Re: [PATCH 0/5] MIPS: xburst: add initial JZ4770 SoC support

[Sascha Hauer <s.hauer@pengutronix.de>]

Hi Antony,

On Sat, Apr 11, 2015 at 02:22:56AM +0300, Antony Pavlov wrote:
> This patchseries adds initial JZ4770 SoC and Ainol Novo7 Paladin tablet support.
> 
> The patchseries can be found on github:
>     https://github.com/frantony/barebox/tree/20150411.jz4770
> 
> The most notable problems and todos:
> 
>   * no PBL support; I have a PBL-enabled barebox version
>     for the tablet, so barebox can be used as only bootloader for tablet.
>     But this version is based on some dirty hacks
>     e.g. it uses special pre-compiled X-Boot blob for bootstraping.
> 
>     Nowadays barebox mips PBL is written in assembler
>     and I see no way to switch it to C. gcc-4.9.1 for mips has no __naked
>     directive support, see this gcc output
> 
>         $ cat > 1.c <<EOF;
>         int __attribute__((naked)) __attribute__((no_instrument_function)) main()
>         {
>         }
>         EOF
> 
>         $ /opt/mips-2014.11/bin/mips-linux-gnu-gcc -o 1.o 1.c
>         1.c:2:1: warning: 'naked' attribute directive ignored [-Wattributes]
>          {
>          ^
> 
>     So for moving X-Boot bootstrap C-code into barebox PBL we have to convert it
>     from C to assembler language :(

Is this really necessary? Only the entry point up to the point where you
setup the stack needs to be assembly, from then on C can be used.


> 
>     Please see JZ4770 bootstrap code in these repos:
> 
>         https://github.com/gcwnow/UBIBoot/
>         https://github.com/IngenicSemiconductor/X-BOOT_NPM801
> 
>   * no clk support just now; we can easely steal it from linux
>     JZ4780 support code (see wip-ci20-v4.1 branch in https://github.com/paulburton/linux);
> 
>   * no hardware clocksource support; this can be easely fixed,
>     see linux JZ4780 support code again;
>     also see https://github.com/frantony/barebox/blob/next.xburst.jz4770.20130511/arch/mips/mach-xburst/csrc-jz4770.c

Before merging this series I'd like to have clocksource support. Using
the dummy clocksource is fine during initial bringup, but I think merged
code should not depend on it.

Sascha

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