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Diffstat (limited to 'arch/sh/mm/pg-dma.c')
| -rw-r--r-- | arch/sh/mm/pg-dma.c | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/arch/sh/mm/pg-dma.c b/arch/sh/mm/pg-dma.c new file mode 100644 index 0000000..1406d2e --- /dev/null +++ b/arch/sh/mm/pg-dma.c @@ -0,0 +1,97 @@ +/* + * 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"); + |