RE: 答复: [PATCH] MIPS: start.S: remove duplicate ADR macro definition

["Kevin Du Huanpeng" <u74147@gmail.com>]

Hi!
I am using this model:
WR720N   http://wiki.openwrt.org/toh/tp-link/tl-wr720n
note that, there is a very different model with the same name.
(*NOT* this one) http://www.tp-link.com/en/products/details/?model=TL-WR720N
but I suggest you to buy this model: wr703n
http://wiki.openwrt.org/ru/toh/tp-link/tl-wr703n
http://wiki.openwrt.org/toh/tp-link/tl-wr703n
it's even smaller. But only have one RJ45 port. The wr720n has two.
wr703n is cute.

I don't know if these two model available outside of china.
But there are some model very similar to these two.
and ar9331 based tp-link router:
https://github.com/pepe2k/u-boot_mod#supported-devices
http://wiki.openwrt.org/toh/tp-link/tl-mr10u

in china, we can buy it from
WR703N 99CNY http://item.yixun.com/item-216308.html?YTAG=3.21012001
WR720N 125CNY http://item.yixun.com/item-350056.html?YTAG=3.21012000
Or taobao.com, a site like Yahoo or ebay, C2C.

125CNY=21USD,99CNY=17USD,
but I don’t know why it is 64.99USD in amazon USA.
http://www.amazon.com/TP-Link-TL-WR720N-150Mbps-Wireless-N-Portable/dp/B00EYD1VKC/ref=sr_1_3?ie=UTF8&qid=1386231687&sr=8-3&keywords=wr720N

if you can't find it in your location, I can buy you one.
- - -
The AR9331 datasheet is available there:
http://see.sl088.com/w/images/6/69/AR9331.pdf

serial console access, hardware and many things are there:
http://wiki.openwrt.org/toh/tp-link/tl-wr703n

u-boot is here:
https://github.com/zhang3/u-boot_mod
forked from
https://github.com/pepe2k/u-boot_mod
thanks to pepe2k(https://github.com/pepe2k)

I have create a repository on github, now it's empty.
https://github.com/zhang3/barebox-wr720n
I will upload my source code and write document later.


...
DuHuanpeng

-----Original Message-----
From: Antony Pavlov [mailto:antonynpavlov@gmail.com] 
Sent: 2013年12月5日 12:35
To: Kevin Du Huanpeng
Subject: Re: 答复: [PATCH] MIPS: start.S: remove duplicate ADR macro definition

On Thu, 5 Dec 2013 01:25:04 +0800
"Kevin Du Huanpeng" <u74147@gmail.com> wrote:

> I am trying to port barebox on my TP-LINK WR720N router
> (SoC: AR9331 24KC, DRAM: 32MiB,  FLASH: 4MiB)

http://market.yandex.ru/model.xml?modelid=8444230

If it's your model then I can easely buy it in Moscow :)

> In the start.S, this ADR macro make me confuse...
> But finally, I find it 
> 	.macro  ADR rd label temp
> just used to get the label's VMA. (correct me if I am wrong) .
> in the start.S, it wants to get the _start 's VMA.
> Assuming the _start is the first instruction of barebox.
> Why not save the _start's VMA to ra when running the first instruction?
> By 
> 	bal __start
> 	nop
> 	...
> 	__start:
> I think the different between above and ADR is:
> My code overwrite the ra register.
> If any other bootloader or something call's barebox, It can't return.
> >Personally I have no objections on removing ADR macro.
> Just remove it from start.S
> 
> By the way, I really need help...
> Do you interested in porting barebox to ar9331?
> The router is quite cute and small, and very cheap!
> Just 125CNY, (20USD).
> You can find quit a lot information about it on OpenWRT.
> And there is a working u-boot for this router.
> https://github.com/pepe2k/u-boot_mod
> I have modify this u-boot and make it run In the kernel's position.
> https://github.com/zhang3/u-boot_mod
> So that the original u-boot can boot my u-boot.
> By done this,
> I modify the link address of barebox the same as the u-boot(second 
> one).
> 
>   
> 
> -----邮件原件-----
> 发件人: Antony Pavlov [mailto:antonynpavlov@gmail.com]
> 发送时间: 2013年12月5日 0:34
> 收件人: Kevin Du Huanpeng
> 主题: Re: [PATCH] MIPS: start.S: remove duplicate ADR macro definition
> 
> On Wed, 4 Dec 2013 20:47:47 +0800
> Kevin Du Huanpeng <u74147@gmail.com> wrote:
> 
> > hi, mips has a b/bal, why does mips have to use the macro: ADR in 
> > the start.S
> > 
> 
> Personally I have no objections on removing ADR macro. It has some disadvantages (e.g. it can't be used twice in one program because it uses global label).
> 
> If you want understand the situation with ADR macro you shoul track the MIPS barebox history.
> 
> My original MIPS barebox has no ADR macro. See head.S file and 
> especialy 'compute_offset' label in this patch 
> http://lists.infradead.org/pipermail/barebox/2011-June/003695.html
> 
> But after my publication Shinya Kuribayashi has appeared:
> http://lists.infradead.org/pipermail/barebox/2011-June/003707.html
> 
> Kuribayashi-san has his own (but not working) mips barebox implementation and Jean-Christophe enforced me to use Kuribayashi's start.S realisation (with ADR macro):
> http://lists.infradead.org/pipermail/barebox/2011-June/003715.html
> 
> As a result now we have start.S with ADR macro.
> 
> You want drop ADR macro from start.S, but IMHO we can drop relocation code from start.S completely!
> Today we have smart PBL (pre-boot loader) in barebox. This PBL can comress and relocate main barebox image. So we can easely drop relocation code from start.S:
> if you need relocation then just simply use PBL!
> 
> Can you please describe your interest in barebox for MIPS?
> That type of board do you use?
> 
> If you need any help on barebox for MIPS you are welcome!
> 
> > _start: bal __start
> > nop
> > __start:
> > addiu a0, ra, -8
> > a0, now is the _start's vma.
> > 
> > 
> > 2013/12/4 Antony Pavlov <antonynpavlov@gmail.com>:
> > > Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
> > > ---
> > >  arch/mips/boot/start.S | 22 +---------------------
> > >  1 file changed, 1 insertion(+), 21 deletions(-)
> > >
> > > diff --git a/arch/mips/boot/start.S b/arch/mips/boot/start.S index
> > > 7e2ae5e..d180157 100644
> > > --- a/arch/mips/boot/start.S
> > > +++ b/arch/mips/boot/start.S
> > > @@ -2,7 +2,6 @@
> > >   * Startup Code for MIPS CPU
> > >   *
> > >   * Copyright (C) 2011 Antony Pavlov <antonynpavlov@gmail.com>
> > > - * Used code copyrighted (C) 2009 by Shinya Kuribayashi <skuribay@pobox.com>
> > >   *
> > >   * This file is part of barebox.
> > >   * See file CREDITS for list of people who contributed to this project.
> > > @@ -24,26 +23,7 @@
> > >  #include <asm-generic/memory_layout.h>  #include 
> > > <generated/compile.h>  #include <generated/utsrelease.h>
> > > -
> > > -       /*
> > > -        * ADR macro instruction (inspired by ARM)
> > > -        *
> > > -        * ARM architecture doesn't have PC-relative jump instruction
> > > -        * like MIPS' B/BAL insns.  When ARM makes PC-relative jumps,
> > > -        * it uses ADR insn.  ADR is used to get a destination address
> > > -        * of 'label' against current PC.  With this, ARM can safely
> > > -        * make PC-relative jumps.
> > > -        */
> > > -       .macro  ADR rd label temp
> > > -       .set    push
> > > -       .set    noreorder
> > > -       move    \temp, ra                       # preserve ra beforehand
> > > -       bal     _pc
> > > -        nop
> > > -_pc:   addiu   \rd, ra, \label - _pc           # label is assumed to be
> > > -       move    ra, \temp                       # within pc +/- 32KB
> > > -       .set    pop
> > > -       .endm
> > > +#include <asm/pbl_macros.h>
> > >
> > >         .set noreorder
> > >         .text
> > > --
> > > 1.8.4.4
> > >
> 
> 
> --
> --
> Best regards,
>   Antony Pavlov
> 


--
--
Best regards,
  Antony Pavlov


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