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Message-ID: <op.wajuip2a3l0zgt@mpn-glaptop>
Date: Fri, 02 Mar 2012 16:26:39 +0100
From: "Michal Nazarewicz" <mina86@...a86.com>
To: m.szyprowski@...sung.com, "Barry Song" <Barry.Song@....com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
workgroup.linux@....com, "Barry Song" <Baohua.Song@....com>
Subject: Re: [PATCH] MM: CMA: add a simple kernel module as the helper to test
CMA
On Fri, 02 Mar 2012 03:52:22 +0100, Barry Song <Barry.Song@....com> wrote:
> From: Barry Song <Baohua.Song@....com>
>
> 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
Looks quite all right. It has a race condition but I guess for a test device it's
not that big of a deal (I think the race cannot cause panic). Either way, would be
nice if one could specify how much memory device should allocate. How about those
changes:
diff --git a/tools/cma/cma_test.c b/tools/cma/cma_test.c
index 3ee89f3..3d3b074 100644
--- a/tools/cma/cma_test.c
+++ b/tools/cma/cma_test.c
@@ -6,66 +6,96 @@
* Licensed under GPLv2 or later.
*/
-#include <linux/module.h>
#include <linux/device.h>
+#include <linux/dma-mapping.h>
#include <linux/fs.h>
+#include <linux/list.h>
#include <linux/miscdevice.h>
-#include <linux/dma-mapping.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+
+struct cma_allocation {
+ struct list_head list;
+ unsigned long size;
+ dma_addr_t dma;
+ void *virt;
+};
-#define CMA_NUM 10
static struct device *cma_dev;
-static dma_addr_t dma_phys[CMA_NUM];
-static void *dma_virt[CMA_NUM];
+static LIST_HEAD(cma_allocations);
+static DEFINE_SPINLOCK(cma_lock);
-/* any read request will free coherent memory, eg.
+/*
+ * Any read request will free a single 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;
- }
+ 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) {
+ dma_free_coherent(cma_dev, alloc->size, alloc->virt,
+ alloc->dma);
+ _dev_info(cma_dev, "free virt: %p phys: %p\n",
+ alloc->phys, (void *)alloc->dma);
+ kfree(alloc);
+ }
+
return 0;
}
/*
- * any write request will alloc coherent memory, eg.
- * echo 0 > /dev/cma_test
+ * Writes request specified number of pages, eg.
+ * echo 1024 > /dev/cma_test
*/
static ssize_t
-cma_test_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
+cma_test_write(struct file *file, const char __user *buf, size_t count,
+ loff_t *ppos)
{
- int i;
+ struct cma_allocation *alloc;
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;
- }
- }
+ alloc = kmalloc(sizeof *alloc, GFP_KERNEL);
+ if (!alloc)
+ return -ENOMEM;
+
+ ret = kstrtouint_from_user(buf, count, 0, &alloc->size);
+ if (ret)
+ return ret;
+
+ if (!alloc->size)
+ return -EINVAL;
+
+ if (alloc->size > (ULONG_MAX << PAGE_SHIFT))
+ return -EOVERFLOW;
- return count;
+ alloc->size >>= PAGE_SHIFT;
+ alloc->virt = dma_alloc_coherent(cma_dev, alloc->size,
+ &alloc->dma, GFP_KERNEL);
+
+ if (alloc->virt) {
+ _dev_info(cma_dev, "alloc virt: %p phys: %p\n", alloc->virt,
+ (void *)alloc->dma);
+
+ 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 = {
> Signed-off-by: Barry Song <Baohua.Song@....com>
> ---
> 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@....com>");
> +MODULE_DESCRIPTION("kernel module to help the test of CMA");
> +MODULE_ALIAS("CMA test");
--
Best regards, _ _
.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michał “mina86” Nazarewicz (o o)
ooo +----<email/xmpp: mpn@...gle.com>--------------ooO--(_)--Ooo--
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