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Subject[PATCH v6 10/10] mtd: gpmi: set the BCH's geometry with the ecc info
Date
If the nand chip provides us the ECC info, we can use it firstly.
The set_geometry_by_ecc_info() will use the ECC info, and
calculate the parameters we need.

Rename the old code to legacy_set_geometry() which will takes effect
when there is no ECC info from the nand chip or we fails in the ECC info case.

Signed-off-by: Huang Shijie <b32955@freescale.com>
---
drivers/mtd/nand/gpmi-nand/gpmi-nand.c | 132 +++++++++++++++++++++++++++++++-
1 files changed, 131 insertions(+), 1 deletions(-)

diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
index 25ecfa1..92c760b 100644
--- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
+++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
@@ -112,7 +112,132 @@ static inline bool gpmi_check_ecc(struct gpmi_nand_data *this)
return true;
}

-int common_nfc_set_geometry(struct gpmi_nand_data *this)
+/*
+ * If we can get the ECC information from the nand chip, we do not
+ * need to calculate them ourselves.
+ *
+ * We may have available oob space in this case.
+ */
+static bool set_geometry_by_ecc_info(struct gpmi_nand_data *this)
+{
+ struct bch_geometry *geo = &this->bch_geometry;
+ struct mtd_info *mtd = &this->mtd;
+ struct nand_chip *chip = mtd->priv;
+ struct nand_oobfree *of = gpmi_hw_ecclayout.oobfree;
+ unsigned int block_mark_bit_offset;
+
+ if (!(chip->ecc_strength_ds > 0 && chip->ecc_step_ds > 0))
+ return false;
+
+ switch (chip->ecc_step_ds) {
+ case SZ_512:
+ geo->gf_len = 13;
+ break;
+ case SZ_1K:
+ geo->gf_len = 14;
+ break;
+ default:
+ dev_err(this->dev,
+ "unsupported nand chip. ecc bits : %d, ecc size : %d\n",
+ chip->ecc_strength_ds, chip->ecc_step_ds);
+ return false;
+ }
+ geo->ecc_chunk_size = chip->ecc_step_ds;
+ geo->ecc_strength = round_up(chip->ecc_strength_ds, 2);
+ if (!gpmi_check_ecc(this))
+ return false;
+
+ /* Keep the C >= O */
+ if (geo->ecc_chunk_size < mtd->oobsize) {
+ dev_err(this->dev,
+ "unsupported nand chip. ecc size: %d, oob size : %d\n",
+ chip->ecc_step_ds, mtd->oobsize);
+ return false;
+ }
+
+ /* The default value, see comment in the legacy_set_geometry(). */
+ geo->metadata_size = 10;
+
+ geo->ecc_chunk_count = mtd->writesize / geo->ecc_chunk_size;
+
+ /*
+ * Now, the NAND chip with 2K page(data chunk is 512byte) shows below:
+ *
+ * | P |
+ * |<----------------------------------------------------->|
+ * | |
+ * | (Block Mark) |
+ * | P' | | | |
+ * |<-------------------------------------------->| D | | O' |
+ * | |<---->| |<--->|
+ * V V V V V
+ * +---+----------+-+----------+-+----------+-+----------+-+-----+
+ * | M | data |E| data |E| data |E| data |E| |
+ * +---+----------+-+----------+-+----------+-+----------+-+-----+
+ * ^ ^
+ * | O |
+ * |<------------>|
+ * | |
+ *
+ * P : the page size for BCH module.
+ * E : The ECC strength.
+ * G : the length of Galois Field.
+ * N : The chunk count of per page.
+ * M : the metasize of per page.
+ * C : the ecc chunk size, aka the "data" above.
+ * P': the nand chip's page size.
+ * O : the nand chip's oob size.
+ * O': the free oob.
+ *
+ * The formula for P is :
+ *
+ * E * G * N
+ * P = ------------ + P' + M
+ * 8
+ *
+ * The position of block mark moves forward in the ECC-based view
+ * of page, and the delta is:
+ *
+ * E * G * (N - 1)
+ * D = (---------------- + M)
+ * 8
+ *
+ * Please see the comment in legacy_set_geometry().
+ * With the condition C >= O , we still can get same result.
+ * So the bit position of the physical block mark within the ECC-based
+ * view of the page is :
+ * (P' - D) * 8
+ */
+ geo->page_size = mtd->writesize + geo->metadata_size +
+ (geo->gf_len * geo->ecc_strength * geo->ecc_chunk_count) / 8;
+
+ /* The available oob size we have. */
+ if (geo->page_size < mtd->writesize + mtd->oobsize) {
+ of->offset = geo->page_size - mtd->writesize;
+ of->length = mtd->oobsize - of->offset;
+ mtd->oobavail = gpmi_hw_ecclayout.oobavail = of->length;
+ }
+
+ geo->payload_size = mtd->writesize;
+
+ geo->auxiliary_status_offset = ALIGN(geo->metadata_size, 4);
+ geo->auxiliary_size = ALIGN(geo->metadata_size, 4)
+ + ALIGN(geo->ecc_chunk_count, 4);
+
+ if (!this->swap_block_mark)
+ return true;
+
+ /* For bit swap. */
+ block_mark_bit_offset = mtd->writesize * 8 -
+ (geo->ecc_strength * geo->gf_len * (geo->ecc_chunk_count - 1)
+ + geo->metadata_size * 8);
+
+ geo->block_mark_byte_offset = block_mark_bit_offset / 8;
+ geo->block_mark_bit_offset = block_mark_bit_offset % 8;
+ return true;
+}
+
+static int legacy_set_geometry(struct gpmi_nand_data *this)
{
struct bch_geometry *geo = &this->bch_geometry;
struct mtd_info *mtd = &this->mtd;
@@ -224,6 +349,11 @@ int common_nfc_set_geometry(struct gpmi_nand_data *this)
return 0;
}

+int common_nfc_set_geometry(struct gpmi_nand_data *this)
+{
+ return set_geometry_by_ecc_info(this) ? 0 : legacy_set_geometry(this);
+}
+
struct dma_chan *get_dma_chan(struct gpmi_nand_data *this)
{
int chipnr = this->current_chip;
--
1.7.1



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