linux-kernel - Re: [PATCH v3] MIPS: pm-cps: Block system suspend when a JTAG probe is present

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Date:   Fri, 9 Mar 2018 13:55:49 +0000
From:   James Hogan <jhogan@...nel.org>
To:     Matt Redfearn <matt.redfearn@...s.com>
Cc:     Ralf Baechle <ralf@...ux-mips.org>, linux-mips@...ux-mips.org,
        Paul Burton <paul.burton@...s.com>,
        Dengcheng Zhu <dengcheng.zhu@...s.com>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v3] MIPS: pm-cps: Block system suspend when a JTAG probe
 is present

On Tue, Feb 20, 2018 at 09:58:16AM +0000, Matt Redfearn wrote:
> If a JTAG probe is connected to a MIPS cluster, then the CPC detects it
> and latches the CPC.STAT_CONF.EJTAG_PROBE bit to 1. While set,
> attempting to send a power-down command to a core will be blocked, and
> the CPC will instead send the core to clock-off state. This can
> interfere with systems fully entering a low power state where all
> cores, CM, GIC, etc are powered down.
> 
> Detect that a JTAG probe is / has been connected to the cluster and
> block the suspend attempt.
> 
> Attempting to suspend the system while a JTAG probe is connected now
> yields:
>  # echo mem > /sys/power/state
>  [   11.654000] PM: Syncing filesystems ... done.
>  [   11.658000] JTAG probe is connected - abort suspend
>  -sh: echo: write error: Operation not permitted
>  #
> 
> To restore suspend, the JTAG probe should be disconnected or put into
> quiescent state. Platform code can then clear the
> CPC.STAT_CONF.EJTAG_PROBE bit.
> 
> Reported-by: Ed Blake <ed.blake@...drel.com>
> Signed-off-by: Matt Redfearn <matt.redfearn@...s.com>

Thanks, applied for 4.17.

Cheers
James

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