1/*
2 * arch/sh/mm/pg-dma.c
3 *
4 * Fast clear_page()/copy_page() implementation using the SH DMAC
5 *
6 * Copyright (C) 2003  Paul Mundt
7 *
8 * This file is subject to the terms and conditions of the GNU General Public
9 * License.  See the file "COPYING" in the main directory of this archive
10 * for more details.
11 */
12#include <linux/init.h>
13#include <linux/kernel.h>
14#include <linux/module.h>
15#include <asm/semaphore.h>
16#include <asm/mmu_context.h>
17#include <asm/addrspace.h>
18#include <asm/atomic.h>
19#include <asm/page.h>
20#include <asm/dma.h>
21#include <asm/io.h>
22
23/* Channel to use for page ops, must be dual-address mode capable. */
24static int dma_channel = CONFIG_DMA_PAGE_OPS_CHANNEL;
25
26static void copy_page_dma(void *to, void *from)
27{
28	/*
29	 * This doesn't seem to get triggered until further along in the
30	 * boot process, at which point the DMAC is already initialized.
31	 * Fix this in the same fashion as clear_page_dma() in the event
32	 * that this crashes due to the DMAC not being initialized.
33	 */
34
35	flush_icache_range((unsigned long)from, PAGE_SIZE);
36	dma_write_page(dma_channel, (unsigned long)from, (unsigned long)to);
37	dma_wait_for_completion(dma_channel);
38}
39
40static void clear_page_dma(void *to)
41{
42	/*
43	 * We get invoked quite early on, if the DMAC hasn't been initialized
44	 * yet, fall back on the slow manual implementation.
45	 */
46	if (dma_info[dma_channel].chan != dma_channel) {
47		clear_page_slow(to);
48		return;
49	}
50
51	dma_write_page(dma_channel, (unsigned long)empty_zero_page,
52				    (unsigned long)to);
53
54	flush_icache_range((unsigned long)to, PAGE_SIZE);
55
56	dma_wait_for_completion(dma_channel);
57}
58
59static int __init pg_dma_init(void)
60{
61	int ret;
62
63	ret = request_dma(dma_channel, "page ops");
64	if (ret != 0)
65		return ret;
66
67	copy_page = copy_page_dma;
68	clear_page = clear_page_dma;
69
70	return ret;
71}
72
73static void __exit pg_dma_exit(void)
74{
75	free_dma(dma_channel);
76}
77
78module_init(pg_dma_init);
79module_exit(pg_dma_exit);
80
81MODULE_AUTHOR("Paul Mundt <lethal@linux-sh.org>");
82MODULE_DESCRIPTION("Optimized page copy/clear routines using a dual-address mode capable DMAC channel");
83MODULE_LICENSE("GPL");
84