Boot failure regression on 6.0.10 stable kernel on iMX7

[Francesco Dolcini]

+ MTD maintainers/list

On Wed, Nov 30, 2022 at 11:59:04PM +0100, Marek Vasut wrote:
> On 11/30/22 21:51, Francesco Dolcini wrote:
> > On Wed, Nov 30, 2022 at 03:41:13PM +0100, Marek Vasut wrote:
> > > On 11/30/22 14:52, Francesco Dolcini wrote:
> > > > [    0.000000] Booting Linux on physical CPU 0x0
> > > > [    0.000000] Linux version 6.0.10 (francesco at francesco-nb) (arm-linux-gnueabihf-gcc (Ubuntu 9.4.0-1ubuntu1~20.04.1) 9.
> > > > 4.0, GNU ld (GNU Binutils for Ubuntu) 2.34) #36 SMP Wed Nov 30 14:07:15 CET 2022
> > > > ...
> > > > [    4.407499] gpmi-nand: error parsing ofpart partition /soc/nand-controller at 33002000/partition at 0 (/soc/nand-controller
> > > > @33002000)
> > > > [    4.438401] gpmi-nand 33002000.nand-controller: driver registered.
> > > > ...
> > > > [    5.933906] VFS: Cannot open root device "ubi0:rootfs" or unknown-block(0,0): error -19
> > > > [    5.946504] Please append a correct "root=" boot option; here are the available partitions:
> > > > ...
> > > > 
> > > > Any idea? I'm not familiar with the gpmi-nand driver and I would just revert it, but
> > > > maybe you have a better idea.
> > > 
> > > Can you share the relevant snippet of your nand controller DT node ?
> > 
> > We just have
> > 
> > from imx7-colibri.dtsi,
> > 
> >    &gpmi {
> >    	fsl,use-minimum-ecc;
> >    	nand-ecc-mode = "hw";
> >    	nand-on-flash-bbt;
> >    	pinctrl-names = "default";
> >    	pinctrl-0 = <&pinctrl_gpmi_nand>;
> >    };
> > 
> > OF partition are created by U-Boot from
> >    mtdparts=mtdparts=gpmi-nand:512k(mx7-bcb),1536k(u-boot1)ro,1536k(u-boot2)ro,512k(u-boot-env),-(ubi)
> > env variables calling fdt_fixup_mtdparts from colibri_imx7.c
> > 
> > Everything is available in the upstream Linux/U-Boot git, no downstream
> > repo of any sort.
> > 
> > > Probably up to first partition is enough. I suspect you need to fill in the
> > > correct address-cells/size-cells there, which might be currently missing in
> > > your DT and worked by chance.
> > 
> > This is generated by U-Boot, I would need to dump what he did generate
> > from the standard fdt_fixup_mtdparts(). I will try to do it tomorrow
> > unless what I wrote here is already enough to understand what's going
> > on.
> 
> Oh drat ... I see. It's the u-boot fdt_node_set_part_info() which checks the
> current NAND controller #size-cells and uses that when generating MTD
> partitions 'reg' properties. Since #size-cells is now zero, the reg
> properties would be malformed.

I think the issue is slightly different, the u-boot code checks it and
if not set it defaults to #size-cells = <1>. Said that u-boot
never set #size-cells anywhere.

What is failing is ofpart_core.c:parse_fixed_partitions() in Linux with
#size-cells = <0>.


> Now, what I am unsure is whether the right fix is to update mx7 colibri DT
> and include &gpmi { #size-cells=<1>; }; , or , revert this patch. The former
> fixes the problem for colibri and retains the correct #size-cells=<0>
> behavior for any other board which does not specify MTD partitions in the
> GPMI NAND node. The later also covers boards which we don't know about which
> might also use generated MTD partitions in DT using fdt_fixup_mtdparts() in
> U-Boot, but I am not convinced that is correct.
> 
> So, would you be OK with fixing up the colibri mx7 DT with #size-cells=<1> ?

I am also not sure what is the right fix, however I am convinced that
the fix needs to be in Linux, we cannot really break the boot flow.

In a very pragmatic way I could just add the property to colibri-imx7
dtsi, but we are really breaking potential other users of it, anybody
using U-Boot to generate the partitions in the end ... (and the list is
not empty and not just the colibri*).

Would it make any sense to do something like that (untested!) ?

diff --git a/drivers/mtd/parsers/ofpart_core.c b/drivers/mtd/parsers/ofpart_core.c
index 192190c42fc8..fffd60acd926 100644
--- a/drivers/mtd/parsers/ofpart_core.c
+++ b/drivers/mtd/parsers/ofpart_core.c
@@ -122,6 +122,8 @@ static int parse_fixed_partitions(struct mtd_info *master,

                a_cells = of_n_addr_cells(pp);
                s_cells = of_n_size_cells(pp);
+               if (s_cells == 0)
+                       s_cells = 1; // for backward compatibility
                if (len / 4 != a_cells + s_cells) {
                        pr_debug("%s: ofpart partition %pOF (%pOF) error parsing reg property.\n",
                                 master->name, pp,

Francesco