[patch] pci_dma_sync_to_device

* [patch] pci_dma_sync_to_device
@ 2003-10-21 10:37 Martin Diehl
  2003-10-21 13:33 ` Colin Ngam
  2003-10-22 10:59 ` David S. Miller
  0 siblings, 2 replies; 4+ messages in thread
From: Martin Diehl @ 2003-10-21 10:37 UTC (permalink / raw)
  To: David S. Miller; +Cc: linux-kernel


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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