Re: [boot-wrapper PATCH v2 9/9] avoid dtc warnings on re-compiling DTB

From: Andre Przywara <andre.przywara@arm.com>
To: Vladimir Murzin <vladimir.murzin@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	Jaxson Han <jaxson.han@arm.com>
Subject: Re: [boot-wrapper PATCH v2 9/9] avoid dtc warnings on re-compiling DTB
Date: Thu, 13 Jan 2022 19:50:51 +0000	[thread overview]
Message-ID: <20220113195051.7100b066@slackpad.fritz.box> (raw)
In-Reply-To: <706471d8-a0fd-35fb-4fa0-380bfb1b78e7@arm.com>

On Thu, 13 Jan 2022 18:42:50 +0000
Vladimir Murzin <vladimir.murzin@arm.com> wrote:

Hi Vladimir,

> On 12/22/21 6:16 PM, Andre Przywara wrote:
> > When we add the PSCI nodes to the provided DTB, we use dtc to de-compile
> > the blob first, then re-compile it with our nodes and properties added.
> > 
> > In our input DTB the proper phandle references have already been lost,
> > all we see in the DTB is phandle properties in the target node, and some
> > numbers in the clocks and gpios properties:
> > ===========
> > 	clk24mhz {
> > 		compatible = "fixed-clock";
> > 		#clock-cells = <0x00>;
> > 		clock-frequency = <0x16e3600>;
> > 		clock-output-names = "v2m:clk24mhz";  
> > ->		phandle = <0x05>;  
> > 	};
> > 	...
> > 	serial@90000 {
> > 		compatible = "arm,pl011", "arm,primecell";
> > 		reg = <0x90000 0x1000>;
> > 		interrupts = <0x05>;  
> > ->		clocks = <0x05 0x05>;  
> > 		clock-names = "uartclk", "apb_pclk";
> > 	};
> > ===========
> > dtc warns that those numbers might be wrong:
> > =========
> > <stdin>:177.6-27: Warning (clocks_property):
> >  /bus@8000000/motherboard-bus@8000000/iofpga-bus@300000000/serial@90000:
> >    clocks: cell 0 is not a phandle reference
> > ....
> > =========
> > The proper solution would be to use references (&v2m_clk24mhz) instead,
> > as there are in the source .dts file, but we don't have that information
> > anymore, and cannot easily recover it.
> > 
> > To avoid the lengthy list of warnings, just drop those checks from the
> > dtc compilation run. This disables more checks than we want or need, but
> > we somewhat trust in the original DTB to be sane, so that should be
> > fine.
> > 
> > Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> > ---
> >  Makefile.am | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/Makefile.am b/Makefile.am
> > index 3d8128f..430b4a9 100644
> > --- a/Makefile.am
> > +++ b/Makefile.am
> > @@ -160,7 +160,7 @@ model.lds: $(LD_SCRIPT) Makefile
> >  	$(CPP) $(CPPFLAGS) -ansi -DPHYS_OFFSET=$(PHYS_OFFSET) -DMBOX_OFFSET=$(MBOX_OFFSET) -DKERNEL_OFFSET=$(KERNEL_OFFSET) -DFDT_OFFSET=$(FDT_OFFSET) -DFS_OFFSET=$(FS_OFFSET) $(XEN) -DXEN_OFFSET=$(XEN_OFFSET) -DKERNEL=$(KERNEL_IMAGE) -DFILESYSTEM=$(FILESYSTEM) -DTEXT_LIMIT=$(TEXT_LIMIT) -P -C -o $@ $<
> >  
> >  fdt.dtb: $(KERNEL_DTB) Makefile
> > -	( $(DTC) -O dts -I dtb $(KERNEL_DTB) ; echo "/ { $(CHOSEN_NODE) $(PSCI_NODE) }; $(CPU_NODES)" ) | $(DTC) -O dtb -o $@ -
> > +	( $(DTC) -O dts -I dtb $(KERNEL_DTB) ; echo "/ { $(CHOSEN_NODE) $(PSCI_NODE) }; $(CPU_NODES)" ) | $(DTC) -O dtb -o $@ -Wno-clocks_property -Wno-gpios_property -
> >  
> >  # The filesystem archive might not exist if INITRD is not being used
> >  .PHONY: all clean $(FILESYSTEM)
> >   
> 
> dtc 1.4.1 complains

Which distro ships this version? (distrowatch doesn't list dtc)

tag v1.4.1
Tagger: David Gibson <david@gibson.dropbear.id.au>
Date:   Wed Nov 12 14:31:44 2014 +1100

Any chance it's just you and you can update this? It looks like the
first version to support it is 1.4.5, as shipped for instance with
Ubuntu 18.04.

> FATAL ERROR: Unrecognized check name "clocks_property"

Sigh, thanks for the heads up. I don't know if we want to blow up the
Makefile with a feature test?

Cheers,
Andre

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