Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Unverified Commit b2ed33a8 authored by Matt Redfearn's avatar Matt Redfearn Committed by James Hogan
Browse files

MIPS: pm-cps: Block system suspend when a JTAG probe is present 



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: default avatarEd Blake <ed.blake@sondrel.com>
Signed-off-by: default avatarMatt Redfearn <matt.redfearn@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/18641/


Signed-off-by: default avatarJames Hogan <jhogan@kernel.org>
parent ce6828fa

arch/mips/kernel/pm-cps.c

+31 −0
Original line number Diff line number Diff line
@@ -12,6 +12,7 @@ 
#include <linux/init.h>

#include <linux/percpu.h>

#include <linux/slab.h>

#include <linux/suspend.h>



#include <asm/asm-offsets.h>

#include <asm/cacheflush.h>
@@ -670,6 +671,34 @@ static int cps_pm_online_cpu(unsigned int cpu) 
	return 0;

}



static int cps_pm_power_notifier(struct notifier_block *this,

				 unsigned long event, void *ptr)

{

	unsigned int stat;



	switch (event) {

	case PM_SUSPEND_PREPARE:

		stat = read_cpc_cl_stat_conf();

		/*

		 * If we're attempting to suspend the system and power down all

		 * of the cores, the JTAG detect bit indicates that the CPC will

		 * instead put the cores into clock-off state. In this state

		 * a connected debugger can cause the CPU to attempt

		 * interactions with the powered down system. At best this will

		 * fail. At worst, it can hang the NoC, requiring a hard reset.

		 * To avoid this, just block system suspend if a JTAG probe

		 * is detected.

		 */

		if (stat & CPC_Cx_STAT_CONF_EJTAG_PROBE) {

			pr_warn("JTAG probe is connected - abort suspend\n");

			return NOTIFY_BAD;

		}

		return NOTIFY_DONE;

	default:

		return NOTIFY_DONE;

	}

}



static int __init cps_pm_init(void)

{

	/* A CM is required for all non-coherent states */
@@ -705,6 +734,8 @@ static int __init cps_pm_init(void) 
		pr_warn("pm-cps: no CPC, clock & power gating unavailable\n");

	}



	pm_notifier(cps_pm_power_notifier, 0);



	return cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mips/cps_pm:online",

				 cps_pm_online_cpu, NULL);

}