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Message-ID: <CAGsJ_4zz=C2k3pvc=1_=iviSUkz78QCF+yumEEMaknysLHFxag@mail.gmail.com>
Date: Fri, 2 Mar 2012 23:37:46 +0800
From: Barry Song <21cnbao@...il.com>
To: Michal Nazarewicz <mina86@...a86.com>
Cc: m.szyprowski@...sung.com, workgroup.linux@....com,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] MM: CMA: add a simple kernel module as the helper to test CMA
2012/3/2 Michal Nazarewicz <mina86@...a86.com>:
> 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:
Michal, i think these improvements have maken the cma_test much more
useful and flexible.
>
> 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--
>
>
-barry
--
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