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

[Manivannan Sadhasivam]

Hi Matthias,

On Wed, Jul 18, 2018 at 05:07:38PM +0200, Matthias Brugger wrote:
> 
> 
> 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@xxxxxxxxxx>
> >>> ---
> >>>  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.
> 

That's fine :)

> >>> +
> >>> +	memory@40000000 {
> >>> +		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?
> 

Yes, it is 2GB. Shall I change the size to 0x80000000?

Thanks,
Mani

> >> 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";
> >>> +};
> >>>