Hi Brian, On Thu, 20 Nov 2014 01:08:07 -0800 Brian Norris <[email protected]> wrote:
> On Mon, Oct 20, 2014 at 10:46:16AM +0200, Boris Brezillon wrote: > > 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 <[email protected]> > > --- > > 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. Sure, I'll add some comments. > > > +{ > > + 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? Actually, I call this function with a NULL buf in my 4th patch (to dump the oob area). > > > + 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"? AFAIR this is what the controller is doing (but I'll have to re-check that one). > > > + > > + oob_byte_off = DIV_ROUND_UP(oob_bit_off, 8); > > + > > + if (oob_byte_off < mtd->oobsize) > > Extra whitespace before '<'. I'll Fix that. Thanks for the review. Regards, Boris -- Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
