_phys_to_dma(hwdev, paddr);
+ 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;

- /* Confirm address can be DMA'd by device */
- if (dev_addr + size - 1 > dma_mask) {
- printk("hwdev DMA mask = 0x%016Lx, dev_addr = 0x%016Lx\n",
- (unsigned long long)dma_mask,
- (unsigned long long)dev_addr);
+ *dma_handle = swiotlb_phys_to_dma(dev, phys_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;
- }
- }
+ if (dma_coherent_ok(dev, *dma_handle, size))
+ goto out_unmap;

- *dma_handle = dev_addr;
- memset(ret, 0, size);
+ memset(phys_to_virt(phys_addr), 0, size);
+ return phys_to_virt(phys_addr);

- return ret;
+out_unmap:
+ dev_warn(dev, "hwdev DMA mask = 0x%016Lx, dev_addr = 0x%016Lx\n",
+ (unsigned long long)(dev ? dev->coherent_dma_mask : 0),
+ (unsigned long long)*dma_handle);

-err_warn:
- if (warn && printk_ratelimit()) {
- pr_warn("swiotlb: coherent allocation failed for device %s size=%zu\n",
- dev_name(hwdev), size);
+ /*
+ * 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:
+ if ((attrs & DMA_ATTR_NO_WARN) && printk_ratelimit()) {
+ 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)
+{
+ int order = get_order(size);
+ unsigned long attrs = (flags & __GFP_NOWARN) ? DMA_ATTR_NO_WARN : 0;
+ void *ret;
+
+ ret = (void *)__get_free_pages(flags, order);
+ if (ret) {
+ *dma_handle = swiotlb_virt_to_bus(hwdev, ret);
+ if (dma_coherent_ok(hwdev, *dma_handle, size)) {
+ memset(ret, 0, size);
+ return ret;
+ }
+ }
+
+ return swiotlb_alloc_buffer(hwdev, size, dma_handle, attrs);
+}
EXPORT_SYMBOL(swiotlb_alloc_coherent);

static bool swiotlb_free_buffer(struct device *dev, size_t size,
@@ -1103,6 +1107,10 @@ void *swiotlb_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
{
void *vaddr;

+ /* temporary workaround: */
+ if (gfp & __GFP_NOWARN)
+ attrs |= DMA_ATTR_NO_WARN;
+
/*
* Don't print a warning when the first allocation attempt fails.
* swiotlb_alloc_coherent() will print a warning when the DMA memory
@@ -1112,7 +1120,7 @@ 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, attrs);
return vaddr;
}

--
2.14.2