Re: [PATCH 01/13] mtd: nand: fsmc: fix NAND width handling

Boris Brezillon
2017-03-22T21:43:03Z

+Greg for the backport to stable question.

On Tue, 21 Mar 2017 11:03:53 +0100
Thomas Petazzoni <thomas.petazzoni@free-electrons.com> wrote:

> In commit eea628199d5b ("mtd: Add device-tree support to fsmc_nand"),
> Device Tree support was added to the fmsc_nand driver. However, this
> code has a bug in how it handles the bank-width DT property to set the
> bus width.
>
> Indeed, in the function fsmc_nand_probe_config_dt() that parses the
> Device Tree, it sets pdata->width to either 8 or 16 depending on the
> value of the bank-width DT property.
>
> Then, the ->probe() function will test if pdata->width is equal to
> FSMC_NAND_BW16 (which is 2) to set NAND_BUSWIDTH_16 in
> nand->options. Therefore, with the DT probing, this condition will never
> match.
>
> This commit fixes that by removing the "width" field from
> fsmc_nand_platform_data and instead have the fsmc_nand_probe_config_dt()
> function directly set the appropriate nand->options value.
>
> It is worth mentioning that if this commit gets backported to older
> kernels, prior to the drop of non-DT probing, then non-DT probing will
> be broken because nand->options will no longer be set to
> NAND_BUSWIDTH_16.

Then maybe we should the drop the Cc-stable tag, or put # vX.Y+ to
prevent this patch from being applied to versions where it could break
things.

Note that no-one complained about this bug so far, so I guess no-one
cares about this fix (probably because 16-bits NANDs are not widely
used) ;-).

>
> Fixes: eea628199d5b ("mtd: Add device-tree support to fsmc_nand")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
> ---
> drivers/mtd/nand/fsmc_nand.c | 13 +++++--------
> 1 file changed, 5 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/mtd/nand/fsmc_nand.c b/drivers/mtd/nand/fsmc_nand.c
> index bda1e46..66aece9 100644
> --- a/drivers/mtd/nand/fsmc_nand.c
> +++ b/drivers/mtd/nand/fsmc_nand.c
> @@ -150,7 +150,6 @@ struct fsmc_nand_platform_data {
> struct mtd_partition *partitions;
> unsigned int nr_partitions;
> unsigned int options;
> - unsigned int width;
> unsigned int bank;
>
> enum access_mode mode;
> @@ -844,18 +843,19 @@ static int fsmc_nand_probe_config_dt(struct platform_device *pdev,
> u32 val;
> int ret;
>
> - /* Set default NAND width to 8 bits */
> - pdata->width = 8;
> + pdata->options = 0;
> +
> if (!of_property_read_u32(np, "bank-width", &val)) {
> if (val == 2) {
> - pdata->width = 16;
> + pdata->options |= NAND_BUSWIDTH_16;
> } else if (val != 1) {
> dev_err(&pdev->dev, "invalid bank-width %u\n", val);
> return -EINVAL;
> }
> }
> +
> if (of_get_property(np, "nand-skip-bbtscan", NULL))
> - pdata->options = NAND_SKIP_BBTSCAN;
> + pdata->options |= NAND_SKIP_BBTSCAN;
>
> pdata->nand_timings = devm_kzalloc(&pdev->dev,
> sizeof(*pdata->nand_timings), GFP_KERNEL);
> @@ -992,9 +992,6 @@ static int __init fsmc_nand_probe(struct platform_device *pdev)
> nand->badblockbits = 7;
> nand_set_flash_node(nand, np);
>
> - if (pdata->width == FSMC_NAND_BW16)
> - nand->options |= NAND_BUSWIDTH_16;
> -
> switch (host->mode) {
> case USE_DMA_ACCESS:
> dma_cap_zero(mask);