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Date:   Thu, 26 Apr 2018 00:01:49 +0200
From:   Alexandre Belloni <alexandre.belloni@bootlin.com>
To:     James Hogan <jhogan@kernel.org>, Ralf Baechle <ralf@linux-mips.org>
Cc:     Allan Nielsen <Allan.Nielsen@microsemi.com>,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
        linux-mips@linux-mips.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] mips: generic: allow not building DTB in
Message-ID: <20180425220149.GI4813@piout.net>
References: <20180425211607.2645-1-alexandre.belloni@bootlin.com>
 <20180425211607.2645-2-alexandre.belloni@bootlin.com>
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Hi,

On 25/04/2018 23:16:07+0200, Alexandre Belloni wrote:
> Allow not building any DTB in the generic kernel so it gets smaller. This
> is necessary for ocelot because it can be built as a legacy platform that
> needs a built-in DTB and it can also handle a separate DTB once it is
> updated with a more modern bootloader. In the latter case, it is preferable
> to not include any DTB in the kernel image so it is smaller.
> 
> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
> ---
>  arch/mips/Kconfig                | 1 -
>  arch/mips/Makefile               | 2 +-
>  arch/mips/boot/dts/mscc/Makefile | 2 +-
>  arch/mips/generic/Kconfig        | 1 +
>  arch/mips/generic/vmlinux.its.S  | 2 ++
>  5 files changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index 225c95da23ce..61057761d096 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -81,7 +81,6 @@ choice
>  config MIPS_GENERIC
>  	bool "Generic board-agnostic MIPS kernel"
>  	select BOOT_RAW
> -	select BUILTIN_DTB
>  	select CEVT_R4K
>  	select CLKSRC_MIPS_GIC
>  	select COMMON_CLK
> diff --git a/arch/mips/Makefile b/arch/mips/Makefile
> index 5e9fce076ab6..3d3554c13710 100644
> --- a/arch/mips/Makefile
> +++ b/arch/mips/Makefile
> @@ -404,7 +404,7 @@ endif
>  CLEAN_FILES += vmlinux.32 vmlinux.64
>  
>  # device-trees
> -core-$(CONFIG_BUILTIN_DTB) += arch/mips/boot/dts/
> +core-y += arch/mips/boot/dts/
>  
>  %.dtb %.dtb.S %.dtb.o: | scripts
>  	$(Q)$(MAKE) $(build)=arch/mips/boot/dts arch/mips/boot/dts/$@
> diff --git a/arch/mips/boot/dts/mscc/Makefile b/arch/mips/boot/dts/mscc/Makefile
> index 8982b19504a3..437ec65ec14a 100644
> --- a/arch/mips/boot/dts/mscc/Makefile
> +++ b/arch/mips/boot/dts/mscc/Makefile
> @@ -1,3 +1,3 @@
>  dtb-$(CONFIG_MSCC_OCELOT)	+= ocelot_pcb123.dtb
>  
> -obj-y				+= $(patsubst %.dtb, %.dtb.o, $(dtb-y))
> +obj-($CONFIG_BUILTIN_DTB)	+= $(patsubst %.dtb, %.dtb.o, $(dtb-y))

I made a typo here, I'll resend after waiting for a few comments.

> diff --git a/arch/mips/generic/Kconfig b/arch/mips/generic/Kconfig
> index 6564f18b2012..012f283f99c4 100644
> --- a/arch/mips/generic/Kconfig
> +++ b/arch/mips/generic/Kconfig
> @@ -3,6 +3,7 @@ if MIPS_GENERIC
>  
>  config LEGACY_BOARDS
>  	bool
> +	select BUILTIN_DTB
>  	help
>  	  Select this from your board if the board must use a legacy, non-UHI,
>  	  boot protocol. This will cause the kernel to scan through the list of
> diff --git a/arch/mips/generic/vmlinux.its.S b/arch/mips/generic/vmlinux.its.S
> index 1a08438fd893..9c954f2ae561 100644
> --- a/arch/mips/generic/vmlinux.its.S
> +++ b/arch/mips/generic/vmlinux.its.S
> @@ -21,6 +21,7 @@
>  		};
>  	};
>  
> +#if IS_ENABLED(CONFIG_BUILTIN_DTB)
>  	configurations {
>  		default = "conf@default";
>  
> @@ -29,4 +30,5 @@
>  			kernel = "kernel@0";
>  		};
>  	};
> +#endif
>  };
> -- 
> 2.17.0
> 

-- 
Alexandre Belloni, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com