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

From: Vladimir Murzin <vladimir.murzin@arm.com>
To: Andre Przywara <andre.przywara@arm.com>,
	Mark Rutland <mark.rutland@arm.com>
Cc: 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 18:42:50 +0000	[thread overview]
Message-ID: <706471d8-a0fd-35fb-4fa0-380bfb1b78e7@arm.com> (raw)
In-Reply-To: <20211222181607.1203191-10-andre.przywara@arm.com>

Hi Andre,

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

FATAL ERROR: Unrecognized check name "clocks_property"

Cheers
Vladimir

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