Message-ID: <1520262650.8089.233.camel@mtkswgap22>
Date:   Mon, 5 Mar 2018 23:10:50 +0800
From:   Sean Wang <sean.wang@...iatek.com>
To:     Rob Herring <robh@...nel.org>
CC:     Mark Rutland <mark.rutland@....com>, <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v1 18/19] arm: dts: mt7623: add MT7623A reference boards

On Mon, 2018-03-05 at 08:10 -0600, Rob Herring wrote:
> On Fri, Mar 2, 2018 at 8:15 PM, Sean Wang <sean.wang@...iatek.com> wrote:
> > On Fri, 2018-03-02 at 09:45 -0600, Rob Herring wrote:
> >> On Fri, Feb 23, 2018 at 06:16:38PM +0800, sean.wang@...iatek.com wrote:
> >> > From: Sean Wang <sean.wang@...iatek.com>
> >> >
> >> > Add mt7623a-rfb.dtsi where most nodes can be inherited from
> >> > mt7623n-rfb.dtsi and keep these distinctions from MT7623A boards in
> >> > mt7623a-rfb.dtsi for most definition can be reused among MT7623A board
> >> > variants.
> >> >
> >> > MT7623A has its specific definition of power domain and thus we need
> >> > to change related devices such as audio, ethernet, crypto, high-speed
> >> > DMA, NAND, and USB controller to the power domain they specifically
> >> > belong to. In addition, MT7530 exists as built-in module inside MT7623A
> >> > SoC and I2C2 and UART[0-1] get being removed and UART2 have distinct pin
> >> > usage. Those all differences can be totally seen in mt7623a-rfb.dtsi.
> >> >
> >> > Signed-off-by: Sean Wang <sean.wang@...iatek.com>
> >> > ---
> >> >  arch/arm/boot/dts/Makefile             |  2 +
> >> >  arch/arm/boot/dts/mt7623a-rfb-emmc.dts | 22 +++++++++
> >> >  arch/arm/boot/dts/mt7623a-rfb-nand.dts | 26 +++++++++++
> >> >  arch/arm/boot/dts/mt7623a-rfb.dtsi     | 84 ++++++++++++++++++++++++++++++++++
> >> >  arch/arm/boot/dts/mt7623n-rfb.dtsi     | 15 ++++++
> >> >  5 files changed, 149 insertions(+)
> >> >  create mode 100644 arch/arm/boot/dts/mt7623a-rfb-emmc.dts
> >> >  create mode 100644 arch/arm/boot/dts/mt7623a-rfb-nand.dts
> >> >  create mode 100644 arch/arm/boot/dts/mt7623a-rfb.dtsi
> >> >
> >> > diff --git a/arch/arm/boot/dts/Makefile b/arch/arm/boot/dts/Makefile
> >> > index 5af6fce..818817c 100644
> >> > --- a/arch/arm/boot/dts/Makefile
> >> > +++ b/arch/arm/boot/dts/Makefile
> >> > @@ -1122,6 +1122,8 @@ dtb-$(CONFIG_ARCH_MEDIATEK) += \
> >> >     mt6580-evbp1.dtb \
> >> >     mt6589-aquaris5.dtb \
> >> >     mt6592-evb.dtb \
> >> > +   mt7623a-rfb-emmc.dtb \
> >> > +   mt7623a-rfb-nand.dtb \
> >> >     mt7623n-rfb-emmc.dtb \
> >> >     mt7623n-rfb-nand.dtb \
> >> >     mt7623n-bananapi-bpi-r2.dtb \
> >> > diff --git a/arch/arm/boot/dts/mt7623a-rfb-emmc.dts b/arch/arm/boot/dts/mt7623a-rfb-emmc.dts
> >> > new file mode 100644
> >> > index 0000000..ef6398e
> >> > --- /dev/null
> >> > +++ b/arch/arm/boot/dts/mt7623a-rfb-emmc.dts
> >> > @@ -0,0 +1,22 @@
> >> > +// SPDX-License-Identifier: GPL-2.0
> >> > +/*
> >> > + * Copyright (c) 2017-2018 MediaTek Inc.
> >> > + * Author: Sean Wang <sean.wang@...iatek.com>
> >> > + *
> >> > + */
> >> > +
> >> > +/dts-v1/;
> >> > +#include "mt7623a-rfb.dtsi"
> >> > +
> >> > +/ {
> >> > +   model = "MediaTek MT7623A with eMMC reference board";
> >> > +   compatible = "mediatek,mt7623a-rfb-emmc", "mediatek,mt7623";
> >> > +
> >> > +   chosen {
> >> > +           bootargs = "console=ttyS0,115200n8 earlyprintk";
> >>
> >> Use stdout-path instead. earlyprintk option only works for a kernel
> >> built with a debug uart at a fixed address, so drop it.
> >>
> >
> > thanks, I will try and have stdout-path instead.
> >
> > But for earlyprintk, our kernel can support and be built with a debug
> > uart at a fixed address and it is greatly useful to know what's going
> > on when a system hang happens on certain device's initialization prior
> > to uart initialization such as PCI device.
> 
> These days, you only need earlyprintk for *really* early console like
> in the assembly boot entry code and before the DT is unflattened. For
> anything else, use earlycon instead because earlycon is a runtime
> option.
> 
> > Thus, I consider to keep it there in special on such kinds of
> > development boards for debugging purpose.
> 
> Then add this option when you are doing debug. But for what's
> "shipped" in mainline, you should not have this enabled.
> 
> Rob

Okay, for these reasons, I will remove earlyprintk usage here
and try to use earlycon instead in the future.

Really thanks for your detailed explanation!

	Sean
> 
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