On Mar 29, 2006, at 4:55 PM, Chris Leech wrote:
Provides an API for offloading memory copies to DMA devices
Signed-off-by: Chris Leech <[email protected]>
---
drivers/Kconfig | 2
drivers/Makefile | 1
drivers/dma/Kconfig | 13 +
drivers/dma/Makefile | 1
drivers/dma/dmaengine.c | 405 ++++++++++++++++++++++++++++++++++
+++++++++++
include/linux/dmaengine.h | 337 ++++++++++++++++++++++++++++++++++
+++
6 files changed, 759 insertions(+), 0 deletions(-)
diff --git a/drivers/Kconfig b/drivers/Kconfig
index 9f5c0da..f89ac05 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -72,4 +72,6 @@ source "drivers/edac/Kconfig"
source "drivers/rtc/Kconfig"
+source "drivers/dma/Kconfig"
+
endmenu
diff --git a/drivers/Makefile b/drivers/Makefile
index 4249552..9b808a6 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -74,3 +74,4 @@ obj-$(CONFIG_SGI_SN) += sn/
obj-y += firmware/
obj-$(CONFIG_CRYPTO) += crypto/
obj-$(CONFIG_SUPERH) += sh/
+obj-$(CONFIG_DMA_ENGINE) += dma/
diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
new file mode 100644
index 0000000..f9ac4bc
--- /dev/null
+++ b/drivers/dma/Kconfig
@@ -0,0 +1,13 @@
+#
+# DMA engine configuration
+#
+
+menu "DMA Engine support"
+
+config DMA_ENGINE
+ bool "Support for DMA engines"
+ ---help---
+ DMA engines offload copy operations from the CPU to dedicated
+ hardware, allowing the copies to happen asynchronously.
+
+endmenu
diff --git a/drivers/dma/Makefile b/drivers/dma/Makefile
new file mode 100644
index 0000000..10b7391
--- /dev/null
+++ b/drivers/dma/Makefile
@@ -0,0 +1 @@
+obj-y += dmaengine.o
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
new file mode 100644
index 0000000..683456a
--- /dev/null
+++ b/drivers/dma/dmaengine.c
@@ -0,0 +1,405 @@
+/*
+ * Copyright(c) 2004 - 2006 Intel Corporation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
modify it
+ * under the terms of the GNU General Public License as published
by the Free
+ * Software Foundation; either version 2 of the License, or (at
your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public
License along with
+ * this program; if not, write to the Free Software Foundation,
Inc., 59
+ * Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * The full GNU General Public License is included in this
distribution in the
+ * file called COPYING.
+ */
+
+/*
+ * This code implements the DMA subsystem. It provides a HW-
neutral interface
+ * for other kernel code to use asynchronous memory copy
capabilities,
+ * if present, and allows different HW DMA drivers to register as
providing
+ * this capability.
+ *
+ * Due to the fact we are accelerating what is already a
relatively fast
+ * operation, the code goes to great lengths to avoid additional
overhead,
+ * such as locking.
+ *
+ * LOCKING:
+ *
+ * The subsystem keeps two global lists, dma_device_list and
dma_client_list.
+ * Both of these are protected by a spinlock, dma_list_lock.
+ *
+ * Each device has a channels list, which runs unlocked but is
never modified
+ * once the device is registered, it's just setup by the driver.
+ *
+ * Each client has a channels list, it's only modified under the
client->lock
+ * and in an RCU callback, so it's safe to read under rcu_read_lock
().
+ *
+ * Each device has a kref, which is initialized to 1 when the
device is
+ * registered. A kref_put is done for each class_device
registered. When the
+ * class_device is released, the coresponding kref_put is done in
the release
+ * method. Every time one of the device's channels is allocated to
a client,
+ * a kref_get occurs. When the channel is freed, the coresponding
kref_put
+ * happens. The device's release function does a completion, so
+ * unregister_device does a remove event, class_device_unregister,
a kref_put
+ * for the first reference, then waits on the completion for all
other
+ * references to finish.
+ *
+ * Each channel has an open-coded implementation of Rusty
Russell's "bigref,"
+ * with a kref and a per_cpu local_t. A single reference is set
when on an
+ * ADDED event, and removed with a REMOVE event. Net DMA client
takes an
+ * extra reference per outstanding transaction. The relase
function does a
+ * kref_put on the device. -ChrisL
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/dmaengine.h>
+#include <linux/hardirq.h>
+#include <linux/spinlock.h>
+#include <linux/percpu.h>
+#include <linux/rcupdate.h>
+
+static DEFINE_SPINLOCK(dma_list_lock);
+static LIST_HEAD(dma_device_list);
+static LIST_HEAD(dma_client_list);
+
+/* --- sysfs implementation --- */
+
+static ssize_t show_memcpy_count(struct class_device *cd, char *buf)
+{
+ struct dma_chan *chan = container_of(cd, struct dma_chan,
class_dev);
+ unsigned long count = 0;
+ int i;
+
+ for_each_cpu(i)
+ count += per_cpu_ptr(chan->local, i)->memcpy_count;
+
+ return sprintf(buf, "%lu\n", count);
+}
+
+static ssize_t show_bytes_transferred(struct class_device *cd,
char *buf)
+{
+ struct dma_chan *chan = container_of(cd, struct dma_chan,
class_dev);
+ unsigned long count = 0;
+ int i;
+
+ for_each_cpu(i)
+ count += per_cpu_ptr(chan->local, i)->bytes_transferred;
+
+ return sprintf(buf, "%lu\n", count);
+}
+
What is the utility of exporting memcpy_count, and bytes_transferred
to userspace via sysfs? Is this really for debug (and thus should be
under debugfs?)
+static ssize_t show_in_use(struct class_device *cd, char *buf)
+{
+ struct dma_chan *chan = container_of(cd, struct dma_chan,
class_dev);
+
+ return sprintf(buf, "%d\n", (chan->client ? 1 : 0));
+}
+
+static struct class_device_attribute dma_class_attrs[] = {
+ __ATTR(memcpy_count, S_IRUGO, show_memcpy_count, NULL),
+ __ATTR(bytes_transferred, S_IRUGO, show_bytes_transferred, NULL),
+ __ATTR(in_use, S_IRUGO, show_in_use, NULL),
+ __ATTR_NULL
+};
+
[snip]
- kumar
-
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