forked from Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
141 lines
3.4 KiB
141 lines
3.4 KiB
// SPDX-License-Identifier: GPL-2.0-only |
|
/* |
|
* Sample fifo dma implementation |
|
* |
|
* Copyright (C) 2010 Stefani Seibold <[email protected]> |
|
*/ |
|
|
|
#include <linux/init.h> |
|
#include <linux/module.h> |
|
#include <linux/kfifo.h> |
|
|
|
/* |
|
* This module shows how to handle fifo dma operations. |
|
*/ |
|
|
|
/* fifo size in elements (bytes) */ |
|
#define FIFO_SIZE 32 |
|
|
|
static struct kfifo fifo; |
|
|
|
static int __init example_init(void) |
|
{ |
|
int i; |
|
unsigned int ret; |
|
unsigned int nents; |
|
struct scatterlist sg[10]; |
|
|
|
printk(KERN_INFO "DMA fifo test start\n"); |
|
|
|
if (kfifo_alloc(&fifo, FIFO_SIZE, GFP_KERNEL)) { |
|
printk(KERN_WARNING "error kfifo_alloc\n"); |
|
return -ENOMEM; |
|
} |
|
|
|
printk(KERN_INFO "queue size: %u\n", kfifo_size(&fifo)); |
|
|
|
kfifo_in(&fifo, "test", 4); |
|
|
|
for (i = 0; i != 9; i++) |
|
kfifo_put(&fifo, i); |
|
|
|
/* kick away first byte */ |
|
kfifo_skip(&fifo); |
|
|
|
printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo)); |
|
|
|
/* |
|
* Configure the kfifo buffer to receive data from DMA input. |
|
* |
|
* .--------------------------------------. |
|
* | 0 | 1 | 2 | ... | 12 | 13 | ... | 31 | |
|
* |---|------------------|---------------| |
|
* \_/ \________________/ \_____________/ |
|
* \ \ \ |
|
* \ \_allocated data \ |
|
* \_*free space* \_*free space* |
|
* |
|
* We need two different SG entries: one for the free space area at the |
|
* end of the kfifo buffer (19 bytes) and another for the first free |
|
* byte at the beginning, after the kfifo_skip(). |
|
*/ |
|
sg_init_table(sg, ARRAY_SIZE(sg)); |
|
nents = kfifo_dma_in_prepare(&fifo, sg, ARRAY_SIZE(sg), FIFO_SIZE); |
|
printk(KERN_INFO "DMA sgl entries: %d\n", nents); |
|
if (!nents) { |
|
/* fifo is full and no sgl was created */ |
|
printk(KERN_WARNING "error kfifo_dma_in_prepare\n"); |
|
return -EIO; |
|
} |
|
|
|
/* receive data */ |
|
printk(KERN_INFO "scatterlist for receive:\n"); |
|
for (i = 0; i < nents; i++) { |
|
printk(KERN_INFO |
|
"sg[%d] -> " |
|
"page %p offset 0x%.8x length 0x%.8x\n", |
|
i, sg_page(&sg[i]), sg[i].offset, sg[i].length); |
|
|
|
if (sg_is_last(&sg[i])) |
|
break; |
|
} |
|
|
|
/* put here your code to setup and exectute the dma operation */ |
|
/* ... */ |
|
|
|
/* example: zero bytes received */ |
|
ret = 0; |
|
|
|
/* finish the dma operation and update the received data */ |
|
kfifo_dma_in_finish(&fifo, ret); |
|
|
|
/* Prepare to transmit data, example: 8 bytes */ |
|
nents = kfifo_dma_out_prepare(&fifo, sg, ARRAY_SIZE(sg), 8); |
|
printk(KERN_INFO "DMA sgl entries: %d\n", nents); |
|
if (!nents) { |
|
/* no data was available and no sgl was created */ |
|
printk(KERN_WARNING "error kfifo_dma_out_prepare\n"); |
|
return -EIO; |
|
} |
|
|
|
printk(KERN_INFO "scatterlist for transmit:\n"); |
|
for (i = 0; i < nents; i++) { |
|
printk(KERN_INFO |
|
"sg[%d] -> " |
|
"page %p offset 0x%.8x length 0x%.8x\n", |
|
i, sg_page(&sg[i]), sg[i].offset, sg[i].length); |
|
|
|
if (sg_is_last(&sg[i])) |
|
break; |
|
} |
|
|
|
/* put here your code to setup and exectute the dma operation */ |
|
/* ... */ |
|
|
|
/* example: 5 bytes transmitted */ |
|
ret = 5; |
|
|
|
/* finish the dma operation and update the transmitted data */ |
|
kfifo_dma_out_finish(&fifo, ret); |
|
|
|
ret = kfifo_len(&fifo); |
|
printk(KERN_INFO "queue len: %u\n", kfifo_len(&fifo)); |
|
|
|
if (ret != 7) { |
|
printk(KERN_WARNING "size mismatch: test failed"); |
|
return -EIO; |
|
} |
|
printk(KERN_INFO "test passed\n"); |
|
|
|
return 0; |
|
} |
|
|
|
static void __exit example_exit(void) |
|
{ |
|
kfifo_free(&fifo); |
|
} |
|
|
|
module_init(example_init); |
|
module_exit(example_exit); |
|
MODULE_LICENSE("GPL"); |
|
MODULE_AUTHOR("Stefani Seibold <[email protected]>");
|
|
|