linux-kernel - Re: [PATCH 3/4] arm64: dts: exynos: make tm2 and tm2e independent from each other

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Date:   Wed, 4 Jan 2017 00:29:23 +0900
From:   Chanwoo Choi <cwchoi00@...il.com>
To:     Andi Shyti <andi@...zian.org>
Cc:     Javier Martinez Canillas <javier@....samsung.com>,
        Andi Shyti <andi.shyti@...sung.com>,
        Mark Rutland <mark.rutland@....com>,
        devicetree <devicetree@...r.kernel.org>,
        linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Jaechul Lee <jcsing.lee@...sung.com>,
        Will Deacon <will.deacon@....com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Rob Herring <robh+dt@...nel.org>,
        Kukjin Kim <kgene@...nel.org>, linux-input@...r.kernel.org,
        galaxyra@...il.com, beomho.seo@...sung.com,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 3/4] arm64: dts: exynos: make tm2 and tm2e independent
 from each other

Hi Andi,

2017-01-03 23:40 GMT+09:00 Andi Shyti <andi@...zian.org>:
> Hi,
>
>> FWIW, I also agree with Chanwoo that the difference is too small to
>> need a common .dtsi file.
>
> in principle I don't like "switching on and off" properties by
> overwriting them with "status = disable", unless it's really
> necessary (and this case is not). Even for small differences. It
> makes the DTS harder to read and duplicates nodes with different
> values throughout the DTS include chain.
>
> In my opinion this approach should be discouraged.
>
> Besides, there are other overwritten differences in tm2e.dts that
> I think should be separated as well. The "common" file approach is
> widely used in arm/boot/dts/exynos* files.
>
> The "status = disable" looks to me more like a temporary hack
> rather than a permanent solution.
>
> In any case, still up to you :)
>
> Andi

I think that "status=disabled" of hsi2c_9 is not hack. The overwrite
is possible for Device-tree. But, there is just difference how to
support them with some method.

Except for touchkey, all peripheral device are same on both tm2 and
tm2e. There are only small difference for a few property value.

To understand the difference between tm2 and tm2e, I made the patch
(it is not complete version). If we implement the following patch, we
support both tm2 and tm2e. So, I think that it is not complex to
understand the h/w difference between tm2 and tm2e.

diff --git a/arch/arm64/boot/dts/exynos/exynos5433-tm2e.dts
b/arch/arm64/boot/dts/exynos/exynos5433-tm2e.dts
index 1db4e7f..09b6935 100644
--- a/arch/arm64/boot/dts/exynos/exynos5433-tm2e.dts
+++ b/arch/arm64/boot/dts/exynos/exynos5433-tm2e.dts
@@ -18,6 +18,17 @@
        compatible = "samsung,tm2e", "samsung,exynos5433";
 };

+&display_timings {
+       clock-frequency = <16523724>;
+       hactive = <1600>;
+};
+
+&hsi2c_9 {
+        /* TM2E don't use the separate touchkey device. Instead, touchscreen
+         * device support the touchkey device.*/
+       status = "disabled";
+};
+
 &ldo23_reg {
        regulator-name = "CAM_SEN_CORE_1.025V_AP";
        regulator-max-microvolt = <1050000>;
@@ -39,3 +50,7 @@
        regulator-min-microvolt = <3300000>;
        regulator-max-microvolt = <3300000>;
 };
+
+&touchscreen {
+       x-size = "1599";
+};

-- 
Best Regards,
Chanwoo Choi