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/*
* arch/sh/mm/pg-dma.c
*
* Fast clear_page()/copy_page() implementation using the SH DMAC
*
* Copyright (C) 2003 Paul Mundt
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*/
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <asm/semaphore.h>
#include <asm/mmu_context.h>
#include <asm/addrspace.h>
#include <asm/atomic.h>
#include <asm/page.h>
#include <asm/dma.h>
#include <asm/io.h>
/* Channel to use for page ops, must be dual-address mode capable. */
static int dma_channel = CONFIG_DMA_PAGE_OPS_CHANNEL;
static void copy_page_dma(void *to, void *from)
{
/*
* This doesn't seem to get triggered until further along in the
* boot process, at which point the DMAC is already initialized.
* Fix this in the same fashion as clear_page_dma() in the event
* that this crashes due to the DMAC not being initialized.
*/
flush_icache_range((unsigned long)from, PAGE_SIZE);
dma_write_page(dma_channel, (unsigned long)from, (unsigned long)to);
dma_wait_for_completion(dma_channel);
}
static void clear_page_dma(void *to)
{
extern unsigned long empty_zero_page[1024];
/*
* We get invoked quite early on, if the DMAC hasn't been initialized
* yet, fall back on the slow manual implementation.
*/
if (dma_info[dma_channel].chan != dma_channel) {
clear_page_slow(to);
return;
}
dma_write_page(dma_channel, (unsigned long)empty_zero_page,
(unsigned long)to);
/*
* FIXME: Something is a bit racy here, if we poll the counter right
* away, we seem to lock. flushing the page from the dcache doesn't
* seem to make a difference one way or the other, though either a full
* icache or dcache flush does.
*
* The location of this is important as well, and must happen prior to
* the completion loop but after the transfer was initiated.
*
* Oddly enough, this doesn't appear to be an issue for copy_page()..
*/
flush_icache_range((unsigned long)to, PAGE_SIZE);
dma_wait_for_completion(dma_channel);
}
static int __init pg_dma_init(void)
{
int ret;
ret = request_dma(dma_channel, "page ops");
if (ret != 0)
return ret;
copy_page = copy_page_dma;
clear_page = clear_page_dma;
return ret;
}
static void __exit pg_dma_exit(void)
{
free_dma(dma_channel);
}
module_init(pg_dma_init);
module_exit(pg_dma_exit);
MODULE_AUTHOR("Paul Mundt <lethal@linux-sh.org>");
MODULE_DESCRIPTION("Optimized page copy/clear routines using a dual-address mode capable DMAC channel");
MODULE_LICENSE("GPL");
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