Re: [U-Boot] [PATCH v7 1/5] mtd: nand: omap: enable BCH ECC scheme using ELM for generic platform

On Mon, 2013-09-30 at 19:43 +0530, Pekon Gupta wrote:

+Platform specific options +=========================

• CONFIG_NAND_OMAP_ECCSCHEME
• On OMAP platforms, this specifies NAND ECC scheme.
• 1 - HAM1_SW 1-bit Hamming code using software library

• 	(for legacy devices only)
  

• 2 - HAM1_HW 1-bit Hamming code using GPMC hardware engine

• 	(for legacy devices only)
  

• 3 - BCH4_SW 4-bit BCH code (unsupported)
• 4 - BCH4_HW 4-bit BCH code (unsupported)
• 5 - BCH8_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)
  

• 6 - BCH8_HW 8-bit BCH code with

• 	- ecc calculation using GPMC hardware engine,
  

• 	- error detection using ELM hardware engine.
  

You should document the symbols, not the numbers that happen to be assigned to them.

+/**

• • omap_select_ecc_scheme - configures driver for particular ecc-scheme
• • @nand: NAND chip device structure
• • @ecc_scheme: ecc scheme to configure
• • @pagesize: number of main-area bytes per page of NAND device
• • @oobsize: number of OOB/spare bytes per page of NAND device
• */

+static int omap_select_ecc_scheme(struct nand_chip *nand, int ecc_scheme,

• unsigned int pagesize, unsigned int oobsize) {
  

s/int ecc_scheme/enum omap_ecc ecc_scheme/

• struct nand_bch_priv *bch = nand->priv;
• struct nand_ecclayout *ecclayout = nand->ecc.layout;
• int i;
• switch (ecc_scheme) {
• case OMAP_ECC_HAM1_CODE_SW:

• debug("nand: selected OMAP_ECC_HAM1_CODE_SW\n");
  

• nand->ecc.mode		= NAND_ECC_SOFT;
  

• nand->ecc.layout	= NULL;
  

• nand->ecc.size		= 0;
  

• nand->ecc.strength	= 1;
  

• bch->ecc_scheme		= OMAP_ECC_HAM1_CODE_SW;
  

• break;
  

• case OMAP_ECC_HAM1_CODE_HW:

• debug("nand: selected OMAP_ECC_HAM1_CODE_HW\n");
  

• nand->ecc.mode		= NAND_ECC_HW;
  

• nand->ecc.strength	= 1;
  

• nand->ecc.size		= 512;
  

• nand->ecc.bytes		= 3;
  

• nand->ecc.hwctl		= omap_enable_hwecc;
  

• nand->ecc.correct	= omap_correct_data;
  

• nand->ecc.calculate	= omap_calculate_ecc;
  

• /* define ecc-layout */
  

• ecclayout->eccbytes	= nand->ecc.bytes *
  

• 				(pagesize / SECTOR_BYTES);
  

• for (i = 0; i < ecclayout->eccbytes; i++)
  

• 	ecclayout->eccpos[i] = i + BADBLOCK_MARKER_LENGTH;
  

• ecclayout->oobfree[0].offset = i + BADBLOCK_MARKER_LENGTH;
  

• ecclayout->oobfree[0].length = oobsize - ecclayout->eccbytes -
  

• 				BADBLOCK_MARKER_LENGTH;
  

• bch->ecc_scheme		= OMAP_ECC_HAM1_CODE_HW;
  

• break;
  

+#ifdef CONFIG_BCH

• case OMAP_ECC_BCH8_CODE_HW_DETECTION_SW:

• debug("nand: selected OMAP_ECC_BCH8_CODE_HW_DETECTION_SW\n");
  

• nand->ecc.mode		= NAND_ECC_HW;
  

• nand->ecc.strength	= 8;
  

• nand->ecc.size		= 512;
  

• nand->ecc.bytes		= 13;
  

• nand->ecc.hwctl		= omap_enable_ecc_bch;
  

• nand->ecc.correct	= omap_correct_data_bch_sw;
  

• nand->ecc.calculate	= omap_calculate_ecc_bch_sw;
  

• /* BCH SW library is used for error detection */
  

• bch_priv.control	= init_bch(13, 8, 0x201b);
  

• if (!bch_priv.control) {
  

• 	printf("nand: error: could not init_bch()\n");
  

• 	return -ENODEV;
  

• }
  

• bch_priv.type		= ECC_BCH8;
  

• /* define ecc-layout */
  

• ecclayout->eccbytes	= nand->ecc.bytes *
  

• 				(pagesize / SECTOR_BYTES);
  

• for (i = 0; i < ecclayout->eccbytes; i++)
  

• 	ecclayout->eccpos[i] = i + (oobsize -
  

• 				ecclayout->eccbytes);
  

• ecclayout->oobfree[0].offset = BADBLOCK_MARKER_LENGTH;
  

• ecclayout->oobfree[0].length = oobsize - ecclayout->eccbytes -
  

• 				BADBLOCK_MARKER_LENGTH;
  

• omap_hwecc_init_bch(nand, NAND_ECC_READ);
  

• bch->ecc_scheme		= OMAP_ECC_BCH8_CODE_HW_DETECTION_SW;
  

• break;
  

+#endif

• case OMAP_ECC_BCH8_CODE_HW:

• debug("nand: selected OMAP_ECC_BCH8_CODE_HW\n");
  

• nand->ecc.mode		= NAND_ECC_HW;
  

• nand->ecc.strength	= 8;
  

• nand->ecc.size		= 512;
  

• nand->ecc.bytes		= 14;
  

• nand->ecc.hwctl		= omap_enable_ecc_bch;
  

• nand->ecc.correct	= omap_correct_data_bch;
  

• nand->ecc.calculate	= omap_calculate_ecc_bch;
  

• nand->ecc.read_page	= omap_read_page_bch;
  

• /* ELM is used for ECC error detection */
  

• elm_init();
  

• bch_priv.type		= ECC_BCH8;
  

• /* define ecc-layout */
  

• ecclayout->eccbytes	= nand->ecc.bytes *
  

• 				(pagesize / SECTOR_BYTES);
  

• for (i = 0; i < ecclayout->eccbytes; i++)
  

• 	ecclayout->eccpos[i] = i + BADBLOCK_MARKER_LENGTH;
  

• ecclayout->oobfree[0].offset = i + BADBLOCK_MARKER_LENGTH;
  

• ecclayout->oobfree[0].length = oobsize - ecclayout->eccbytes -
  

• 				BADBLOCK_MARKER_LENGTH;
  

• bch->ecc_scheme		= OMAP_ECC_BCH8_CODE_HW;
  

• break;
  

• default:

• debug("nand: error: ecc scheme not enabled or supported\n");
  

• return -EINVAL;
  

• }
• /* check if NAND spare/OOB has enough bytes to accomodate ecclayout */
• if ((ecclayout->eccbytes + BADBLOCK_MARKER_LENGTH) > oobsize) {

• printf("nand: error: insufficient OOB bytes. require=%d\n", (
  

• 		ecclayout->eccbytes + BADBLOCK_MARKER_LENGTH));
  

• return -EINVAL;
  

• }

Check this before you make any changes to the current ECC setup.

• err = omap_select_ecc_scheme(nand, OMAP_ECC_HAM1_CODE_SW,
  

• 			mtd->writesize, mtd->oobsize);
  

• }
• if (err) {

• printf("nand: error: could not switch ecc, reverting\n");
  

• omap_select_ecc_scheme(nand, bch->ecc_scheme,
  

• 		       mtd->writesize, mtd->oobsize);
  

• return -EINVAL;
  

  }

You won't need to "revert" here if omap_select_ecc_scheme doesn't damage anything in error cases.

-Scott