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Subject[PATCH v3 13/37] mtd: nand: denali: avoid hard-coding ecc.strength and ecc.bytes
Date
Another problem of this driver is hard-coded ecc.strength and
ecc.bytes. Currently ecc.bytes is defined as follows:

#define ECC_8BITS 14
#define ECC_15BITS 26

The parameters were hard-coded because only the following two cases
are possible on Intel platforms:

- ecc.size = 512, ecc.strength = 8 --> ecc.bytes = 14
- ecc.size = 512, ecc.strength = 15 --> ecc.bytes = 26

However, they are actually customizable parameters, for example,
UniPhier platform supports the following:

- ecc.size = 1024, ecc.strength = 8 --> ecc.bytes = 14
- ecc.size = 1024, ecc.strength = 16 --> ecc.bytes = 28
- ecc.size = 1024, ecc.strength = 24 --> ecc.bytes = 42

So, we need to handle these parameters in a more generic manner.
Fortunately, the Denali User's Guide explains how to calculate the
ecc.bytes. The formula is:

ecc.bytes = 2 * CEIL(13 * ecc.strength / 16) (for ecc.size = 512)
ecc.bytes = 2 * CEIL(14 * ecc.strength / 16) (for ecc.size = 1024)

This commit allows platforms to specify denali->ecc_strength_avail,
each bit of which represents supported ECC strength.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

Changes in v3: None
Changes in v2: None

drivers/mtd/nand/denali.c | 73 +++++++++++++++++++++++++++----------------
drivers/mtd/nand/denali.h | 1 +
drivers/mtd/nand/denali_dt.c | 3 ++
drivers/mtd/nand/denali_pci.c | 1 +
4 files changed, 51 insertions(+), 27 deletions(-)

diff --git a/drivers/mtd/nand/denali.c b/drivers/mtd/nand/denali.c
index 78d3b18..ce87b95 100644
--- a/drivers/mtd/nand/denali.c
+++ b/drivers/mtd/nand/denali.c
@@ -1344,13 +1344,45 @@ static void denali_hw_init(struct denali_nand_info *denali)
denali_irq_init(denali);
}

-/*
- * Althogh controller spec said SLC ECC is forceb to be 4bit,
- * but denali controller in MRST only support 15bit and 8bit ECC
- * correction
- */
-#define ECC_8BITS 14
-#define ECC_15BITS 26
+static int denali_calc_ecc_bytes(int ecc_size, int ecc_strength)
+{
+ WARN_ON(ecc_size != 512 && ecc_size != 1024);
+
+ return DIV_ROUND_UP(ecc_strength * (ecc_size == 512 ? 13 : 14), 16) * 2;
+}
+
+static int denali_set_max_ecc_strength(struct denali_nand_info *denali)
+{
+ struct nand_chip *chip = &denali->nand;
+ struct mtd_info *mtd = nand_to_mtd(chip);
+ int oobsize = mtd->oobsize;
+ int ecc_size = chip->ecc.size;
+ int ecc_steps = mtd->writesize / chip->ecc.size;
+ int ecc_strength, ecc_bytes;
+ int max_strength = 0;
+
+ /* carve out the BBM area */
+ oobsize -= denali->bbtskipbytes;
+
+ for_each_set_bit(ecc_strength, &denali->ecc_strength_avail,
+ sizeof(denali->ecc_strength_avail) * BITS_PER_BYTE) {
+ ecc_bytes = denali_calc_ecc_bytes(ecc_size, ecc_strength);
+ if (ecc_bytes * ecc_steps > oobsize)
+ break;
+
+ max_strength = ecc_strength;
+ }
+
+ if (!max_strength) {
+ dev_err(denali->dev,
+ "Your NAND chip OOB is too small. No available ECC strength.\n");
+ return -EINVAL;
+ }
+
+ chip->ecc.strength = max_strength;
+
+ return 0;
+}

static int denali_ooblayout_ecc(struct mtd_info *mtd, int section,
struct mtd_oob_region *oobregion)
@@ -1609,27 +1641,14 @@ int denali_init(struct denali_nand_info *denali)
goto failed_req_irq;
}

- /*
- * Denali Controller only support 15bit and 8bit ECC in MRST,
- * so just let controller do 15bit ECC for MLC and 8bit ECC for
- * SLC if possible.
- * */
- if (!nand_is_slc(chip) &&
- mtd->oobsize > denali->bbtskipbytes +
- ECC_15BITS * (mtd->writesize / chip->ecc.size)) {
- /* if MLC OOB size is large enough, use 15bit ECC*/
- chip->ecc.strength = 15;
- chip->ecc.bytes = ECC_15BITS;
- iowrite32(15, denali->flash_reg + ECC_CORRECTION);
- } else if (mtd->oobsize <
- denali->bbtskipbytes + ECC_8BITS * (mtd->writesize / chip->ecc.size)) {
- pr_err("Your NAND chip OOB is not large enough to contain 8bit ECC correction codes");
+ ret = denali_set_max_ecc_strength(denali);
+ if (ret)
goto failed_req_irq;
- } else {
- chip->ecc.strength = 8;
- chip->ecc.bytes = ECC_8BITS;
- iowrite32(8, denali->flash_reg + ECC_CORRECTION);
- }
+
+ chip->ecc.bytes = denali_calc_ecc_bytes(chip->ecc.size,
+ chip->ecc.strength);
+
+ iowrite32(chip->ecc.strength, denali->flash_reg + ECC_CORRECTION);

iowrite32(chip->ecc.size, denali->flash_reg + CFG_DATA_BLOCK_SIZE);
iowrite32(chip->ecc.size, denali->flash_reg + CFG_LAST_DATA_BLOCK_SIZE);
diff --git a/drivers/mtd/nand/denali.h b/drivers/mtd/nand/denali.h
index 7c24d82..00ce04e 100644
--- a/drivers/mtd/nand/denali.h
+++ b/drivers/mtd/nand/denali.h
@@ -348,6 +348,7 @@ struct denali_nand_info {
int bbtskipbytes;
int max_banks;
unsigned int revision;
+ unsigned long ecc_strength_avail;
unsigned int caps;
};

diff --git a/drivers/mtd/nand/denali_dt.c b/drivers/mtd/nand/denali_dt.c
index 1681a30..c3bc333 100644
--- a/drivers/mtd/nand/denali_dt.c
+++ b/drivers/mtd/nand/denali_dt.c
@@ -31,10 +31,12 @@ struct denali_dt {

struct denali_dt_data {
unsigned int revision;
+ unsigned long ecc_strength_avail;
unsigned int caps;
};

static const struct denali_dt_data denali_socfpga_data = {
+ .ecc_strength_avail = BIT(15) | BIT(8),
.caps = DENALI_CAP_HW_ECC_FIXUP |
DENALI_CAP_ECC_SIZE_512,
};
@@ -64,6 +66,7 @@ static int denali_dt_probe(struct platform_device *pdev)
data = of_device_get_match_data(&pdev->dev);
if (data) {
denali->revision = data->revision;
+ denali->ecc_strength_avail = data->ecc_strength_avail;
denali->caps = data->caps;
}

diff --git a/drivers/mtd/nand/denali_pci.c b/drivers/mtd/nand/denali_pci.c
index 5202a11..a1ee9f8 100644
--- a/drivers/mtd/nand/denali_pci.c
+++ b/drivers/mtd/nand/denali_pci.c
@@ -85,6 +85,7 @@ static int denali_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
goto failed_remap_reg;
}

+ denali->ecc_strength_avail = BIT(15) | BIT(8);
denali->caps |= DENALI_CAP_ECC_SIZE_512;

ret = denali_init(denali);
--
2.7.4
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