MIPS: pm-cps: Block system suspend when a JTAG probe is present (b2ed33a8) · Commits · 戴 / test

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@sondrel.com> Signed-off-by:

Matt 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:

James Hogan <jhogan@kernel.org>

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);
		}

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