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