[PATCH] MM: CMA: add a simple kernel module as the helper to test CMA

[Barry Song]

From: Barry Song <Baohua.Song@xxxxxxx>

Any write request to /dev/cma_test will let the module to allocate memory from
CMA, for example:

1st time
$ echo 0 > /dev/cma_test
will require cma_test to request 1MB
2nd time
$ echo 0 > /dev/cma_test
will require cma_test to request 2MB

Any read request to /dev/cma_test will let the module to free memory from CMA,
for example:

1st time
$ cat /dev/cma_test
will require cma_test to free the 1MB allocated in the first write request
2nd time
$ echo 0 > /dev/cma_test
will require cma_test to free the 2MB allocated in the second write request

Signed-off-by: Barry Song <Baohua.Song@xxxxxxx>
---
 tools/cma/Makefile   |   13 ++++++
 tools/cma/cma_test.c |  108 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 121 insertions(+), 0 deletions(-)
 create mode 100644 tools/cma/Makefile
 create mode 100644 tools/cma/cma_test.c

diff --git a/tools/cma/Makefile b/tools/cma/Makefile
new file mode 100644
index 0000000..d15c2c0
--- /dev/null
+++ b/tools/cma/Makefile
@@ -0,0 +1,13 @@
+# Kernel modules
+#
+# To compile for ARM:
+# make ARCH=arm CC=arm-none-linux-gnueabi-gcc
+#
+obj-m	+= cma_test.o
+
+build: kernel_modules
+
+kernel_modules:
+	${MAKE} -C $(CURDIR)/../.. M=$(CURDIR)
+clean:
+	${MAKE} -C $(CURDIR)/../.. M=$(CURDIR) clean
diff --git a/tools/cma/cma_test.c b/tools/cma/cma_test.c
new file mode 100644
index 0000000..3ee89f3
--- /dev/null
+++ b/tools/cma/cma_test.c
@@ -0,0 +1,108 @@
+/*
+ * kernel module helper for testing CMA
+ *
+ * Copyright (c) 2011 Cambridge Silicon Radio Limited, a CSR plc group company.
+ *
+ * Licensed under GPLv2 or later.
+ */
+
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/miscdevice.h>
+#include <linux/dma-mapping.h>
+
+#define CMA_NUM  10
+static struct device *cma_dev;
+static dma_addr_t dma_phys[CMA_NUM];
+static void *dma_virt[CMA_NUM];
+
+/* any read request will free coherent memory, eg.
+ * cat /dev/cma_test
+ */
+static ssize_t
+cma_test_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
+{
+	int i;
+
+	for (i = 0; i < CMA_NUM; i++) {
+		if (dma_virt[i]) {
+			dma_free_coherent(cma_dev, (i + 1) * SZ_1M, dma_virt[i], dma_phys[i]);
+			_dev_info(cma_dev, "free virt: %p phys: %p\n", dma_virt[i], (void *)dma_phys[i]);
+			dma_virt[i] = NULL;
+			break;
+		}
+	}
+	return 0;
+}
+
+/*
+ * any write request will alloc coherent memory, eg.
+ * echo 0 > /dev/cma_test
+ */
+static ssize_t
+cma_test_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
+{
+	int i;
+	int ret;
+
+	for (i = 0; i < CMA_NUM; i++) {
+		if (!dma_virt[i]) {
+			dma_virt[i] = dma_alloc_coherent(cma_dev, (i + 1) * SZ_1M, &dma_phys[i], GFP_KERNEL);
+
+			if (dma_virt[i]) {
+				void *p;
+				/* touch every page in the allocated memory */
+				for (p = dma_virt[i]; p <  dma_virt[i] + (i + 1) * SZ_1M; p += PAGE_SIZE)
+					*(u32 *)p = 0;
+
+				_dev_info(cma_dev, "alloc virt: %p phys: %p\n", dma_virt[i], (void *)dma_phys[i]);
+			} else {
+				dev_err(cma_dev, "no mem in CMA area\n");
+				ret = -ENOMEM;
+			}
+			break;
+		}
+	}
+
+	return count;
+}
+
+static const struct file_operations cma_test_fops = {
+	.owner =    THIS_MODULE,
+	.read  =    cma_test_read,
+	.write =    cma_test_write,
+};
+
+static struct miscdevice cma_test_misc = {
+	.name = "cma_test",
+	.fops = &cma_test_fops,
+};
+
+static int __init cma_test_init(void)
+{
+	int ret = 0;
+
+	ret = misc_register(&cma_test_misc);
+	if (unlikely(ret)) {
+		pr_err("failed to register cma test misc device!\n");
+		return ret;
+	}
+	cma_dev = cma_test_misc.this_device;
+	cma_dev->coherent_dma_mask = ~0;
+	_dev_info(cma_dev, "registered.\n");
+
+	return ret;
+}
+module_init(cma_test_init);
+
+static void __exit cma_test_exit(void)
+{
+	misc_deregister(&cma_test_misc);
+}
+module_exit(cma_test_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Barry Song <Baohua.Song@xxxxxxx>");
+MODULE_DESCRIPTION("kernel module to help the test of CMA");
+MODULE_ALIAS("CMA test");
-- 
1.7.1



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