Re: [PATCH 5/8] mtd: nand: mxc: Fix failed/corrected values for v1 controllers

Boris Brezillon
2018-01-12T15:29:13Z

On Tue, 9 Jan 2018 11:11:45 +0100
Sascha Hauer <s.hauer@pengutronix.de> wrote:

> The v1 controller code has several flaws:
> - We do not forward the number of corrected bitflips to the upper layers
> - For 2k page NAND chips only the status results from the fourth subpage
> read are evaluated, so ECC failures in the other subpages remain
> uncovered
> - When there are uncorrectable errors we have to increase the statistics
> counter, but still have to return successfully. Currently we return
> an error
>
> This patch fixes this by introducing a v1 specific read_page function.
>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
> drivers/mtd/nand/mxc_nand.c | 78 +++++++++++++++++++++++++++++++++++----------
> 1 file changed, 62 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/mtd/nand/mxc_nand.c b/drivers/mtd/nand/mxc_nand.c
> index d698f7c6666c..83bb01ab7079 100644
> --- a/drivers/mtd/nand/mxc_nand.c
> +++ b/drivers/mtd/nand/mxc_nand.c
> @@ -738,22 +738,68 @@ static void mxc_nand_enable_hwecc(struct mtd_info *mtd, int mode)
> static int mxc_nand_correct_data_v1(struct mtd_info *mtd, u_char *dat,
> u_char *read_ecc, u_char *calc_ecc)
> {
> + return 0;
> +}
> +
> +static int mxc_nand_read_page_v1(struct mtd_info *mtd, struct nand_chip *chip,
> + void *buf, void *oob, bool ecc, int page)
> +{
> struct nand_chip *nand_chip = mtd_to_nand(mtd);
> - struct mxc_nand_host *host = nand_get_controller_data(nand_chip);
> + struct mxc_nand_host *host = nand_get_controller_data(chip);
> + unsigned int max_bitflips = 0;
> + int no_subpages;
> + int i;
>
> - /*
> - * 1-Bit errors are automatically corrected in HW. No need for
> - * additional correction. 2-Bit errors cannot be corrected by
> - * HW ECC, so we need to return failure
> - */
> - uint16_t ecc_status = get_ecc_status_v1(host);
> + host->devtype_data->enable_hwecc(nand_chip, ecc);
> +
> + host->devtype_data->send_cmd(host, NAND_CMD_READ0, false);
> + mxc_do_addr_cycle(mtd, 0, page);
> +
> + if (mtd->writesize > 512)
> + host->devtype_data->send_cmd(host, NAND_CMD_READSTART, true);
>
> - if (((ecc_status & 0x3) == 2) || ((ecc_status >> 2) == 2)) {
> - dev_dbg(host->dev, "HWECC uncorrectable 2-bit ECC error\n");
> - return -EBADMSG;
> + no_subpages = mtd->writesize >> 9;
> +
> + for (i = 0; i < no_subpages; i++) {
> + int flips = 0;
> + uint16_t ecc_stats;
> +
> + /* NANDFC buffer 0 is used for page read/write */
> + writew((host->active_cs << 4) | i, NFC_V1_V2_BUF_ADDR);
> +
> + writew(NFC_OUTPUT, NFC_V1_V2_CONFIG2);
> +
> + /* Wait for operation to complete */
> + wait_op_done(host, true);
> +
> + ecc_stats = get_ecc_status_v1(host);
> +
> + ecc_stats >>= 2;
> +
> + if (buf && ecc) {
> + switch (ecc_stats & 0x3) {
> + case 0:
> + default:
> + break;
> + case 1:
> + mtd->ecc_stats.corrected++;
> + flips++;

Since the engine is anyway able to correct a maximum of 1 bitflip you
can get rid of flips and do:

max_bitflips = 1;

You could even rename max_bitflips into bitflips_corrected.

> + break;
> + case 2:
> + mtd->ecc_stats.failed++;
> + break;
> + }
> + }
> +
> + max_bitflips = max_t(unsigned int, max_bitflips, flips);

If you get rid of flips, this is not needed.

> }
>
> - return 0;
> + if (buf)
> + memcpy32_fromio(buf, host->main_area0, mtd->writesize);
> + if (oob)
> + copy_spare(mtd, true, oob);
> +
> + return max_bitflips;
> }
>
> static int mxc_nand_correct_data_v2_v3(struct mtd_info *mtd, u_char *dat,
> @@ -1494,6 +1540,7 @@ static struct nand_bbt_descr bbt_mirror_descr = {
> /* v1 + irqpending_quirk: i.MX21 */
> static const struct mxc_nand_devtype_data imx21_nand_devtype_data = {
> .preset = preset_v1,
> + .read_page = mxc_nand_read_page_v1,
> .send_cmd = send_cmd_v1_v2,
> .send_addr = send_addr_v1_v2,
> .send_page = send_page_v1,
> @@ -1518,6 +1565,7 @@ static const struct mxc_nand_devtype_data imx21_nand_devtype_data = {
> /* v1 + !irqpending_quirk: i.MX27, i.MX31 */
> static const struct mxc_nand_devtype_data imx27_nand_devtype_data = {
> .preset = preset_v1,
> + .read_page = mxc_nand_read_page_v1,
> .send_cmd = send_cmd_v1_v2,
> .send_addr = send_addr_v1_v2,
> .send_page = send_page_v1,
> @@ -1856,11 +1904,9 @@ static int mxcnd_probe(struct platform_device *pdev)
>
> switch (this->ecc.mode) {
> case NAND_ECC_HW:
> - if (host->devtype_data->read_page) {
> - this->ecc.read_page = mxc_nand_read_page;
> - this->ecc.read_page_raw = mxc_nand_read_page_raw;
> - this->ecc.read_oob = mxc_nand_read_oob;
> - }
> + this->ecc.read_page = mxc_nand_read_page;
> + this->ecc.read_page_raw = mxc_nand_read_page_raw;
> + this->ecc.read_oob = mxc_nand_read_oob;
> this->ecc.calculate = mxc_nand_calculate_ecc;
> this->ecc.hwctl = mxc_nand_enable_hwecc;
> this->ecc.correct = host->devtype_data->correct_data;