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SubjectRe: [PATCH 7/9] mtd: nand: qcom: check for operation errors in case of raw read
Hi Abhishek,

On Wed, 4 Apr 2018 18:12:23 +0530, Abhishek Sahu
<absahu@codeaurora.org> wrote:

> Currently there is no error checking for raw read. For raw
> reads, there won’t be any ECC failure but the operational
> failures are possible so schedule the NAND_FLASH_STATUS read
> after each codeword.
>
> Signed-off-by: Abhishek Sahu <absahu@codeaurora.org>
> ---
> drivers/mtd/nand/qcom_nandc.c | 56 +++++++++++++++++++++++++++++++++++--------
> 1 file changed, 46 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/mtd/nand/qcom_nandc.c b/drivers/mtd/nand/qcom_nandc.c
> index dce97e8..40c790e 100644
> --- a/drivers/mtd/nand/qcom_nandc.c
> +++ b/drivers/mtd/nand/qcom_nandc.c
> @@ -1099,7 +1099,8 @@ static void config_nand_page_read(struct qcom_nand_controller *nandc)
> * Helper to prepare DMA descriptors for configuring registers
> * before reading each codeword in NAND page.
> */
> -static void config_nand_cw_read(struct qcom_nand_controller *nandc)
> +static void
> +config_nand_cw_read(struct qcom_nand_controller *nandc, bool use_ecc)
> {
> if (nandc->props->is_bam)
> write_reg_dma(nandc, NAND_READ_LOCATION_0, 4,
> @@ -1108,19 +1109,25 @@ static void config_nand_cw_read(struct qcom_nand_controller *nandc)
> write_reg_dma(nandc, NAND_FLASH_CMD, 1, NAND_BAM_NEXT_SGL);
> write_reg_dma(nandc, NAND_EXEC_CMD, 1, NAND_BAM_NEXT_SGL);
>
> - read_reg_dma(nandc, NAND_FLASH_STATUS, 2, 0);
> - read_reg_dma(nandc, NAND_ERASED_CW_DETECT_STATUS, 1,
> - NAND_BAM_NEXT_SGL);
> + if (use_ecc) {
> + read_reg_dma(nandc, NAND_FLASH_STATUS, 2, 0);
> + read_reg_dma(nandc, NAND_ERASED_CW_DETECT_STATUS, 1,
> + NAND_BAM_NEXT_SGL);
> + } else {
> + read_reg_dma(nandc, NAND_FLASH_STATUS, 1, NAND_BAM_NEXT_SGL);
> + }
> }
>
> /*
> * Helper to prepare dma descriptors to configure registers needed for reading a
> * single codeword in page
> */
> -static void config_nand_single_cw_page_read(struct qcom_nand_controller *nandc)
> +static void
> +config_nand_single_cw_page_read(struct qcom_nand_controller *nandc,
> + bool use_ecc)
> {
> config_nand_page_read(nandc);
> - config_nand_cw_read(nandc);
> + config_nand_cw_read(nandc, use_ecc);
> }
>
> /*
> @@ -1201,7 +1208,7 @@ static int nandc_param(struct qcom_nand_host *host)
> nandc->buf_count = 512;
> memset(nandc->data_buffer, 0xff, nandc->buf_count);
>
> - config_nand_single_cw_page_read(nandc);
> + config_nand_single_cw_page_read(nandc, false);
>
> read_data_dma(nandc, FLASH_BUF_ACC, nandc->data_buffer,
> nandc->buf_count, 0);
> @@ -1565,6 +1572,23 @@ struct read_stats {
> __le32 erased_cw;
> };
>
> +/* reads back FLASH_STATUS register set by the controller */
> +static int check_flash_errors(struct qcom_nand_host *host, int cw_cnt)
> +{
> + struct nand_chip *chip = &host->chip;
> + struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
> + int i;
> +
> + for (i = 0; i < cw_cnt; i++) {
> + u32 flash = le32_to_cpu(nandc->reg_read_buf[i]);
> +
> + if (flash & (FS_OP_ERR | FS_MPU_ERR))
> + return -EIO;

This is already checked in parse_read_error(), maybe it would be
preferable to have different path inside this function depending on the
'raw' nature of the operation?

> + }
> +
> + return 0;
> +}
> +
> /*
> * reads back status registers set by the controller to notify page read
> * errors. this is equivalent to what 'ecc->correct()' would do.
> @@ -1707,7 +1731,7 @@ static int read_page_ecc(struct qcom_nand_host *host, u8 *data_buf,
> }
> }
>
> - config_nand_cw_read(nandc);
> + config_nand_cw_read(nandc, true);
>
> if (data_buf)
> read_data_dma(nandc, FLASH_BUF_ACC, data_buf,
> @@ -1771,7 +1795,7 @@ static int copy_last_cw(struct qcom_nand_host *host, int page)
> set_address(host, host->cw_size * (ecc->steps - 1), page);
> update_rw_regs(host, 1, true);
>
> - config_nand_single_cw_page_read(nandc);
> + config_nand_single_cw_page_read(nandc, host->use_ecc);
>
> read_data_dma(nandc, FLASH_BUF_ACC, nandc->data_buffer, size, 0);
>
> @@ -1781,6 +1805,15 @@ static int copy_last_cw(struct qcom_nand_host *host, int page)
>
> free_descs(nandc);
>
> + if (!ret) {
> + if (host->use_ecc)
> + ret = parse_read_errors(host, nandc->data_buffer,
> + nandc->data_buffer + size,
> + true);
> + else
> + ret = check_flash_errors(host, 1);

This way you would avoid this ^

> + }
> +

As a general way, I don't like very much this kind of error checking
structure:

if (!ret)
ret = something();
...
return ret;

I would rather prefer:

if (ret)
return ret;

return something();

> return ret;
> }
>
> @@ -1854,7 +1887,7 @@ static int qcom_nandc_read_page_raw(struct mtd_info *mtd,
> nandc_set_read_loc(nandc, 3, read_loc, oob_size2, 1);
> }
>
> - config_nand_cw_read(nandc);
> + config_nand_cw_read(nandc, false);
>
> read_data_dma(nandc, reg_off, data_buf, data_size1, 0);
> reg_off += data_size1;
> @@ -1878,6 +1911,9 @@ static int qcom_nandc_read_page_raw(struct mtd_info *mtd,
>
> free_descs(nandc);
>
> + if (!ret)
> + ret = check_flash_errors(host, ecc->steps);
> +

There is not point in doing ret = ... if you return 0 right after.
Please check what would be the most appropriate.

> return 0;
> }
>

Thanks,
Miquèl

--
Miquel Raynal, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com
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