linux-kernel - Re: [PATCH v2 2/2] arm64: dts: Add Mediatek X20 Development Board support

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Date:   Wed, 18 Jul 2018 17:07:38 +0200
From:   Matthias Brugger <matthias.bgg@...il.com>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     robh+dt@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, taiten.peng@...aro.org,
        daniel.thompson@...aro.org, amit.kucheria@...aro.org,
        manivannanece23@...il.com
Subject: Re: [PATCH v2 2/2] arm64: dts: Add Mediatek X20 Development Board
 support



On 17/07/18 16:04, Manivannan Sadhasivam wrote:
> Hi Matthias,
> 
> On Mon, Jul 16, 2018 at 03:24:44PM +0200, Matthias Brugger wrote:
>> Hi Manivanna,
>>
>> On 05/06/18 18:34, Manivannan Sadhasivam wrote:
>>> Add initial device tree support for Mediatek X20 Development Board
>>> based on MT6797 Deca core SoC. This board is one of the 96Boards
>>> Consumer Edition platform.
>>>
>>> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
>>> ---
>>>  arch/arm64/boot/dts/mediatek/Makefile         |  1 +
>>>  .../boot/dts/mediatek/mt6797-x20-dev.dts      | 33 +++++++++++++++++++
>>>  2 files changed, 34 insertions(+)
>>>  create mode 100644 arch/arm64/boot/dts/mediatek/mt6797-x20-dev.dts
>>>
>>> diff --git a/arch/arm64/boot/dts/mediatek/Makefile b/arch/arm64/boot/dts/mediatek/Makefile
>>> index ac17f60f998c..5b7fd6ad96e4 100644
>>> --- a/arch/arm64/boot/dts/mediatek/Makefile
>>> +++ b/arch/arm64/boot/dts/mediatek/Makefile
>>> @@ -3,5 +3,6 @@ dtb-$(CONFIG_ARCH_MEDIATEK) += mt2712-evb.dtb
>>>  dtb-$(CONFIG_ARCH_MEDIATEK) += mt6755-evb.dtb
>>>  dtb-$(CONFIG_ARCH_MEDIATEK) += mt6795-evb.dtb
>>>  dtb-$(CONFIG_ARCH_MEDIATEK) += mt6797-evb.dtb
>>> +dtb-$(CONFIG_ARCH_MEDIATEK) += mt6797-x20-dev.dtb
>>>  dtb-$(CONFIG_ARCH_MEDIATEK) += mt7622-rfb1.dtb
>>>  dtb-$(CONFIG_ARCH_MEDIATEK) += mt8173-evb.dtb
>>> diff --git a/arch/arm64/boot/dts/mediatek/mt6797-x20-dev.dts b/arch/arm64/boot/dts/mediatek/mt6797-x20-dev.dts
>>> new file mode 100644
>>> index 000000000000..2c09ca95d9e2
>>> --- /dev/null
>>> +++ b/arch/arm64/boot/dts/mediatek/mt6797-x20-dev.dts
>>> @@ -0,0 +1,33 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +/*
>>> + * Device Tree Source for MediaTek X20 Development Board
>>> + *
>>> + * Copyright (C) 2018, Linaro Ltd.
>>> + *
>>> + */
>>> +
>>> +/dts-v1/;
>>> +
>>> +#include "mt6797.dtsi"
>>> +
>>> +/ {
>>> +	model = "Mediatek X20 Development Board";
>>> +	compatible = "archermind,mt6797-x20-dev", "mediatek,mt6797";
>>> +
>>> +	aliases {
>>> +		serial0 = &uart1;
>>> +	};
>>
>> Sorry for the late answer.
>> Why did you use uart1 instead of uart0?
>> I know that uart0 is used by the bootloader, but because of their exotic flash
>> procedure I find it quite useful to see this messages in my serial connection.
>> Of course you can only use 921600 baudrate then.
>>
> 
> The reason is, most of the Mezzanine boards use USB to UART bridge on the
> UART1 port available on the Low Speed Expansion header. Additionally, the
> convention followed by most of the Consumer Edition 96Boards is to use UART1
> as the debug serial port. That's why eventhough the bootloader is using UART0,
> I forced the kernel to use UART1.
> 

Sounds reasonable, I don't have this 96 boards adapter and I forgot about it.

>>> +
>>> +	memory@...00000 {
>>> +		device_type = "memory";
>>> +		reg = <0 0x40000000 0 0x1e605000>;
>>
>> How comes this strange number for the memory size?
>>
> 
> Actually, the memory size is extracted from the downstream kernel [1].
> 

Hm, Archermind "Helio X20 Development Board Hardware Manual" talks about 2GB
LPDDR3-SDRAM. Would you mind to check if that is actually true?

>> BTW do you know the differences between the EVB board and the x20 one?
>> I used the evb dts for booting up to now.
>>
> 
> Sorry, I don't know the difference between both boards!

Sure, no problem :)

Regards,
Matthias

> 
> Thanks,
> Mani
> 
> [1] https://github.com/helio-x20/linux/blob/helio-x20/arch/arm64/boot/dts/amt6797_64_open.dts#L8
> 
>> Best regards,
>> Matthias
>>
>>> +	};
>>> +
>>> +	chosen {
>>> +		stdout-path = "serial0:115200n8";
>>> +	};
>>> +};
>>> +
>>> +&uart1 {
>>> +	status = "okay";
>>> +};
>>>