[PATCH v4 3/4] mtd: nand: gpmi: add proper raw access support
From: computersforpeace@gmail.com (Brian Norris)
Date: 2014-11-20 09:08:15
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On Mon, Oct 20, 2014 at 10:46:16AM +0200, Boris Brezillon wrote:
quoted hunk ↗ jump to hunk
Several MTD users (either in user or kernel space) expect a valid raw access support to NAND chip devices. This is particularly true for testing tools which are often touching the data stored in a NAND chip in raw mode to artificially generate errors. The GPMI drivers do not implemenent raw access functions, and thus rely on default HW_ECC scheme implementation. The default implementation consider the data and OOB area as properly separated in their respective NAND section, which is not true for the GPMI controller. In this driver/controller some OOB data are stored at the beginning of the NAND data area (these data are called metadata in the driver), then ECC bytes are interleaved with data chunk (which is similar to the HW_ECC_SYNDROME scheme), and eventually the remaining bytes are used as OOB data. Signed-off-by: Boris Brezillon <redacted> --- drivers/mtd/nand/gpmi-nand/gpmi-nand.c | 128 +++++++++++++++++++++++++++++++++ drivers/mtd/nand/gpmi-nand/gpmi-nand.h | 2 + 2 files changed, 130 insertions(+)diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c index 959cb9b..bd4dedc 100644 --- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c +++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c@@ -791,6 +791,7 @@ static void gpmi_free_dma_buffer(struct gpmi_nand_data *this) this->page_buffer_phys); kfree(this->cmd_buffer); kfree(this->data_buffer_dma); + kfree(this->raw_buffer); this->cmd_buffer = NULL; this->data_buffer_dma = NULL;@@ -837,6 +838,9 @@ static int gpmi_alloc_dma_buffer(struct gpmi_nand_data *this) if (!this->page_buffer_virt) goto error_alloc; + this->raw_buffer = kzalloc(mtd->writesize + mtd->oobsize, GFP_KERNEL); + if (!this->raw_buffer) + goto error_alloc; /* Slice up the page buffer. */ this->payload_virt = this->page_buffer_virt;@@ -1347,6 +1351,128 @@ gpmi_ecc_write_oob(struct mtd_info *mtd, struct nand_chip *chip, int page) return status & NAND_STATUS_FAIL ? -EIO : 0; } +static int gpmi_ecc_read_page_raw(struct mtd_info *mtd, + struct nand_chip *chip, uint8_t *buf, + int oob_required, int page)
I think I follow what this function is doing, and gpmi-nand notes the ECC layout elsewhere in the driver, but can you put a few comments at above this function to describe what it's doing? Refer to existing comments as needed. And maybe note the tricky parts inline with the code.
+{
+ struct gpmi_nand_data *this = chip->priv;
+ struct bch_geometry *nfc_geo = &this->bch_geometry;
+ int eccsize = nfc_geo->ecc_chunk_size;
+ int eccbits = nfc_geo->ecc_strength * nfc_geo->gf_len;
+ u8 *tmp_buf = this->raw_buffer;
+ size_t src_bit_off;
+ size_t oob_bit_off;
+ size_t oob_byte_off;
+ uint8_t *oob = chip->oob_poi;
+ int step;
+
+ chip->read_buf(mtd, tmp_buf,
+ mtd->writesize + mtd->oobsize);
+
+ if (this->swap_block_mark) {
+ u8 swap = tmp_buf[0];
+
+ tmp_buf[0] = tmp_buf[mtd->writesize];
+ tmp_buf[mtd->writesize] = swap;
+ }
+
+ if (oob_required)
+ memcpy(oob, tmp_buf, nfc_geo->metadata_size);
+
+ oob_bit_off = nfc_geo->metadata_size * 8;
+ src_bit_off = oob_bit_off;
+
+ for (step = 0; step < nfc_geo->ecc_chunk_count; step++) {
+ if (buf)Can buf ever be zero here?
+ gpmi_move_bits(buf, step * eccsize * 8,
+ tmp_buf, src_bit_off,
+ eccsize * 8);
+ src_bit_off += eccsize * 8;
+
+ if (oob_required)
+ gpmi_move_bits(oob, oob_bit_off,
+ tmp_buf, src_bit_off,
+ eccbits);
+
+ src_bit_off += eccbits;
+ oob_bit_off += eccbits;
+ }
+
+ if (oob_required) {
+ if (oob_bit_off % 8)
+ oob[oob_bit_off / 8] &= GENMASK(oob_bit_off - 1, 0);So you're manufacturing a few 0 bits here, right? Is that safe? Would we prefer to manufacture 1 bits, as if they are "erased"?
+ + oob_byte_off = DIV_ROUND_UP(oob_bit_off, 8); + + if (oob_byte_off < mtd->oobsize)
Extra whitespace before '<'.
+ memcpy(oob + oob_byte_off, + tmp_buf + mtd->writesize + oob_byte_off, + mtd->oobsize - oob_byte_off); + } + + return 0; +} + +static int gpmi_ecc_write_page_raw(struct mtd_info *mtd, + struct nand_chip *chip, + const uint8_t *buf, + int oob_required)
Same comment applies, about commenting the function.
+{
+ struct gpmi_nand_data *this = chip->priv;
+ struct bch_geometry *nfc_geo = &this->bch_geometry;
+ int eccsize = nfc_geo->ecc_chunk_size;
+ int eccbits = nfc_geo->ecc_strength * nfc_geo->gf_len;
+ u8 *tmp_buf = this->raw_buffer;
+ uint8_t *oob = chip->oob_poi;
+ size_t dst_bit_off;
+ size_t oob_bit_off;
+ size_t oob_byte_off;
+ int step;
+
+ if (!buf || !oob_required)Can buf be zero?
+ memset(tmp_buf, 0xff, mtd->writesize + mtd->oobsize);
+
+ memcpy(tmp_buf, oob, nfc_geo->metadata_size);
+ oob_bit_off = nfc_geo->metadata_size * 8;
+ dst_bit_off = oob_bit_off;
+
+ for (step = 0; step < nfc_geo->ecc_chunk_count; step++) {
+ if (buf)Again, can buf be zero?
quoted hunk ↗ jump to hunk
+ gpmi_move_bits(tmp_buf, dst_bit_off, + buf, step * eccsize * 8, eccsize * 8); + dst_bit_off += eccsize * 8; + + /* Pad last ECC block to align following data on a byte */ + if (step == nfc_geo->ecc_chunk_count - 1 && + (oob_bit_off + eccbits) % 8) + eccbits += 8 - ((oob_bit_off + eccbits) % 8); + + if (oob_required) + gpmi_move_bits(tmp_buf, dst_bit_off, + oob, oob_bit_off, eccbits); + + dst_bit_off += eccbits; + oob_bit_off += eccbits; + } + + oob_byte_off = oob_bit_off / 8; + + if (oob_required && oob_byte_off < mtd->oobsize) + memcpy(tmp_buf + mtd->writesize + oob_byte_off, + oob + oob_byte_off, mtd->oobsize - oob_byte_off); + + if (this->swap_block_mark) { + u8 swap = tmp_buf[0]; + + tmp_buf[0] = tmp_buf[mtd->writesize]; + tmp_buf[mtd->writesize] = swap; + } + + chip->write_buf(mtd, tmp_buf, mtd->writesize + mtd->oobsize); + + return 0; +} + static int gpmi_block_markbad(struct mtd_info *mtd, loff_t ofs) { struct nand_chip *chip = mtd->priv;@@ -1664,6 +1790,8 @@ static int gpmi_init_last(struct gpmi_nand_data *this) ecc->write_page = gpmi_ecc_write_page; ecc->read_oob = gpmi_ecc_read_oob; ecc->write_oob = gpmi_ecc_write_oob; + ecc->read_page_raw = gpmi_ecc_read_page_raw; + ecc->write_page_raw = gpmi_ecc_write_page_raw; ecc->mode = NAND_ECC_HW; ecc->size = bch_geo->ecc_chunk_size; ecc->strength = bch_geo->ecc_strength;diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.h b/drivers/mtd/nand/gpmi-nand/gpmi-nand.h index 17d0736..89ab5c8 100644 --- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.h +++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.h@@ -189,6 +189,8 @@ struct gpmi_nand_data { void *auxiliary_virt; dma_addr_t auxiliary_phys; + void *raw_buffer; + /* DMA channels */ #define DMA_CHANS 8 struct dma_chan *dma_chans[DMA_CHANS];
Brian