4 * Fast clear_page()/copy_page() implementation using the SH DMAC
6 * Copyright (C) 2003 Paul Mundt
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
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>
23 /* Channel to use for page ops, must be dual-address mode capable. */
24 static int dma_channel
= CONFIG_DMA_PAGE_OPS_CHANNEL
;
26 static void copy_page_dma(void *to
, void *from
)
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.
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
);
40 static void clear_page_dma(void *to
)
43 * We get invoked quite early on, if the DMAC hasn't been initialized
44 * yet, fall back on the slow manual implementation.
46 if (dma_info
[dma_channel
].chan
!= dma_channel
) {
51 dma_write_page(dma_channel
, (unsigned long)empty_zero_page
,
55 * FIXME: Something is a bit racy here, if we poll the counter right
56 * away, we seem to lock. flushing the page from the dcache doesn't
57 * seem to make a difference one way or the other, though either a full
58 * icache or dcache flush does.
60 * The location of this is important as well, and must happen prior to
61 * the completion loop but after the transfer was initiated.
63 * Oddly enough, this doesn't appear to be an issue for copy_page()..
65 flush_icache_range((unsigned long)to
, PAGE_SIZE
);
67 dma_wait_for_completion(dma_channel
);
70 static int __init
pg_dma_init(void)
74 ret
= request_dma(dma_channel
, "page ops");
78 copy_page
= copy_page_dma
;
79 clear_page
= clear_page_dma
;
84 static void __exit
pg_dma_exit(void)
86 free_dma(dma_channel
);
89 module_init(pg_dma_init
);
90 module_exit(pg_dma_exit
);
92 MODULE_AUTHOR("Paul Mundt <lethal@linux-sh.org>");
93 MODULE_DESCRIPTION("Optimized page copy/clear routines using a dual-address mode capable DMAC channel");
94 MODULE_LICENSE("GPL");