linux-kernel - Re: [PATCH] ARM: dts: Add Exynos5250 Snow Rev5+ support

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Message-id: <560B2D29.5060707@samsung.com>
Date:	Wed, 30 Sep 2015 09:30:33 +0900
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Javier Martinez Canillas <javier@....samsung.com>,
	linux-kernel@...r.kernel.org
Cc:	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Doug Anderson <dianders@...omium.org>,
	Olof Johansson <olof@...om.net>,
	Russell King <linux@....linux.org.uk>,
	Kukjin Kim <kgene@...nel.org>, devicetree@...r.kernel.org,
	Kumar Gala <galak@...eaurora.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	linux-samsung-soc@...r.kernel.org,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: dts: Add Exynos5250 Snow Rev5+ support

On 29.09.2015 20:57, Javier Martinez Canillas wrote:
> There are 2 revisions of the Exynos5250 Snow Chromebook that were shipped:
> Rev4 and Rev5. The only difference between these 2 revisions is the codec,
> Rev4 has a max98095 codec while Rev5 has a max98090.
> 
> Mainline only supports Rev4 so this patch moves the common device nodes to
> a DTSI file and adds a DTS for the Exynos5250 Snow Rev5.
> 
> The Snow Rev5 DTS is based on the DTS found in the ChromiumOS 3.8 tree.
> 
> Signed-off-by: Javier Martinez Canillas <javier@....samsung.com>
> 
> ---
> 
> The DTS in the vendor ChromeOS tree are called exynos5250-snow-rev{4,5}.dtb
> but I decided to leave Rev4 as exynos5250-snow.dtb to avoid breaking u-boot
> that has CONFIG_DEFAULT_DEVICE_TREE="exynos5250-snow" in snow_defconfig.
> 
> Also, ChromiumOS Rev4 DTS has "google,snow-rev4" in its compatible string
> but was not added in mainline since Rev4 firmware fallbacks to "google,snow"
> and Rev5 searches for "google,snow-rev5". That way the compatible string
> could be consistent with the DTS naming and still be able to pack both Rev4
> and Rev5 FDT in the same FIT image and let the firmware pick the correct FDT.
> 
>  arch/arm/boot/dts/Makefile                    |   1 +
>  arch/arm/boot/dts/exynos5250-snow-common.dtsi | 684 ++++++++++++++++++++++++++
>  arch/arm/boot/dts/exynos5250-snow-rev5.dts    |  47 ++
>  arch/arm/boot/dts/exynos5250-snow.dts         | 666 +------------------------
>  4 files changed, 733 insertions(+), 665 deletions(-)
>  create mode 100644 arch/arm/boot/dts/exynos5250-snow-common.dtsi
>  create mode 100644 arch/arm/boot/dts/exynos5250-snow-rev5.dts

Now the exynos5250-snow.dts means in fact Rev4... but there is no
information in DTS about it. I think adding compatible
"google,snow-rev4" makes sense:
1. For informational purposes (this could be also handled with a comment).
2. Later one could decide to switch the default meaning of "google,snow"
to Rev5 and the real compatible (rev4) will be there already.

Could you add the new compatible and fix patch issues pointed by Doug?

Best regards,
Krzysztof

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