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authorJason Gunthorpe <jgunthorpe@obsidianresearch.com>2017-02-01 12:48:44 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-02-10 15:20:44 +0100
commitbaa6d396635129d8a67793e884f3b2182c7354b3 (patch)
treee836ac87b5a67011ef9f1c14d0443b4de8f9c309 /Documentation/fpga
parentb496df86ac1bbe393a55ddbfed35d46e74ef9767 (diff)
downloadlinux-next-baa6d396635129d8a67793e884f3b2182c7354b3.tar.gz
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>
Diffstat (limited to 'Documentation/fpga')
-rw-r--r--Documentation/fpga/fpga-mgr.txt19
1 files changed, 16 insertions, 3 deletions
diff --git a/Documentation/fpga/fpga-mgr.txt b/Documentation/fpga/fpga-mgr.txt
index 86ee5078fd03..78f197fadfd1 100644
--- a/Documentation/fpga/fpga-mgr.txt
+++ b/Documentation/fpga/fpga-mgr.txt
@@ -22,7 +22,16 @@ To program the FPGA from a file or from a buffer:
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 @@ success or negative error codes otherwise.
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 @@ buffer up at least this much before starting.
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.