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

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

Hi Francesco,

francesco@dolcini.it wrote on Fri, 03 Feb 2023 19:03:27 +0100:

> Il 3 febbraio 2023 16:12:02 CET, Miquel Raynal <miquel.raynal@bootlin.com> ha scritto:
> >Hi Francesco,
> >
> >francesco@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@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@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>
> >> > > > > > ---
> >> > > > > > 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@33002000/partition@0 (/soc/nand-controller@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.

If this happens early next week I'll take the patch for my next PR.

> gpmi-nand: ofpart partition /soc/nand-controller@33002000/partition@0 (/soc/nand-controller@33002000) #size-cells is wrongly set to <0>, assuming <1> for parsing partitions.
> 
> Correct? Do you want a v5 with the reviewed-by greg removed or you remove it yourself?
> 
> Francesco
> 


Thanks,
Miquèl