linux-kernel - Re: [PATCH v7 3/4] drm/panel: Add support for S6E3HA2 panel driver on TM2 board

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Message-id: <5df95abe-0d5d-0c48-2840-5996260201de@samsung.com>
Date:   Mon, 09 Jan 2017 08:37:25 +0100
From:   Andrzej Hajda <a.hajda@...sung.com>
To:     Inki Dae <inki.dae@...sung.com>,
        Andi Shyti <andi.shyti@...sung.com>
Cc:     Hoegeun Kwon <hoegeun.kwon@...sung.com>, robh@...nel.org,
        thierry.reding@...il.com, airlied@...ux.ie, kgene@...nel.org,
        krzk@...nel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org, cw00.choi@...sung.com,
        jh80.chung@...sung.com, Donghwa Lee <dh09.lee@...sung.com>,
        Hyungwon Hwang <human.hwang@...sung.com>
Subject: Re: [PATCH v7 3/4] drm/panel: Add support for S6E3HA2 panel driver on
 TM2 board

On 06.01.2017 09:36, Inki Dae wrote:
>
> 2017년 01월 06일 17:18에 Andi Shyti 이(가) 쓴 글:
>> Hi Inki,
>>
>> Thanks for the reply, but...
>>
>>>>> +static const struct drm_display_mode default_mode = {
>>>>> +	.clock = 222372,
>>>>> +	.hdisplay = 1440,
>>>>> +	.hsync_start = 1440 + 1,
>>>>> +	.hsync_end = 1440 + 1 + 1,
>>>>> +	.htotal = 1440 + 1 + 1 + 1,
>>>>> +	.vdisplay = 2560,
>>>>> +	.vsync_start = 2560 + 1,
>>>>> +	.vsync_end = 2560 + 1 + 1,
>>>>> +	.vtotal = 2560 + 1 + 1 + 15,
>>>>> +	.vrefresh = 60,
>>>>> +	.flags = 0,
>>>>> +};
>>>> how is this working with tm2e? Are these values valid for both
>>>> the boards?
>>> We don't need to consider tm2e board with two reasones,
>>> 1. there is no tm2e board support in mainline
>>> 2. the panel on tm2 would be a little bit different from one on tm2e
>> ... this display in the Tizen Kernel is supported by both:
>> tm2 [1] and tm2e [2]. The only differences are:
> Why tm2e dts file is in mainline? Seems communication miss with Chanwoo. :( 
>
>> TM2:
>>    clock-frequency = <14874444>;
>>    hactive = <1440>;
>>
>> TM2E:
>>    clock-frequency = <16523724>;
>>    hactive = <1600>;
>>
>> I don't know much about the differences you mention in point 2,
>> but it's a pity to drop support only because we don't want to put
>> in the dts the 'hactive', and 'clock-frequency' properties.
> Anyway, tm2e board is already in mainline so Panel driver may need to identify what kinds of panel is probed to decide porch values. I think there are relevant registers in MCU of the Panel device to check version or similar thing.

I think we can safely use different compatible string for tm2e - it uses
different display IC controller - s6e3hf2, driver will provide timings
based on it.
As far as I examined available specs/docs there is no reliable register
which can be used to safely distinguish it on runtime, but the docs I
have are far from completeness.

Regards
Andrzej

>
> Thanks.
>
>> Andi
>>
>> [1] https://git.tizen.org/cgit/platform/kernel/linux-exynos/tree/arch/arm64/boot/dts/exynos/exynos5433-tm2.dts?h=tizen#n1284
>> [2] https://git.tizen.org/cgit/platform/kernel/linux-exynos/tree/arch/arm64/boot/dts/exynos/exynos5433-tm2e.dts?h=tizen#n1270
>> --
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>> .
>>
>