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Subject[patch] pci_dma_sync_to_device

Hi,

following your suggestion this patch adds the missing
pci_dma_sync_to_device_{single,sg} call to sync streaming write buffers
after cpu modification. Like other pci dma calls it's a pci specific
wrapper plus corresponding generic function in asm-i386/dma-mapping.h.
Other platforms still need their individual implementations.

Patch below is against 2.6.0-test8. Testing was done using a modified
version of the vlsi_ir driver which calls pci_dma_to_device_single instead
of a private implementation.

I'm wondering whether it would be a good idea to add some BUG_ON there to
catch bad combinations with transfer direction. OTOH, on i386 the worst
to happen might be some unneeded flushes...

Martin

-----------------

--- linux-2.6.0-test8/include/asm-i386/dma-mapping.h Wed Oct 8 21:24:53 2003
+++ v2.6.0-test8-md/include/asm-i386/dma-mapping.h Tue Oct 21 10:56:45 2003
@@ -92,6 +92,20 @@
flush_write_buffers();
}

+static inline void
+dma_sync_to_device_single(struct device *dev, dma_addr_t dma_handle, size_t size,
+ enum dma_data_direction direction)
+{
+ flush_write_buffers();
+}
+
+static inline void
+dma_sync_to_device_sg(struct device *dev, struct scatterlist *sg, int nelems,
+ enum dma_data_direction direction)
+{
+ flush_write_buffers();
+}
+
static inline int
dma_supported(struct device *dev, u64 mask)
{
--- linux-2.6.0-test8/include/asm-generic/pci-dma-compat.h Wed Oct 8 21:24:02 2003
+++ v2.6.0-test8-md/include/asm-generic/pci-dma-compat.h Tue Oct 21 10:55:09 2003
@@ -84,4 +84,18 @@
dma_sync_sg(hwdev == NULL ? NULL : &hwdev->dev, sg, nelems, (enum dma_data_direction)direction);
}

+static inline void
+pci_dma_sync_to_device_single(struct pci_dev *hwdev, dma_addr_t dma_handle,
+ size_t size, int direction)
+{
+ dma_sync_to_device_single(hwdev == NULL ? NULL : &hwdev->dev, dma_handle, size, (enum dma_data_direction)direction);
+}
+
+static inline void
+pci_dma_sync_to_device_sg(struct pci_dev *hwdev, struct scatterlist *sg,
+ int nelems, int direction)
+{
+ dma_sync_to_device_sg(hwdev == NULL ? NULL : &hwdev->dev, sg, nelems, (enum dma_data_direction)direction);
+}
+
#endif
--- linux-2.6.0-test8/Documentation/DMA-mapping.txt Wed Oct 8 21:24:06 2003
+++ v2.6.0-test8-md/Documentation/DMA-mapping.txt Tue Oct 21 11:27:17 2003
@@ -543,8 +543,11 @@
all bus addresses.

If you need to use the same streaming DMA region multiple times and touch
-the data in between the DMA transfers, just map it with
-pci_map_{single,sg}, and after each DMA transfer call either:
+the data in between the DMA transfers, the buffer needs to be synced
+depending on the transfer direction.
+
+When reading from the device, just map it with pci_map_{single,sg},
+and after each DMA transfer call either:

pci_dma_sync_single(dev, dma_handle, size, direction);

@@ -553,6 +556,20 @@
pci_dma_sync_sg(dev, sglist, nents, direction);

as appropriate.
+
+When writing to the mapped the buffer, prepare the data and
+then before giving the buffer to the hardware call either:
+
+ pci_dma_sync_to_device_single(dev, dma_handle, size, direction);
+
+or:
+
+ pci_dma_sync_to_device_sg(dev, sglist, nents, direction);
+
+as appropriate.
+
+For bidirectional mappings the corresponding calls are required before and
+after passing ownership between cpu and hardware.

After the last DMA transfer call one of the DMA unmap routines
pci_unmap_{single,sg}. If you don't touch the data from the first pci_map_*
-
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