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Commit 23a346ca authored by David Brownell's avatar David Brownell Committed by David Woodhouse
Browse files

[MTD] [NAND] atmel_nand speedup via {read,write}s{b,w}() 



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 MiB read by 16%.  ("dd" /dev/mtd0 to /dev/null, with an 8-bit
NAND using hardware ECC and 128KiB 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).

[haavard.skinnemoen@atmel.com: rebase onto atmel_nand rename]
Signed-off-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: default avatarHåvard Skinnemoen <haavard.skinnemoen@atmel.com>
Acked-by: default avatarAndrew Victor <linux@maxim.org.za>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarDavid Woodhouse <David.Woodhouse@intel.com>
parent 175428b2

drivers/mtd/nand/atmel_nand.c

+41 −5
Original line number Diff line number Diff line
@@ -141,6 +141,37 @@ static int atmel_nand_device_ready(struct mtd_info *mtd) 
	return gpio_get_value(host->board->rdy_pin);

}



/*

 * Minimal-overhead PIO for data access.

 */

static void atmel_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 atmel_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 atmel_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 atmel_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

 */
@@ -436,8 +467,14 @@ static int __init atmel_nand_probe(struct platform_device *pdev) 


	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 = atmel_read_buf16;

		nand_chip->write_buf = atmel_write_buf16;

	} else {

		nand_chip->read_buf = atmel_read_buf;

		nand_chip->write_buf = atmel_write_buf;

	}



	platform_set_drvdata(pdev, host);

	atmel_nand_enable(host);
@@ -546,7 +583,7 @@ static int __init atmel_nand_probe(struct platform_device *pdev) 
/*

 * Remove a NAND device.

 */

static int __devexit atmel_nand_remove(struct platform_device *pdev)

static int __exit atmel_nand_remove(struct platform_device *pdev)

{

	struct atmel_nand_host *host = platform_get_drvdata(pdev);

	struct mtd_info *mtd = &host->mtd;
@@ -564,8 +601,7 @@ static int __devexit atmel_nand_remove(struct platform_device *pdev) 
}



static struct platform_driver atmel_nand_driver = {

	.probe		= atmel_nand_probe,

	.remove		= atmel_nand_remove,

	.remove		= __exit_p(atmel_nand_remove),

	.driver		= {

		.name	= "atmel_nand",

		.owner	= THIS_MODULE,
@@ -574,7 +610,7 @@ static struct platform_driver atmel_nand_driver = { 


static int __init atmel_nand_init(void)

{

	return platform_driver_register(&atmel_nand_driver);

	return platform_driver_probe(&atmel_nand_driver, atmel_nand_probe);

}