[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: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Håvard Skinnemoen <haavard.skinnemoen@atmel.com>
Acked-by: Andrew Victor <linux@maxim.org.za>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 41 insertions, 5 deletions

diff --git a/drivers/mtd/nand/atmel_nand.c b/drivers/mtd/nand/atmel_nand.c
index 50700ab5a57a..4814fc9b237b 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);
 }