[PATCH v4] mtd: parsers: ofpart: add workaround for #size-cells 0

[Greg Kroah-Hartman]

On Tue, Jan 24, 2023 at 11:44:44AM +0100, Francesco Dolcini wrote:
> From: Francesco Dolcini <francesco.dolcini at toradex.com>
> 
> Add a mechanism to handle the case in which partitions are present as
> direct child of the nand controller node and #size-cells is set to <0>.
> 
> This could happen if the nand-controller node in the DTS is supposed to
> have #size-cells set to 0, but for some historical reason/bug it was set
> to 1 in the past, and the firmware (e.g. U-Boot) is adding the partition
> as direct children of the nand-controller defaulting to #size-cells
> being to 1.
> 
> This prevents a real boot failure on colibri-imx7 that happened during v6.1
> development cycles.
> 
> Link: https://lore.kernel.org/all/Y4dgBTGNWpM6SQXI@francesco-nb.int.toradex.com/
> Link: https://lore.kernel.org/all/20221202071900.1143950-1-francesco@dolcini.it/
> Signed-off-by: Francesco Dolcini <francesco.dolcini at toradex.com>
> Reviewed-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
> ---
> I do not expect this patch to be backported to stable, however I would expect
> that we do not backport nand-controller dts cleanups neither.
> 
> v4:
>  fixed wrong English spelling in the comment
> 
> v3:
>  minor formatting change, removed not needed new-line and space. 
> 
> v2:
>  fixup size-cells only when partitions are direct children of the nand-controller
>  completely revised commit message, comments and warning print
>  use pr_warn instead of pr_warn_once
>  added Reviewed-by Greg
>  removed cc:stable@ and fixes tag, since the problematic commit was reverted
> ---
>  drivers/mtd/parsers/ofpart_core.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/drivers/mtd/parsers/ofpart_core.c b/drivers/mtd/parsers/ofpart_core.c
> index 192190c42fc8..e7b8e9d0a910 100644
> --- a/drivers/mtd/parsers/ofpart_core.c
> +++ b/drivers/mtd/parsers/ofpart_core.c
> @@ -122,6 +122,25 @@ static int parse_fixed_partitions(struct mtd_info *master,
>  
>  		a_cells = of_n_addr_cells(pp);
>  		s_cells = of_n_size_cells(pp);
> +		if (!dedicated && s_cells == 0) {
> +			/*
> +			 * This is a ugly workaround to not create
> +			 * regression on devices that are still creating
> +			 * partitions as direct children of the nand controller.
> +			 * This can happen in case the nand controller node has
> +			 * #size-cells equal to 0 and the firmware (e.g.
> +			 * U-Boot) just add the partitions there assuming
> +			 * 32-bit addressing.
> +			 *
> +			 * If you get this warning your firmware and/or DTS
> +			 * should be really fixed.
> +			 *
> +			 * This is working only for devices smaller than 4GiB.
> +			 */
> +			pr_warn("%s: ofpart partition %pOF (%pOF) #size-cells is wrongly set to <0>, assuming <1> for parsing partitions.\n",
> +				master->name, pp, mtd_node);

This is a driver, always use dev_*() calls, not pr_*() calls so that we
know what is being referred to exactly.

I take back my "reviewed-by" line above, please fix this up to not need
pr_warn, but to use dev_warn() instead.

thanks,

greg k-h