[PATCH v4 RESEND] mm: cma: add a simple kernel module as the helper to test CMA

[PATCH v4 RESEND] mm: cma: add a simple kernel module as the helper to test CMA

[Barry Song]

From: Barry Song <Baohua.Song@csr.com>

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

1st time
$ echo 1024 > /dev/cma_test
will require cma_test to request 1MB(1024KB)
2nd time
$ echo 2048 > /dev/cma_test
will require cma_test to request 2MB(2048KB)

Any read request to /dev/cma_test will let the module to free the 1st valid
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
$ cat /dev/cma_test
will require cma_test to free the 2MB allocated in the second write request

Signed-off-by: Barry Song <Baohua.Song@csr.com>
Reviewed-by: Michal Nazarewicz <mina86@mina86.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 resend to Greg KH so that he can decide whether it should be placed at tools
 or drivers/misc;
 See the discussion thread:
 [1] https://lkml.org/lkml/2012/7/3/80
 [2] https://lkml.org/lkml/2012/7/3/224
 [3] https://lkml.org/lkml/2012/7/4/87

 tools/cma/Makefile   |   13 +++++
 tools/cma/cma_test.c |  140 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 153 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..7eb96db
--- /dev/null
+++ b/tools/cma/cma_test.c
@@ -0,0 +1,140 @@
+/*
+ * kernel module helper for testing CMA
+ *
+ * Copyright (c) 2012 Cambridge Silicon Radio Limited, a CSR plc group company.
+ *
+ * Licensed under GPLv2 or later.
+ */
+
+#include <linux/device.h>
+#include <linux/dma-mapping.h>
+#include <linux/fs.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+
+struct cma_allocation {
+	struct list_head list;
+	size_t size;
+	dma_addr_t dma;
+	void *virt;
+};
+
+static struct device *cma_dev;
+static LIST_HEAD(cma_allocations);
+static DEFINE_SPINLOCK(cma_lock);
+
+/*
+ * any read request will free the 1st allocated 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)
+{
+	struct cma_allocation *alloc = NULL;
+
+	spin_lock(&cma_lock);
+	if (!list_empty(&cma_allocations)) {
+		alloc = list_first_entry(&cma_allocations,
+			struct cma_allocation, list);
+		list_del(&alloc->list);
+	}
+	spin_unlock(&cma_lock);
+
+	if (!alloc)
+		return -EIDRM;
+
+	dma_free_coherent(cma_dev, alloc->size, alloc->virt,
+		alloc->dma);
+
+	_dev_info(cma_dev, "free: CM virt: %p dma: %p size:%zuK\n",
+		alloc->virt, (void *)alloc->dma, alloc->size / SZ_1K);
+	kfree(alloc);
+
+	return 0;
+}
+
+/*
+ * any write request will alloc a new coherent memory, eg.
+ * echo 1024 > /dev/cma_test
+ * will request 1024KiB by CMA
+ */
+static ssize_t
+cma_test_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
+{
+	struct cma_allocation *alloc;
+	unsigned long size;
+	int ret;
+
+	ret = kstrtoul_from_user(buf, count, 0, &size);
+	if (ret)
+		return ret;
+
+	if (!size)
+		return -EINVAL;
+
+	if (size > ~(size_t)0 / SZ_1K)
+		return -EOVERFLOW;
+
+	alloc = kmalloc(sizeof *alloc, GFP_KERNEL);
+	if (!alloc)
+		return -ENOMEM;
+
+	alloc->size = size * SZ_1K;
+	alloc->virt = dma_alloc_coherent(cma_dev, alloc->size,
+		&alloc->dma, GFP_KERNEL);
+
+	if (alloc->virt) {
+		_dev_info(cma_dev, "alloc: virt: %p dma: %p size: %zuK\n",
+			alloc->virt, (void *)alloc->dma, alloc->size / SZ_1K);
+
+		spin_lock(&cma_lock);
+		list_add_tail(&alloc->list, &cma_allocations);
+		spin_unlock(&cma_lock);
+
+		return count;
+	} else {
+		dev_err(cma_dev, "no mem in CMA area\n");
+		kfree(alloc);
+		return -ENOSPC;
+	}
+}
+
+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 = 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 0;
+}
+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@csr.com>");
+MODULE_DESCRIPTION("kernel module to help the test of CMA");
+MODULE_ALIAS("cma_test");
-- 
1.7.1



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[PATCH v4 RESEND] mm: cma: add a simple kernel module as the helper to test CMA

[Arnd Bergmann]

On Thursday 05 July 2012, Barry Song wrote:
> From: Barry Song <Baohua.Song@csr.com>
> 
> Any write request to /dev/cma_test will let the module to allocate memory from
> CMA, for example:
> 
> 1st time
> $ echo 1024 > /dev/cma_test
> will require cma_test to request 1MB(1024KB)
> 2nd time
> $ echo 2048 > /dev/cma_test
> will require cma_test to request 2MB(2048KB)
> 
> Any read request to /dev/cma_test will let the module to free the 1st valid
> 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
> $ cat /dev/cma_test
> will require cma_test to free the 2MB allocated in the second write request

I missed the earlier times this was posted and read up on it now.

> Signed-off-by: Barry Song <Baohua.Song@csr.com>
> Reviewed-by: Michal Nazarewicz <mina86@mina86.com>
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
>  resend to Greg KH so that he can decide whether it should be placed at tools
>  or drivers/misc;
>  See the discussion thread:
>  [1] https://lkml.org/lkml/2012/7/3/80
>  [2] https://lkml.org/lkml/2012/7/3/224
>  [3] https://lkml.org/lkml/2012/7/4/87

I think it should be in mm/cma-test.c, along with kmemleak-test.c. It would be nice
if you could add some code that just runs at boot time (or when the module is
loaded) and allocates and frees memory using CMA.

> +static struct device *cma_dev;

Do you actually need this device? It's not connected to hardware so
it doesn't actually do DMA and we might as well pass a NULL pointer
into dma_alloc_*().

> +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 = misc_register(&cma_test_misc);

A better place for this is really debugfs. The driver is not meant as a stable
kernel interface that applications can rely on, it's purely a debugging help.

Just make this

	ret = debugfs_create_file("cma-test", 0600, NULL, NULL, &cma_test_fops);



	Arnd

[PATCH v4 RESEND] mm: cma: add a simple kernel module as the helper to test CMA

[Barry Song]

Hi Arnd,

2012/7/5 Arnd Bergmann <arnd@arndb.de>:
>
> I think it should be in mm/cma-test.c, along with kmemleak-test.c. It would be nice
> if you could add some code that just runs at boot time (or when the module is
> loaded) and allocates and frees memory using CMA.
>
>> +static struct device *cma_dev;
>
> Do you actually need this device? It's not connected to hardware so
> it doesn't actually do DMA and we might as well pass a NULL pointer
> into dma_alloc_*().
>
>> +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 = misc_register(&cma_test_misc);
>
> A better place for this is really debugfs. The driver is not meant as a stable
> kernel interface that applications can rely on, it's purely a debugging help.
>
> Just make this
>
>         ret = debugfs_create_file("cma-test", 0600, NULL, NULL, &cma_test_fops);
>

we did have some discussions about this at:
http://www.spinics.net/lists/arm-kernel/msg163548.html

i'd say both are acceptable to me.

>         Arnd
>

-barry