fpga: Add scatterlist based programming
Requiring contiguous kernel memory is not a good idea, this is a limited
resource and allocation can fail under normal work loads.
This introduces a .write_sg op that supporting drivers can provide
to DMA directly from dis-contiguous memory and a new entry point
fpga_mgr_buf_load_sg that users can call to directly provide page
lists.
The full matrix of compatibility is provided, either the linear or sg
interface can be used by the user with a driver supporting either
interface.
A notable change for drivers is that the .write op can now be called
multiple times.
Signed-off-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Acked-by: Alan Tull <atull@opensource.altera.com>
Acked-by: Moritz Fischer <moritz.fischer@ettus.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/Documentation/fpga/fpga-mgr.txt b/Documentation/fpga/fpga-mgr.txt
index 86ee507..78f197f 100644
--- a/Documentation/fpga/fpga-mgr.txt
+++ b/Documentation/fpga/fpga-mgr.txt
@@ -22,7 +22,16 @@
struct fpga_image_info *info,
const char *buf, size_t count);
-Load the FPGA from an image which exists as a buffer in memory.
+Load the FPGA from an image which exists as a contiguous buffer in
+memory. Allocating contiguous kernel memory for the buffer should be avoided,
+users are encouraged to use the _sg interface instead of this.
+
+ int fpga_mgr_buf_load_sg(struct fpga_manager *mgr,
+ struct fpga_image_info *info,
+ struct sg_table *sgt);
+
+Load the FPGA from an image from non-contiguous in memory. Callers can
+construct a sg_table using alloc_page backed memory.
int fpga_mgr_firmware_load(struct fpga_manager *mgr,
struct fpga_image_info *info,
@@ -166,7 +175,7 @@
The programming sequence is:
1. .write_init
- 2. .write (may be called once or multiple times)
+ 2. .write or .write_sg (may be called once or multiple times)
3. .write_complete
The .write_init function will prepare the FPGA to receive the image data. The
@@ -176,7 +185,11 @@
The .write function writes a buffer to the FPGA. The buffer may be contain the
whole FPGA image or may be a smaller chunk of an FPGA image. In the latter
-case, this function is called multiple times for successive chunks.
+case, this function is called multiple times for successive chunks. This interface
+is suitable for drivers which use PIO.
+
+The .write_sg version behaves the same as .write except the input is a sg_table
+scatter list. This interface is suitable for drivers which use DMA.
The .write_complete function is called after all the image has been written
to put the FPGA into operating mode.