linux-kernel - [PATCH RESEND 1/3] atmel_nand speedup via {read,write}s{b,w}()

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Message-Id: <1214655248-15707-1-git-send-email-haavard.skinnemoen@atmel.com>
Date:	Sat, 28 Jun 2008 14:14:06 +0200
From:	Haavard Skinnemoen <haavard.skinnemoen@...el.com>
To:	David Woodhouse <dwmw2@...radead.org>
Cc:	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
	David Brownell <david-b@...bell.net>,
	David Brownell <dbrownell@...rs.sourceforge.net>,
	Haavard Skinnemoen <haavard.skinnemoen@...el.com>
Subject: [PATCH RESEND 1/3] atmel_nand speedup via {read,write}s{b,w}()

From: David Brownell <david-b@...bell.net>

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@...rs.sourceforge.net>
[haavard.skinnemoen@...el.com: rebase onto atmel_nand rename]
Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@...el.com>
Acked-by: Andrew Victor <linux@...im.org.za>
---
Resending the series with Andrew's ACKs added, no other changes.

 drivers/mtd/nand/atmel_nand.c |   46 ++++++++++++++++++++++++++++++++++++----
 1 files changed, 41 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/nand/atmel_nand.c b/drivers/mtd/nand/atmel_nand.c
index 50700ab..4814fc9 100644
--- a/drivers/mtd/nand/atmel_nand.c
+++ b/drivers/mtd/nand/atmel_nand.c
@@ -142,6 +142,37 @@ static int atmel_nand_device_ready(struct mtd_info *mtd)
 }
 
 /*
+ * 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
  */
 static int atmel_nand_write_oob_512(struct mtd_info *mtd,
@@ -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 @@ err_nand_ioremap:
 /*
  * 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);
 }
 
 
-- 
1.5.5.4

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