[PATCH v3 fpga 3/4] fpga: Add scatterlist based programming

[Jason Gunthorpe]

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@xxxxxxxxxxxxxxxxxxxx>
---
 Documentation/fpga/fpga-mgr.txt |  19 +++-
 drivers/fpga/fpga-mgr.c         | 238 ++++++++++++++++++++++++++++++++++------
 include/linux/fpga/fpga-mgr.h   |   5 +
 3 files changed, 228 insertions(+), 34 deletions(-)

diff --git a/Documentation/fpga/fpga-mgr.txt b/Documentation/fpga/fpga-mgr.txt
index 86ee5078fd034f..78f197fadfd1b6 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.
diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c
index f0a69d3e60a584..30f9778d0632d2 100644
--- a/drivers/fpga/fpga-mgr.c
+++ b/drivers/fpga/fpga-mgr.c
@@ -1,4 +1,4 @@
-/*
+  /*
  * FPGA Manager Core
  *
  *  Copyright (C) 2013-2015 Altera Corporation
@@ -25,16 +25,106 @@
 #include <linux/of.h>
 #include <linux/mutex.h>
 #include <linux/slab.h>
+#include <linux/scatterlist.h>
+#include <linux/highmem.h>
 
 static DEFINE_IDA(fpga_mgr_ida);
 static struct class *fpga_mgr_class;
 
+/*
+ * Call the low level driver's write_init function.  This will do the
+ * device-specific things to get the FPGA into the state where it is ready to
+ * receive an FPGA image. The low level driver only gets to see the first
+ * initial_header_size bytes in the buffer.
+ */
+static int fpga_mgr_write_init_buf(struct fpga_manager *mgr,
+				   struct fpga_image_info *info,
+				   const char *buf, size_t count)
+{
+	int ret;
+
+	mgr->state = FPGA_MGR_STATE_WRITE_INIT;
+	if (!mgr->mops->initial_header_size)
+		ret = mgr->mops->write_init(mgr, info, NULL, 0);
+	else
+		ret = mgr->mops->write_init(
+		    mgr, info, buf, min(mgr->mops->initial_header_size, count));
+
+	if (ret) {
+		dev_err(&mgr->dev, "Error preparing FPGA for writing\n");
+		mgr->state = FPGA_MGR_STATE_WRITE_INIT_ERR;
+		return ret;
+	}
+
+	return 0;
+}
+
+static int fpga_mgr_write_init_sg(struct fpga_manager *mgr,
+				  struct fpga_image_info *info,
+				  struct sg_table *sgt)
+{
+	struct sg_mapping_iter miter;
+	size_t len;
+	char *buf;
+	int ret;
+
+	if (!mgr->mops->initial_header_size)
+		return fpga_mgr_write_init_buf(mgr, info, NULL, 0);
+
+	/*
+	 * First try to use miter to map the first fragment to access the
+	 * header, this is the typical path.
+	 */
+	sg_miter_start(&miter, sgt->sgl, sgt->nents, SG_MITER_FROM_SG);
+	if (sg_miter_next(&miter) &&
+	    miter.length >= mgr->mops->initial_header_size) {
+		ret = fpga_mgr_write_init_buf(mgr, info, miter.addr,
+					      miter.length);
+		sg_miter_stop(&miter);
+		return ret;
+	}
+	sg_miter_stop(&miter);
+
+	/* Otherwise copy the fragments into temporary memory. */
+	buf = kmalloc(mgr->mops->initial_header_size, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	len = sg_copy_to_buffer(sgt->sgl, sgt->nents, buf,
+				mgr->mops->initial_header_size);
+	ret = fpga_mgr_write_init_buf(mgr, info, buf, len);
+
+	kfree(buf);
+
+	return ret;
+}
+
+/*
+ * After all the FPGA image has been written, do the device specific steps to
+ * finish and set the FPGA into operating mode.
+ */
+static int fpga_mgr_write_complete(struct fpga_manager *mgr,
+				   struct fpga_image_info *info)
+{
+	int ret;
+
+	mgr->state = FPGA_MGR_STATE_WRITE_COMPLETE;
+	ret = mgr->mops->write_complete(mgr, info);
+	if (ret) {
+		dev_err(&mgr->dev, "Error after writing image data to FPGA\n");
+		mgr->state = FPGA_MGR_STATE_WRITE_COMPLETE_ERR;
+		return ret;
+	}
+	mgr->state = FPGA_MGR_STATE_OPERATING;
+
+	return 0;
+}
+
 /**
- * fpga_mgr_buf_load - load fpga from image in buffer
+ * fpga_mgr_buf_load_sg - load fpga from image in buffer from a scatter list
  * @mgr:	fpga manager
  * @info:	fpga image specific information
- * @buf:	buffer contain fpga image
- * @count:	byte count of buf
+ * @sgt:	scatterlist table
  *
  * Step the low level fpga manager through the device-specific steps of getting
  * an FPGA ready to be configured, writing the image to it, then doing whatever
@@ -42,54 +132,139 @@ static struct class *fpga_mgr_class;
  * mgr pointer from of_fpga_mgr_get() or fpga_mgr_get() and checked that it is
  * not an error code.
  *
+ * This is the preferred entry point for FPGA programming, it does not require
+ * any contiguous kernel memory.
+ *
  * Return: 0 on success, negative error code otherwise.
  */
-int fpga_mgr_buf_load(struct fpga_manager *mgr, struct fpga_image_info *info,
-		      const char *buf, size_t count)
+int fpga_mgr_buf_load_sg(struct fpga_manager *mgr, struct fpga_image_info *info,
+			 struct sg_table *sgt)
 {
-	struct device *dev = &mgr->dev;
 	int ret;
 
-	/*
-	 * Call the low level driver's write_init function.  This will do the
-	 * device-specific things to get the FPGA into the state where it is
-	 * ready to receive an FPGA image. The low level driver only gets to
-	 * see the first initial_header_size bytes in the buffer.
-	 */
-	mgr->state = FPGA_MGR_STATE_WRITE_INIT;
-	ret = mgr->mops->write_init(mgr, info, buf,
-				    min(mgr->mops->initial_header_size, count));
+	ret = fpga_mgr_write_init_sg(mgr, info, sgt);
+	if (ret)
+		return ret;
+
+	/* Write the FPGA image to the FPGA. */
+	mgr->state = FPGA_MGR_STATE_WRITE;
+	if (mgr->mops->write_sg) {
+		ret = mgr->mops->write_sg(mgr, sgt);
+	} else {
+		struct sg_mapping_iter miter;
+
+		sg_miter_start(&miter, sgt->sgl, sgt->nents, SG_MITER_FROM_SG);
+		while (sg_miter_next(&miter)) {
+			ret = mgr->mops->write(mgr, miter.addr, miter.length);
+			if (ret)
+				break;
+		}
+		sg_miter_stop(&miter);
+	}
+
 	if (ret) {
-		dev_err(dev, "Error preparing FPGA for writing\n");
-		mgr->state = FPGA_MGR_STATE_WRITE_INIT_ERR;
+		dev_err(&mgr->dev, "Error while writing image data to FPGA\n");
+		mgr->state = FPGA_MGR_STATE_WRITE_ERR;
 		return ret;
 	}
 
+	return fpga_mgr_write_complete(mgr, info);
+}
+EXPORT_SYMBOL_GPL(fpga_mgr_buf_load_sg);
+
+static int fpga_mgr_buf_load_mapped(struct fpga_manager *mgr,
+				    struct fpga_image_info *info,
+				    const char *buf, size_t count)
+{
+	int ret;
+
+	ret = fpga_mgr_write_init_buf(mgr, info, buf, count);
+	if (ret)
+		return ret;
+
 	/*
 	 * Write the FPGA image to the FPGA.
 	 */
 	mgr->state = FPGA_MGR_STATE_WRITE;
 	ret = mgr->mops->write(mgr, buf, count);
 	if (ret) {
-		dev_err(dev, "Error while writing image data to FPGA\n");
+		dev_err(&mgr->dev, "Error while writing image data to FPGA\n");
 		mgr->state = FPGA_MGR_STATE_WRITE_ERR;
 		return ret;
 	}
 
+	return fpga_mgr_write_complete(mgr, info);
+}
+
+/**
+ * fpga_mgr_buf_load - load fpga from image in buffer
+ * @mgr:	fpga manager
+ * @flags:	flags setting fpga confuration modes
+ * @buf:	buffer contain fpga image
+ * @count:	byte count of buf
+ *
+ * Step the low level fpga manager through the device-specific steps of getting
+ * an FPGA ready to be configured, writing the image to it, then doing whatever
+ * post-configuration steps necessary.  This code assumes the caller got the
+ * mgr pointer from of_fpga_mgr_get() and checked that it is not an error code.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int fpga_mgr_buf_load(struct fpga_manager *mgr, struct fpga_image_info *info,
+		      const char *buf, size_t count)
+{
+	struct page **pages;
+	struct sg_table sgt;
+	const void *p;
+	int nr_pages;
+	int index;
+	int rc;
+
 	/*
-	 * After all the FPGA image has been written, do the device specific
-	 * steps to finish and set the FPGA into operating mode.
+	 * This is just a fast path if the caller has already created a
+	 * contiguous kernel buffer and the driver doesn't require SG, non-SG
+	 * drivers will still work on the slow path.
 	 */
-	mgr->state = FPGA_MGR_STATE_WRITE_COMPLETE;
-	ret = mgr->mops->write_complete(mgr, info);
-	if (ret) {
-		dev_err(dev, "Error after writing image data to FPGA\n");
-		mgr->state = FPGA_MGR_STATE_WRITE_COMPLETE_ERR;
-		return ret;
+	if (mgr->mops->write)
+		return fpga_mgr_buf_load_mapped(mgr, info, buf, count);
+
+	/*
+	 * Convert the linear kernel pointer into a sg_table of pages for use
+	 * by the driver.
+	 */
+	nr_pages = DIV_ROUND_UP((unsigned long)buf + count, PAGE_SIZE) -
+		   (unsigned long)buf / PAGE_SIZE;
+	pages = kmalloc_array(nr_pages, sizeof(struct page *), GFP_KERNEL);
+	if (!pages)
+		return -ENOMEM;
+
+	p = buf - offset_in_page(buf);
+	for (index = 0; index < nr_pages; index++) {
+		if (is_vmalloc_addr(p))
+			pages[index] = vmalloc_to_page(p);
+		else
+			pages[index] = kmap_to_page((void *)p);
+		if (!pages[index]) {
+			kfree(pages);
+			return -EFAULT;
+		}
+		p += PAGE_SIZE;
 	}
-	mgr->state = FPGA_MGR_STATE_OPERATING;
 
-	return 0;
+	/*
+	 * The temporary pages list is used to code share the merging algorithm
+	 * in sg_alloc_table_from_pages
+	 */
+	rc = sg_alloc_table_from_pages(&sgt, pages, index, offset_in_page(buf),
+				       count, GFP_KERNEL);
+	kfree(pages);
+	if (rc)
+		return rc;
+
+	rc = fpga_mgr_buf_load_sg(mgr, info, &sgt);
+	sg_free_table(&sgt);
+
+	return rc;
 }
 EXPORT_SYMBOL_GPL(fpga_mgr_buf_load);
 
@@ -291,8 +466,9 @@ int fpga_mgr_register(struct device *dev, const char *name,
 	struct fpga_manager *mgr;
 	int id, ret;
 
-	if (!mops || !mops->write_init || !mops->write ||
-	    !mops->write_complete || !mops->state) {
+	if (!mops || !mops->write_complete || !mops->state ||
+	    !mops->write_init || (!mops->write && !mops->write_sg) ||
+	    (mops->write && mops->write_sg)) {
 		dev_err(dev, "Attempt to register without fpga_manager_ops\n");
 		return -EINVAL;
 	}
diff --git a/include/linux/fpga/fpga-mgr.h b/include/linux/fpga/fpga-mgr.h
index 16551d5eac36a7..57beb5d09bfcb2 100644
--- a/include/linux/fpga/fpga-mgr.h
+++ b/include/linux/fpga/fpga-mgr.h
@@ -22,6 +22,7 @@
 #define _LINUX_FPGA_MGR_H
 
 struct fpga_manager;
+struct sg_table;
 
 /**
  * enum fpga_mgr_states - fpga framework states
@@ -88,6 +89,7 @@ struct fpga_image_info {
  * @state: returns an enum value of the FPGA's state
  * @write_init: prepare the FPGA to receive confuration data
  * @write: write count bytes of configuration data to the FPGA
+ * @write_sg: write the scatter list of configuration data to the FPGA
  * @write_complete: set FPGA to operating state after writing is done
  * @fpga_remove: optional: Set FPGA into a specific state during driver remove
  *
@@ -102,6 +104,7 @@ struct fpga_manager_ops {
 			  struct fpga_image_info *info,
 			  const char *buf, size_t count);
 	int (*write)(struct fpga_manager *mgr, const char *buf, size_t count);
+	int (*write_sg)(struct fpga_manager *mgr, struct sg_table *sgt);
 	int (*write_complete)(struct fpga_manager *mgr,
 			      struct fpga_image_info *info);
 	void (*fpga_remove)(struct fpga_manager *mgr);
@@ -129,6 +132,8 @@ struct fpga_manager {
 
 int fpga_mgr_buf_load(struct fpga_manager *mgr, struct fpga_image_info *info,
 		      const char *buf, size_t count);
+int fpga_mgr_buf_load_sg(struct fpga_manager *mgr, struct fpga_image_info *info,
+			 struct sg_table *sgt);
 
 int fpga_mgr_firmware_load(struct fpga_manager *mgr,
 			   struct fpga_image_info *info,
-- 
2.7.4