linux-kernel - RE: [PATCH 3/4] ARCv2: smp: MCIP: remove debug aid to halt all cores when one halts

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Date:   Tue, 17 Jan 2017 20:13:14 +0000
From:   Alexey Brodkin <Alexey.Brodkin@...opsys.com>
To:     Vineet Gupta <Vineet.Gupta1@...opsys.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>
Subject: RE: [PATCH 3/4] ARCv2: smp: MCIP: remove debug aid to halt all
 cores when one halts

Hi Vineet,

> -----Original Message-----
> From: Vineet Gupta
> Sent: Monday, January 16, 2017 11:58 PM
> To: linux-snps-arc@...ts.infradead.org; Alexey Brodkin
> <abrodkin@...opsys.com>
> Cc: linux-kernel@...r.kernel.org; Vineet Gupta <vgupta@...opsys.com>
> Subject: [PATCH 3/4] ARCv2: smp: MCIP: remove debug aid to halt all cores
> when one halts
> 
> This was really usefull when doing initial bringup and also for occassional
> debug of software and hardware bugs. However in the new smp-boot
> regime, non masters will "self" halt even for run-on-reset configs. This will
> misinteract with the debug feature as in even master will get halted when
> the non masters self halt.
> 
> Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
> ---
>  arch/arc/kernel/mcip.c | 5 -----
>  1 file changed, 5 deletions(-)
> 
> diff --git a/arch/arc/kernel/mcip.c b/arch/arc/kernel/mcip.c index
> f39142acc89e..933382e0edd0 100644
> --- a/arch/arc/kernel/mcip.c
> +++ b/arch/arc/kernel/mcip.c
> @@ -101,11 +101,6 @@ static void mcip_probe_n_setup(void)
>  		IS_AVAIL1(mp.gfrc, "GFRC"));
> 
>  	cpuinfo_arc700[0].extn.gfrc = mp.gfrc;
> -
> -	if (mp.dbg) {
> -		__mcip_cmd_data(CMD_DEBUG_SET_SELECT, 0, 0xf);
> -		__mcip_cmd_data(CMD_DEBUG_SET_MASK, 0xf, 0xf);
> -	}
>  }

I've been doing that for quite some time locally because that used to be a must
for execution of SMP vmlinux in "pseudo"-UP mode, i.e. on SMP hardware but
with only 1 core being used.

I'm really happy to see this commit upstream - will definitely make life a bit simpler.

-Alexey