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

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

[Haavard Skinnemoen]

From: David Brownell <david-b@pacbell.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@users.sourceforge.net>
[haavard.skinnemoen@atmel.com: rebase onto atmel_nand rename]
Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
---
Another round of patches for the newly renamed Atmel NAND driver
coming up. I'm hoping this can join the existing bunch of patches for
2.6.27.

Out of curiosity, how did you solve the merge conflict with the ARM
tree?

Haavard

 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);
 }
 
 
-- 
1.5.5.3

[PATCH 2/3] atmel_nand: Work around AT32AP7000 ECC errata

[Haavard Skinnemoen]

The ALE signal isn't correctly wired up to the ECC controller on the
AP7000, so it starts calculating ECC during the address cycles.

Work around this by resetting the ECC controller between the address and
data cycles.

Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
---
 drivers/mtd/nand/atmel_nand.c |   25 +++++++++++++++++++++++--
 1 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/nand/atmel_nand.c b/drivers/mtd/nand/atmel_nand.c
index 4814fc9..99aec46 100644
--- a/drivers/mtd/nand/atmel_nand.c
+++ b/drivers/mtd/nand/atmel_nand.c
@@ -33,6 +33,7 @@
 #include <linux/io.h>
 
 #include <asm/arch/board.h>
+#include <asm/arch/cpu.h>
 
 #ifdef CONFIG_MTD_NAND_ATMEL_ECC_HW
 #define hard_ecc	1
@@ -264,6 +265,19 @@ static int atmel_nand_read_page(struct mtd_info *mtd,
 	uint8_t *ecc_pos;
 	int stat;
 
+	/*
+	 * Errata: ALE is incorrectly wired up to the ECC controller
+	 * on the AP7000, so it will include the address cycles in the
+	 * ECC calculation.
+	 *
+	 * Workaround: Reset the parity registers before reading the
+	 * actual data.
+	 */
+	if (cpu_is_at32ap7000()) {
+		struct atmel_nand_host *host = chip->priv;
+		ecc_writel(host->ecc, CR, ATMEL_ECC_RST);
+	}
+
 	/* read the page */
 	chip->read_buf(mtd, p, eccsize);
 
@@ -377,9 +391,16 @@ static int atmel_nand_correct(struct mtd_info *mtd, u_char *dat,
 }
 
 /*
- * Enable HW ECC : unsused
+ * Enable HW ECC : unused on most chips
  */
-static void atmel_nand_hwctl(struct mtd_info *mtd, int mode) { ; }
+static void atmel_nand_hwctl(struct mtd_info *mtd, int mode)
+{
+	if (cpu_is_at32ap7000()) {
+		struct nand_chip *nand_chip = mtd->priv;
+		struct atmel_nand_host *host = nand_chip->priv;
+		ecc_writel(host->ecc, CR, ATMEL_ECC_RST);
+	}
+}
 
 #ifdef CONFIG_MTD_PARTITIONS
 static const char *part_probes[] = { "cmdlinepart", NULL };
-- 
1.5.5.3

[PATCH 3/3] MTD: atmel_nand can be modular

[Haavard Skinnemoen]

From: David Brownell <dbrownell@users.sourceforge.net>

There's no reason to prevent the Atmel NAND driver from
building as a module.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
---
 drivers/mtd/nand/Kconfig |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/mtd/nand/Kconfig b/drivers/mtd/nand/Kconfig
index d8c0d86..71406e5 100644
--- a/drivers/mtd/nand/Kconfig
+++ b/drivers/mtd/nand/Kconfig
@@ -272,7 +272,7 @@ config MTD_NAND_CS553X
 	  If you say "m", the module will be called "cs553x_nand.ko".
 
 config MTD_NAND_ATMEL
-	bool "Support for NAND Flash / SmartMedia on AT91 and AVR32"
+	tristate "Support for NAND Flash / SmartMedia on AT91 and AVR32"
 	depends on ARCH_AT91 || AVR32
 	help
 	  Enables support for NAND Flash / Smart Media Card interface
-- 
1.5.5.3

Re: [PATCH 3/3] MTD: atmel_nand can be modular

[Andrew Victor]

hi Haavard,

> There's no reason to prevent the Atmel NAND driver from
> building as a module.

Acked-by: Andrew Victor <linux@maxim.org.za>

Re: [PATCH 2/3] atmel_nand: Work around AT32AP7000 ECC errata

[Andrew Victor]

hi Haavard,

> The ALE signal isn't correctly wired up to the ECC controller on the
> AP7000, so it starts calculating ECC during the address cycles.

Shouldn't affect the AT91's, so
  Acked-by: Andrew Victor <linux@maxim.org.za>

You might want to also change/remove the comment where the ECC hwctl()
function is registered.
It's currently:
   nand_chip->ecc.hwctl = at91_nand_hwctl;     /* unused */


Regards,
  Andrew Victor

Re: [PATCH 1/3] atmel_nand speedup via {read,write}s{b,w}()

[Andrew Victor]

hi Haavard,

> This uses __raw_{read,write}s{b,w}() primitives to access data on NAND
> chips for more efficient I/O.

This patch of David's has been in the AT91 tree for a while now.

So,
  Acked-by: Andrew Victor <linux@maxim.org.za>


Regards,
  Andrew