Messages in this thread Patch in this message | | | From | David Brownell <> | Subject | [patch 2.6.26-rc5-git] at91_nand speedup via {read,write}s{b,w}() | Date | Mon, 9 Jun 2008 03:13:28 -0700 |
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This uses __raw_{read,write}s{b,w}() primitives to access data on NAND chips for more efficient I/O.
On an arm926 with memory clocked at 100 MHz, this reduced the elapsed time for a 64 MByte read by 16%. ("dd" /dev/mtd0 to /dev/null, with an 8-bit NAND using hardware ECC and 128KB blocksize.)
Also some minor section tweaks:
- Use platform_driver_probe() so no pointer to probe() lingers after that code has been removed at run-time.
- Use __exit and __exit_p so the remove() code will normally be removed by the linker.
Since these buffer read/write calls are new, this increases the runtime code footprint (by 88 bytes on my build, after the section tweaks).
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> --- Yeah, this does may you wonder why the *default* nand r/w code isn't using these primitives; this speedup shouldn't be platform-specific.
Posting this now since I think this should either be incorporated into the new atmel_nand.c code or into drivers/mtd/nand/nand_base.c ... both arm and avr32 support these calls, I'm not sure whether or not some platforms don't support them.
drivers/mtd/nand/at91_nand.c | 46 ++++++++++++++++++++++++++++++++++++++----- 1 file changed, 41 insertions(+), 5 deletions(-)
--- a/drivers/mtd/nand/at91_nand.c 2008-04-28 11:05:34.000000000 -0700 +++ b/drivers/mtd/nand/at91_nand.c 2008-04-28 21:59:34.000000000 -0700 @@ -146,6 +146,37 @@ static void at91_nand_disable(struct at9 } /* + * Minimal-overhead PIO for data access. + */ +static void at91_read_buf(struct mtd_info *mtd, u8 *buf, int len) +{ + struct nand_chip *nand_chip = mtd->priv; + + __raw_readsb(nand_chip->IO_ADDR_R, buf, len); +} + +static void at91_read_buf16(struct mtd_info *mtd, u8 *buf, int len) +{ + struct nand_chip *nand_chip = mtd->priv; + + __raw_readsw(nand_chip->IO_ADDR_R, buf, len / 2); +} + +static void at91_write_buf(struct mtd_info *mtd, const u8 *buf, int len) +{ + struct nand_chip *nand_chip = mtd->priv; + + __raw_writesb(nand_chip->IO_ADDR_W, buf, len); +} + +static void at91_write_buf16(struct mtd_info *mtd, const u8 *buf, int len) +{ + struct nand_chip *nand_chip = mtd->priv; + + __raw_writesw(nand_chip->IO_ADDR_W, buf, len / 2); +} + +/* * write oob for small pages */ static int at91_nand_write_oob_512(struct mtd_info *mtd, @@ -440,8 +471,14 @@ static int __init at91_nand_probe(struct nand_chip->chip_delay = 20; /* 20us command delay time */ - if (host->board->bus_width_16) /* 16-bit bus width */ + if (host->board->bus_width_16) { /* 16-bit bus width */ nand_chip->options |= NAND_BUSWIDTH_16; + nand_chip->read_buf = at91_read_buf16; + nand_chip->write_buf = at91_write_buf16; + } else { + nand_chip->read_buf = at91_read_buf; + nand_chip->write_buf = at91_write_buf; + } platform_set_drvdata(pdev, host); at91_nand_enable(host); @@ -548,7 +585,7 @@ err_ecc_ioremap: /* * Remove a NAND device. */ -static int __devexit at91_nand_remove(struct platform_device *pdev) +static int __exit at91_nand_remove(struct platform_device *pdev) { struct at91_nand_host *host = platform_get_drvdata(pdev); struct mtd_info *mtd = &host->mtd; @@ -565,8 +602,7 @@ static int __devexit at91_nand_remove(st } static struct platform_driver at91_nand_driver = { - .probe = at91_nand_probe, - .remove = at91_nand_remove, + .remove = __exit_p(at91_nand_remove), .driver = { .name = "at91_nand", .owner = THIS_MODULE, @@ -575,7 +611,7 @@ static struct platform_driver at91_nand_ static int __init at91_nand_init(void) { - return platform_driver_register(&at91_nand_driver); + return platform_driver_probe(&at91_nand_driver, at91_nand_probe); }
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