linux-kernel - [patch/resend 2.6.28-rc5] mtd m25p80: chip erase != block erase != sector erase

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Message-Id: <200811171138.48884.david-b@pacbell.net>
Date:	Mon, 17 Nov 2008 11:38:48 -0800
From:	David Brownell <david-b@...bell.net>
To:	Linux MTD <linux-mtd@...ts.infradead.org>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Chen Gong <g.chen@...escale.com>
Subject: [patch/resend 2.6.28-rc5] mtd m25p80: chip erase != block erase != sector erase

From: Chen Gong <g.chen@...escale.com>

This fixes broken terminology added in the "m25p80.c erase enhance" patch,
which added a chip erase command but called it "block erase".  There are
already two block erase commands; blocks are 4KiB or 32KiB.  There's also
a sector erase (usually 64 KiB).  Chip erase typically covers Megabytes.

  OPCODE_BE   ==> OPCODE_CHIP_ERASE
  erase_block ==> erase_chip

[dbrownell@...rs.sourceforge.net: update sector erase comments too ]

Signed-Off-by: Chen Gong <clumsycg@...il.com>
Signed-off-by: David Brownell <dbrownell@...rs.sourceforge.net>
---
 drivers/mtd/devices/m25p80.c |   23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

--- a/drivers/mtd/devices/m25p80.c
+++ b/drivers/mtd/devices/m25p80.c
@@ -37,9 +37,9 @@
 #define	OPCODE_NORM_READ	0x03	/* Read data bytes (low frequency) */
 #define	OPCODE_FAST_READ	0x0b	/* Read data bytes (high frequency) */
 #define	OPCODE_PP		0x02	/* Page program (up to 256 bytes) */
-#define	OPCODE_BE_4K 		0x20	/* Erase 4KiB block */
+#define	OPCODE_BE_4K		0x20	/* Erase 4KiB block */
 #define	OPCODE_BE_32K		0x52	/* Erase 32KiB block */
-#define	OPCODE_BE		0xc7	/* Erase whole flash block */
+#define	OPCODE_CHIP_ERASE	0xc7	/* Erase whole flash block */
 #define	OPCODE_SE		0xd8	/* Sector erase (usually 64KiB) */
 #define	OPCODE_RDID		0x9f	/* Read JEDEC ID */
 
@@ -167,7 +167,7 @@ static int wait_till_ready(struct m25p *
  *
  * Returns 0 if successful, non-zero otherwise.
  */
-static int erase_block(struct m25p *flash)
+static int erase_chip(struct m25p *flash)
 {
 	DEBUG(MTD_DEBUG_LEVEL3, "%s: %s %dKiB\n",
 			flash->spi->dev.bus_id, __func__,
@@ -181,7 +181,7 @@ static int erase_block(struct m25p *flas
 	write_enable(flash);
 
 	/* Set up command buffer. */
-	flash->command[0] = OPCODE_BE;
+	flash->command[0] = OPCODE_CHIP_ERASE;
 
 	spi_write(flash->spi, flash->command, 1);
 
@@ -250,15 +250,18 @@ static int m25p80_erase(struct mtd_info 
 
 	mutex_lock(&flash->lock);
 
-	/* REVISIT in some cases we could speed up erasing large regions
-	 * by using OPCODE_SE instead of OPCODE_BE_4K
-	 */
-
-	/* now erase those sectors */
-	if (len == flash->mtd.size && erase_block(flash)) {
+	/* whole-chip erase? */
+	if (len == flash->mtd.size && erase_chip(flash)) {
 		instr->state = MTD_ERASE_FAILED;
 		mutex_unlock(&flash->lock);
 		return -EIO;
+
+	/* REVISIT in some cases we could speed up erasing large regions
+	 * by using OPCODE_SE instead of OPCODE_BE_4K.  We may have set up
+	 * to use "small sector erase", but that's not always optimal.
+	 */
+
+	/* "sector"-at-a-time erase */
 	} else {
 		while (len) {
 			if (erase_sector(flash, addr)) {
--
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