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

[Mark Rutland <mark.rutland@arm.com>]

On Fri, Jan 14, 2022 at 08:35:06AM +0000, Vladimir Murzin wrote:
> Hi Andre,
> 
> On 1/13/22 7:50 PM, Andre Przywara wrote:
> > 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.
> 
> It is shipped as LSF module. I can try to ask for an update, but I thought
> that other people may run into it as well...
> 
> > 
> >> 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?
> 
> I dunno, TBH. It look like warning used to be less evil than error...

I agree.

My preference would be to revert that for now, and consider the problem afresh.
Andre, are you ok with that?

Mark.

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