mtd: get the ECC info from the Extended Parameter Page

[Linux-MTD Mailing List]

Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=6dcbe0cdd83fb5f77be4f44c9e06c535281c375a
Commit:     6dcbe0cdd83fb5f77be4f44c9e06c535281c375a
Parent:     5b40db68cb1bd14b3d5b159754c9c1bc3bdeb080
Author:     Huang Shijie <b32955 at freescale.com>
AuthorDate: Wed May 22 10:28:27 2013 +0800
Committer:  David Woodhouse <David.Woodhouse at intel.com>
CommitDate: Fri Aug 30 21:34:42 2013 +0100

    mtd: get the ECC info from the Extended Parameter Page
    
    Since the ONFI 2.1, the onfi spec adds the Extended Parameter Page
    to store the ECC info.
    
    The onfi spec tells us that if the nand chip's recommended ECC codeword
    size is not 512 bytes, then the @ecc_bits is 0xff. The host _SHOULD_ then
    read the Extended ECC information that is part of the extended parameter
    page to retrieve the ECC requirements for this device.
    
    This patch implement the reading of the Extended Parameter Page, and parses
    the sections for ECC type, and get the ECC info from the ECC section.
    
    Tested this patch with Micron MT29F64G08CBABAWP.
    
    Acked-by: Pekon Gupta <pekon at ti.com>
    Signed-off-by: Huang Shijie <b32955 at freescale.com>
    Reviewed-and-tested-by: Brian Norris <computersforpeace at gmail.com>
    Signed-off-by: Brian Norris <computersforpeace at gmail.com>
    Signed-off-by: David Woodhouse <David.Woodhouse at intel.com>
---
 drivers/mtd/nand/nand_base.c | 87 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 42d44bb..d8c723c 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -2848,6 +2848,78 @@ static u16 onfi_crc16(u16 crc, u8 const *p, size_t len)
 	return crc;
 }
 
+/* Parse the Extended Parameter Page. */
+static int nand_flash_detect_ext_param_page(struct mtd_info *mtd,
+		struct nand_chip *chip, struct nand_onfi_params *p)
+{
+	struct onfi_ext_param_page *ep;
+	struct onfi_ext_section *s;
+	struct onfi_ext_ecc_info *ecc;
+	uint8_t *cursor;
+	int ret = -EINVAL;
+	int len;
+	int i;
+
+	len = le16_to_cpu(p->ext_param_page_length) * 16;
+	ep = kmalloc(len, GFP_KERNEL);
+	if (!ep) {
+		ret = -ENOMEM;
+		goto ext_out;
+	}
+
+	/* Send our own NAND_CMD_PARAM. */
+	chip->cmdfunc(mtd, NAND_CMD_PARAM, 0, -1);
+
+	/* Use the Change Read Column command to skip the ONFI param pages. */
+	chip->cmdfunc(mtd, NAND_CMD_RNDOUT,
+			sizeof(*p) * p->num_of_param_pages , -1);
+
+	/* Read out the Extended Parameter Page. */
+	chip->read_buf(mtd, (uint8_t *)ep, len);
+	if ((onfi_crc16(ONFI_CRC_BASE, ((uint8_t *)ep) + 2, len - 2)
+		!= le16_to_cpu(ep->crc))) {
+		pr_debug("fail in the CRC.\n");
+		goto ext_out;
+	}
+
+	/*
+	 * Check the signature.
+	 * Do not strictly follow the ONFI spec, maybe changed in future.
+	 */
+	if (strncmp(ep->sig, "EPPS", 4)) {
+		pr_debug("The signature is invalid.\n");
+		goto ext_out;
+	}
+
+	/* find the ECC section. */
+	cursor = (uint8_t *)(ep + 1);
+	for (i = 0; i < ONFI_EXT_SECTION_MAX; i++) {
+		s = ep->sections + i;
+		if (s->type == ONFI_SECTION_TYPE_2)
+			break;
+		cursor += s->length * 16;
+	}
+	if (i == ONFI_EXT_SECTION_MAX) {
+		pr_debug("We can not find the ECC section.\n");
+		goto ext_out;
+	}
+
+	/* get the info we want. */
+	ecc = (struct onfi_ext_ecc_info *)cursor;
+
+	if (ecc->codeword_size) {
+		chip->ecc_strength_ds = ecc->ecc_bits;
+		chip->ecc_step_ds = 1 << ecc->codeword_size;
+	}
+
+	pr_info("ONFI extended param page detected.\n");
+	return 0;
+
+ext_out:
+	kfree(ep);
+	return ret;
+}
+
 /*
  * Check if the NAND chip is ONFI compliant, returns 1 if it is, 0 otherwise.
  */
@@ -2916,6 +2988,21 @@ static int nand_flash_detect_onfi(struct mtd_info *mtd, struct nand_chip *chip,
 	if (p->ecc_bits != 0xff) {
 		chip->ecc_strength_ds = p->ecc_bits;
 		chip->ecc_step_ds = 512;
+	} else if (chip->onfi_version >= 21 &&
+		(onfi_feature(chip) & ONFI_FEATURE_EXT_PARAM_PAGE)) {
+
+		/*
+		 * The nand_flash_detect_ext_param_page() uses the
+		 * Change Read Column command which maybe not supported
+		 * by the chip->cmdfunc. So try to update the chip->cmdfunc
+		 * now. We do not replace user supplied command function.
+		 */
+		if (mtd->writesize > 512 && chip->cmdfunc == nand_command)
+			chip->cmdfunc = nand_command_lp;
+
+		/* The Extended Parameter Page is supported since ONFI 2.1. */
+		if (nand_flash_detect_ext_param_page(mtd, chip, p))
+			pr_info("Failed to detect the extended param page.\n");
 	}
 
 	pr_info("ONFI flash detected\n");