RE: writing environment in NAND flash

[Vanalme Filip <F.Vanalme@TELEVIC.com>]

> -----Original Message-----
> From: Vanalme Filip
> Sent: vrijdag 25 februari 2011 15:14
> To: Vanalme Filip; barebox@lists.infradead.org
> Subject: RE: writing environment in NAND flash
> 
> > -----Original Message-----
> > From: barebox-bounces@lists.infradead.org [mailto:barebox-
> > bounces@lists.infradead.org] On Behalf Of Vanalme Filip
> > Sent: vrijdag 25 februari 2011 14:50
> > To: barebox@lists.infradead.org
> > Subject: writing environment in NAND flash
> >
> > I have problems to save my environment settings. Although I set e.g. the MAC
> > address and some other values and do the saveenv command, after reset, all
> > settings have disappeared.
> > In the logging on the console port, I detected this :
> > "wrong crc on env
> > no valid environment found on /dev/env0. Using default environment"
> >
> > That will be, of course, the cause why the settings disappear.
> > Further investigation with debugging enabled in nand_imx.c showed that
> Barebox
> > reads 4 pages when starting up (0x80..0x83). That looks OK, because the
> > environment's size is 6156 bytes. So, indeen 4 pages needed. However, when
> > saving the environment, I only see appear one page write, i.e. on page 0x80. Of
> > course, when reading back the four pages, the 2nd, 3rd and 4th page have all
> FF
> > because they have never been written (causing a wrong CRC). Any idea why I
> > only see 1 page write when saving the environment although the size is 6156
> > bytes ? Any hints where to look in the sources ?
> >
> > Thanks in advance !
> >
> >
> >
> > Filip
> >
> [Filip]  Sorry for sending this message twice to the mailing list....
> 
> I have found the cause of this problem.
> I have CONFIG_MTD_NAND_VERIFY_WRITE=y.
> So, after a write, the code performs a read to verify the written data. For i.MX27, this
> mean that the function imx_nand_very_buf() is called. Well, that function looks
> like this :
> 
> static int
> imx_nand_verify_buf (struct mtd_info *mtd, const u_char * buf, int len) {
>   return -EFAULT;
> }
> 
> Yep...verification always fails... !
> Must be a function that still is under development, no ? (although I would have
> expected a "TODO" somewhere in that function....).
> 
> Two things I can do : set the configuration flag to n or add code to this function to
> really verify the written data.

[Filip] 
I changed the code in nand_imx.c like this :

* This function is used by the upper layer to verify the data in NAND Flash
 * with the data in the \b buf.
 *
 * @param       mtd     MTD structure for the NAND Flash
 * @param       buf     data to be verified
 * @param       len     length of the data to be verified
 *
 * @return      -EFAULT if error else 0
 *
 */
static int
imx_nand_verify_buf(struct mtd_info *mtd, const u_char * buf, int len) {
  int i;
  struct nand_chip *chip = mtd->priv;
  struct imx_nand_host *host = chip->priv;

  for (i = 0; i < len; i++)
  {
    if (buf[i] != host->data_buf[i])
    {
      MTD_DEBUG(MTD_DEBUG_LEVEL0, "Verify failed on byte %d : 0x%0x <-> 0x%0x\n", i, buf[i], host->data_buf[i]);
      return -EFAULT;
    }
  }

  return 0;
}

It looks OK now. I can now save the environment.

Maybe someone can verify if this is correct. And maybe adjust the Barebox mainline sources like that ?

> 
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