Re: [PATCH v2] mtd: parsers: ofpart: add workaround for #size-cells 0

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Francesco,

francesco@dolcini.it wrote on Fri, 13 Jan 2023 19:45:56 +0100:

> From: Francesco Dolcini <francesco.dolcini@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@toradex.com>
> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
> 
> Miquel, Marek: 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.

Okay.

> 
> 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 | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/drivers/mtd/parsers/ofpart_core.c b/drivers/mtd/parsers/ofpart_core.c
> index 192190c42fc8..46559a9248e6 100644
> --- a/drivers/mtd/parsers/ofpart_core.c
> +++ b/drivers/mtd/parsers/ofpart_core.c
> @@ -122,6 +122,26 @@ 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 hugly workaround to not create
> +			 * regression on devices that are still creating
> +			 * partitions as direct child 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);

Why mtd_node on a new line?

Otherwise looks good to me.

> +			s_cells = 1;
> +		}
>  		if (len / 4 != a_cells + s_cells) {
>  			pr_debug("%s: ofpart partition %pOF (%pOF) error parsing reg property.\n",
>  				 master->name, pp,


Thanks,
Miquèl