[PATCH 2/2] drivers/mtd/devices/m25p80.c: Fix whole device erase

[PATCH 2/2] drivers/mtd/devices/m25p80.c: Fix whole device erase

[Cédric Cano]

From: Cédric Cano <ccano@interfaceconcept.com>

There are two ways to erase SPI Flash devices: sector per sector or the 
entire Flash (used when MTD partition is the whole Flash).

When the whole Flash is erased, the SPI command is sent to the device 
and the erase function ends. Then, when another access (read, write or 
erase) is done, a  wait of busy is performed that fails because of Flash 
erase time (can be more than 30s in case of whole erase).

This patch removes chip erase and use only sector per sector erase to 
erase the chip. When erase is performed, Flash accesses can be done.

C. Cano

Signed-off-by: Cédric Cano <ccano@interfaceconcept.com>
---

--- linux-3.5.3/drivers/mtd/devices/m25p80.c    2012-09-03 
18:03:35.787723207 +0200
+++ linux-3.5.3/drivers/mtd/devices/m25p80.c    2012-09-03 
18:01:17.455724709 +0200
@@ -202,31 +202,6 @@
      return -EBUSY;
  }

-/*
- * Erase the whole flash memory
- *
- * Returns 0 if successful, non-zero otherwise.
- */
-static int erase_chip(struct m25p *flash)
-{
-    pr_debug("%s: %s %lldKiB\n", dev_name(&flash->spi->dev), __func__,
-            (long long)(flash->mtd.size >> 10));
-
-    /* Wait until finished previous write command. */
-    if (wait_till_ready(flash))
-        return 1;
-
-    /* Send write enable, then erase commands. */
-    write_enable(flash);
-
-    /* Set up command buffer. */
-    flash->command[0] = OPCODE_CHIP_ERASE;
-
-    spi_write(flash->spi, flash->command, 1);
-
-    return 0;
-}
-
  static void m25p_addr2cmd(struct m25p *flash, unsigned int addr, u8 *cmd)
  {
      /* opcode is in cmd[0] */
@@ -301,33 +276,17 @@

      mutex_lock(&flash->lock);

-    /* whole-chip erase? */
-    if (len == flash->mtd.size) {
-        ret = erase_chip(flash);
+    /* "sector"-at-a-time erase */
+    while (len) {
+        ret = erase_sector(flash, addr);
          if (ret) {
              instr->state = MTD_ERASE_FAILED;
              mutex_unlock(&flash->lock);
              return ret;
          }

-    /* 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) {
-            ret = erase_sector(flash, addr)
-            if (ret) {
-                instr->state = MTD_ERASE_FAILED;
-                mutex_unlock(&flash->lock);
-                return ret;
-            }
-
-            addr += mtd->erasesize;
-            len -= mtd->erasesize;
-        }
+        addr += mtd->erasesize;
+        len -= mtd->erasesize;
      }

      mutex_unlock(&flash->lock);
---

Re: [PATCH 2/2] drivers/mtd/devices/m25p80.c: Fix whole device erase

[Artem Bityutskiy]

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On Mon, 2012-09-03 at 18:19 +0200, Cédric Cano wrote:
> From: Cédric Cano <ccano@interfaceconcept.com>
> 
> There are two ways to erase SPI Flash devices: sector per sector or the 
> entire Flash (used when MTD partition is the whole Flash).
> 
> When the whole Flash is erased, the SPI command is sent to the device 
> and the erase function ends. Then, when another access (read, write or 
> erase) is done, a  wait of busy is performed that fails because of Flash 
> erase time (can be more than 30s in case of whole erase).
> 
> This patch removes chip erase and use only sector per sector erase to 
> erase the chip. When erase is performed, Flash accesses can be done.

Please, re-send the patch with a better commit message which not only
explains _what_ you do, but also _why_ you do this, which problem you
solve, and what is the impact of the patch.

-- 
Best Regards,
Artem Bityutskiy

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