Re: [PATCH] [MIPS] Add fix for loongson3 llsc errata

[James Cowgill <james dot cowgill at mips dot com>]

Hi,

On 24/01/18 01:57, Jiaxun Yang wrote:
> This patch adds fix for Loongson-3 llsc errata.
> 
> /gas
> 	* config/tc-mips.c (mips_fix_loongson3_llsc): New variables.
> 	(md_loongopts): Add New options -mfix-loongson3-llsc,
> 	-mno-fix-loongson3-llsc.
> 	(md_parse_option): Initialize variables via above options.
> 	(options): New enums for the above options.
> 	(md_assemble): Insert sync before ll/lld if fix enabled.
> 	* doc/c-mips.texi Document the -mfix-loongson3-llsc.
> 	* testsuit/gas/mips/loongson3a-4.d New.
> 	* testsuit/gas/mips/loongson3a-4.s New.

I'm interested to know what this errata is. Why do you need the extra
sync and what does it do?

Some time ago, I also noticed a kernel patch was submitted to do
something similar in their atomic routines. The patch also adds a sync
after some sc instructions as well. Is that not necessary?

https://patchwork.linux-mips.org/patch/16987/

Thanks,
James

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