Merge branch 'master' of git://git.denx.de/u-boot-video

[karo-tx-uboot.git] / doc / README.nand

diff --git a/doc/README.nand b/doc/README.nand
index 913e9b50b804535acf9adc5176cdaae4132e51a1..f1c20ff645688769a560bb4a4027b92cadd615ff 100644 (file)
--- a/doc/README.nand
+++ b/doc/README.nand
@@ -89,21 +89,29 @@ Commands:
 
 Configuration Options:
 
 
 Configuration Options:
 

+   CONFIG_SYS_NAND_U_BOOT_OFFS
+       NAND Offset from where SPL will read u-boot image. This is the starting
+       address of u-boot MTD partition in NAND.
+

    CONFIG_CMD_NAND
    CONFIG_CMD_NAND

-      Enables NAND support and commmands.
+      Enables NAND support and commands.

 
    CONFIG_CMD_NAND_TORTURE
       Enables the torture command (see description of this command below).
 
 
    CONFIG_CMD_NAND_TORTURE
       Enables the torture command (see description of this command below).
 

-   CONFIG_MTD_NAND_ECC_JFFS2
-      Define this if you want the Error Correction Code information in
-      the out-of-band data to be formatted to match the JFFS2 file system.
-      CONFIG_MTD_NAND_ECC_YAFFS would be another useful choice for
-      someone to implement.
-

    CONFIG_SYS_MAX_NAND_DEVICE
       The maximum number of NAND devices you want to support.
 
    CONFIG_SYS_MAX_NAND_DEVICE
       The maximum number of NAND devices you want to support.
 

+   CONFIG_SYS_NAND_MAX_ECCPOS
+      If specified, overrides the maximum number of ECC bytes
+      supported.  Useful for reducing image size, especially with SPL.
+      This must be at least 48 if nand_base.c is used.
+
+   CONFIG_SYS_NAND_MAX_OOBFREE
+      If specified, overrides the maximum number of free OOB regions
+      supported.  Useful for reducing image size, especially with SPL.
+      This must be at least 2 if nand_base.c is used.
+

    CONFIG_SYS_NAND_MAX_CHIPS
       The maximum number of NAND chips per device to be supported.
 
    CONFIG_SYS_NAND_MAX_CHIPS
       The maximum number of NAND chips per device to be supported.
 


@@ -128,15 +136,8 @@ Configuration Options:
       Example of new init to be added to the end of an existing driver
       init:
 
       Example of new init to be added to the end of an existing driver
       init:
 

-       /*
-        * devnum is the device number to be used in nand commands
-        * and in mtd->name.  Must be less than
-        * CONFIG_SYS_NAND_MAX_DEVICE.
-        */
-       mtd = &nand_info[devnum];
-

        /* chip is struct nand_chip, and is now provided by the driver. */
        /* chip is struct nand_chip, and is now provided by the driver. */

-       mtd->priv = &chip;
+       mtd = nand_to_mtd(&chip);

 
        /*
         * Fill in appropriate values if this driver uses these fields,
 
        /*
         * Fill in appropriate values if this driver uses these fields,


@@ -157,7 +158,11 @@ Configuration Options:
        if (nand_scan_tail(mtd))
                error out
 
        if (nand_scan_tail(mtd))
                error out
 

-       if (nand_register(devnum))
+       /*
+        * devnum is the device number to be used in nand commands
+        * and in mtd->name.  Must be less than CONFIG_SYS_NAND_MAX_DEVICE.
+        */
+       if (nand_register(devnum, mtd))

                error out
 
       In addition to providing more flexibility to the driver, it reduces
                error out
 
       In addition to providing more flexibility to the driver, it reduces


@@ -169,14 +174,116 @@ Configuration Options:
       Please convert your driver even if you don't need the extra
       flexibility, so that one day we can eliminate the old mechanism.
 
       Please convert your driver even if you don't need the extra
       flexibility, so that one day we can eliminate the old mechanism.
 

-NOTE:
-=====

 
 

-The current NAND implementation is based on what is in recent
-Linux kernels.  The old legacy implementation has been removed.
+   CONFIG_SYS_NAND_ONFI_DETECTION
+       Enables detection of ONFI compliant devices during probe.
+       And fetching device parameters flashed on device, by parsing
+       ONFI parameter page.
+
+   CONFIG_BCH
+       Enables software based BCH ECC algorithm present in lib/bch.c
+       This is used by SoC platforms which do not have built-in ELM
+       hardware engine required for BCH ECC correction.
+
+
+Platform specific options
+=========================
+   CONFIG_NAND_OMAP_GPMC
+       Enables omap_gpmc.c driver for OMAPx and AMxxxx platforms.
+       GPMC controller is used for parallel NAND flash devices, and can
+       do ECC calculation (not ECC error detection) for HAM1, BCH4, BCH8
+       and BCH16 ECC algorithms.
+
+   CONFIG_NAND_OMAP_ELM
+       Enables omap_elm.c driver for OMAPx and AMxxxx platforms.
+       ELM controller is used for ECC error detection (not ECC calculation)
+       of BCH4, BCH8 and BCH16 ECC algorithms.
+       Some legacy platforms like OMAP3xx do not have in-built ELM h/w engine,
+       thus such SoC platforms need to depend on software library for ECC error
+       detection. However ECC calculation on such plaforms would still be
+       done by GPMC controller.
+
+   CONFIG_SPL_NAND_AM33XX_BCH
+       Enables SPL-NAND driver (am335x_spl_bch.c) which supports ELM based
+        hardware ECC correction. This is useful for platforms which have ELM
+       hardware engine and use NAND boot mode.
+       Some legacy platforms like OMAP3xx do not have in-built ELM h/w engine,
+       so those platforms should use CONFIG_SPL_NAND_SIMPLE for enabling
+        SPL-NAND driver with software ECC correction support.
+
+   CONFIG_NAND_OMAP_ECCSCHEME
+       On OMAP platforms, this CONFIG specifies NAND ECC scheme.
+       It can take following values:
+       OMAP_ECC_HAM1_CODE_SW
+               1-bit Hamming code using software lib.
+               (for legacy devices only)
+       OMAP_ECC_HAM1_CODE_HW
+               1-bit Hamming code using GPMC hardware.
+               (for legacy devices only)
+       OMAP_ECC_BCH4_CODE_HW_DETECTION_SW
+               4-bit BCH code (unsupported)
+       OMAP_ECC_BCH4_CODE_HW
+               4-bit BCH code (unsupported)
+       OMAP_ECC_BCH8_CODE_HW_DETECTION_SW
+               8-bit BCH code with
+               - ecc calculation using GPMC hardware engine,
+               - error detection using software library.
+               - requires CONFIG_BCH to enable software BCH library
+               (For legacy device which do not have ELM h/w engine)
+       OMAP_ECC_BCH8_CODE_HW
+               8-bit BCH code with
+               - ecc calculation using GPMC hardware engine,
+               - error detection using ELM hardware engine.
+       OMAP_ECC_BCH16_CODE_HW
+               16-bit BCH code with
+               - ecc calculation using GPMC hardware engine,
+               - error detection using ELM hardware engine.
+
+       How to select ECC scheme on OMAP and AMxx platforms ?
+       -----------------------------------------------------
+       Though higher ECC schemes have more capability to detect and correct
+       bit-flips, but still selection of ECC scheme is dependent on following
+       - hardware engines present in SoC.
+               Some legacy OMAP SoC do not have ELM h/w engine thus such
+               SoC cannot support BCHx_HW ECC schemes.
+       - size of OOB/Spare region
+               With higher ECC schemes, more OOB/Spare area is required to
+               store ECC. So choice of ECC scheme is limited by NAND oobsize.
+
+       In general following expression can help:
+               NAND_OOBSIZE >= 2 + (NAND_PAGESIZE / 512) * ECC_BYTES
+       where
+               NAND_OOBSIZE    = number of bytes available in
+                               OOB/spare area per NAND page.
+               NAND_PAGESIZE   = bytes in main-area of NAND page.
+               ECC_BYTES       = number of ECC bytes generated to
+                               protect 512 bytes of data, which is:
+                               3 for HAM1_xx ecc schemes
+                               7 for BCH4_xx ecc schemes
+                               14 for BCH8_xx ecc schemes
+                               26 for BCH16_xx ecc schemes
+
+               example to check for BCH16 on 2K page NAND
+               NAND_PAGESIZE = 2048
+               NAND_OOBSIZE = 64
+               2 + (2048 / 512) * 26 = 106 > NAND_OOBSIZE
+               Thus BCH16 cannot be supported on 2K page NAND.
+
+               However, for 4K pagesize NAND
+               NAND_PAGESIZE = 4096
+               NAND_OOBSIZE = 224
+               ECC_BYTES = 26
+               2 + (4096 / 512) * 26 = 210 < NAND_OOBSIZE
+               Thus BCH16 can be supported on 4K page NAND.
+
+
+    CONFIG_NAND_OMAP_GPMC_PREFETCH
+       On OMAP platforms that use the GPMC controller
+       (CONFIG_NAND_OMAP_GPMC_PREFETCH), this options enables the code that
+       uses the prefetch mode to speed up read operations.

 
 

-If you have board code which used CONFIG_NAND_LEGACY, you'll need
-to convert to the current NAND interface for it to continue to work.
+NOTE:
+=====

 
 The Disk On Chip driver is currently broken and has been for some time.
 There is a driver in drivers/mtd/nand, taken from Linux, that works with
 
 The Disk On Chip driver is currently broken and has been for some time.
 There is a driver in drivers/mtd/nand, taken from Linux, that works with


@@ -200,7 +307,7 @@ Miscellaneous and testing commands:
   DANGEROUS!!! Factory set bad blocks will be lost. Use only
   to remove artificial bad blocks created with the "markbad" command.
 
   DANGEROUS!!! Factory set bad blocks will be lost. Use only
   to remove artificial bad blocks created with the "markbad" command.
 

-  "torture offset"
+  "torture offset [size]"

   Torture block to determine if it is still reliable.
   Enabled by the CONFIG_CMD_NAND_TORTURE configuration option.
   This command returns 0 if the block is still reliable, else 1.
   Torture block to determine if it is still reliable.
   Enabled by the CONFIG_CMD_NAND_TORTURE configuration option.
   This command returns 0 if the block is still reliable, else 1.


@@ -217,6 +324,10 @@ Miscellaneous and testing commands:
   automate actions following a nand->write() error. This would e.g. be required
   in order to program or update safely firmware to NAND, especially for the UBI
   part of such firmware.
   automate actions following a nand->write() error. This would e.g. be required
   in order to program or update safely firmware to NAND, especially for the UBI
   part of such firmware.

+  Optionally, a second parameter size can be given to test multiple blocks with
+  one call. If size is not a multiple of the NAND's erase size, then the block
+  that contains offset + size will be tested in full. If used with size, this
+  command returns 0 if all tested blocks have been found reliable, else 1.

 
 
 NAND locking command (for chips with active LOCKPRE pin)
 
 
 NAND locking command (for chips with active LOCKPRE pin)