[PATCH v4] mtd: parsers: ofpart: add workaround for #size-cells 0
Francesco Dolcini
francesco at dolcini.it
Fri Feb 3 19:37:03 CET 2023
Il 3 febbraio 2023 19:16:23 CET, Miquel Raynal <miquel.raynal at bootlin.com> ha scritto:
>Hi Francesco,
>
>francesco at dolcini.it wrote on Fri, 03 Feb 2023 19:03:27 +0100:
>
>> Il 3 febbraio 2023 16:12:02 CET, Miquel Raynal <miquel.raynal at bootlin.com> ha scritto:
>> >Hi Francesco,
>> >
>> >francesco at dolcini.it wrote on Thu, 2 Feb 2023 12:33:34 +0100:
>> >
>> >> On Thu, Jan 26, 2023 at 10:12:04AM +0100, Miquel Raynal wrote:
>> >> > gregkh at linuxfoundation.org wrote on Thu, 26 Jan 2023 10:01:02 +0100:
>> >> >
>> >> > > On Wed, Jan 25, 2023 at 10:06:57PM +0100, Francesco Dolcini wrote:
>> >> > > > Hello Miquel, Greg and all
>> >> > > >
>> >> > > > On Tue, Jan 24, 2023 at 04:38:59PM +0100, Greg Kroah-Hartman wrote:
>> >> > > > > 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.
>> >> > > >
>> >> > > > Is this reasonable here? Where can I get the struct device?
>> >> > >
>> >> > > Walk back up the call chain, there has to be a device somewhere
>> >> > > controlling this, right?
>> >> > >
>> >> > > > In general this file uses only pr_* debug API and messages are about OF
>> >> > > > nodes/properties, not about a device.
>> >> > >
>> >> > > OF nodes and properties are part of a device's properties :)
>> >> >
>> >> > Yes but the warning comes from a wrong DT description, hence it felt
>> >> > better suited to warn against the node name which is easily identifiable
>> >> > in a text file and must be fixed rather than the device which is a pure
>> >> > software component.
>> >> >
>> >> > Anyway, Francesco, please show us the resultant line and if it feels
>> >> > meaningful enough we'll take the dev_warn approach.
>> >>
>> >> So, I tried, but I guess I failed.
>> >>
>> >> Both
>> >>
>> >> dev_warn(&mtd_get_master(master)->dev, ...);
>> >>
>> >> and
>> >>
>> >> dev_warn(&master->dev, ...);
>> >>
>> >> are NULL.
>> >
>> >mtd->dev (in raw NAND) is populated by the controller drivers, so the
>> >master mtd device is pointing to the bus "struct device" in its
>> >dev.parent field. This happens at the end of the probe of the
>> >controller, after setting the dev entry, so we expect the name of the
>> >controller to appear.
>> >
>> >> (null): gpmi-nand: ofpart partition /soc/nand-controller at 33002000/partition at 0 (/soc/nand-controller at 33002000) #size-cells is wrongly set to <0>, assuming <1> for parsing partitions.
>> >
>> >Second field looks right, first field does not (bus or class id?) I
>> >have no idea why it has not been populated at this point (end of the
>> >controller probe). But it's not a big deal, at least we have the device
>> >name, so it's ok for me.
>>
>> If I understand correctly you are fine with the current patch v4 that just print (on colibri-imx7)
>
>Well, yes I was fine with it, but no that's not what I meant.
>
>AFAIS, using dev_warn() starts with "(null): gpmi-nand:" while pr_warn
>started with "gpmi-nand:", so for me the main and relevant information
>is present, that's all what I care about.
>
>Greg cared about the API used so I believe he would prefer us to use
>dev_warn().
>
>It is unusual to apply a patch on which someone active in the community
>answered negatively as long as his concerns can be addressed, so I
>would like Greg to either state that he is fine with the pr_warn or you
>to send a v5 using dev_warn() and him to send his R-by back.
Perfect, I understand and agree.
I was somehow puzzled because changing to dev_warn() on this specific warning message while the whole file already uses pr_warn() just to get a "(null):" prefix in the logs seems a little pointless to me.
Francesco
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