Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 742 insertions, 0 deletions

diff --git a/arch/mips/kernel/pm-cps.c b/arch/mips/kernel/pm-cps.c
new file mode 100644
index 000000000..55c3fbeb2
--- /dev/null
+++ b/arch/mips/kernel/pm-cps.c
@@ -0,0 +1,742 @@
+/*
+ * Copyright (C) 2014 Imagination Technologies
+ * Author: Paul Burton <paul.burton@mips.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation;  either version 2 of the  License, or (at your
+ * option) any later version.
+ */
+
+#include <linux/cpuhotplug.h>
+#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>
+#include <asm/cacheops.h>
+#include <asm/idle.h>
+#include <asm/mips-cps.h>
+#include <asm/mipsmtregs.h>
+#include <asm/pm.h>
+#include <asm/pm-cps.h>
+#include <asm/smp-cps.h>
+#include <asm/uasm.h>
+
+/*
+ * cps_nc_entry_fn - type of a generated non-coherent state entry function
+ * @online: the count of online coupled VPEs
+ * @nc_ready_count: pointer to a non-coherent mapping of the core ready_count
+ *
+ * The code entering & exiting non-coherent states is generated at runtime
+ * using uasm, in order to ensure that the compiler cannot insert a stray
+ * memory access at an unfortunate time and to allow the generation of optimal
+ * core-specific code particularly for cache routines. If coupled_coherence
+ * is non-zero and this is the entry function for the CPS_PM_NC_WAIT state,
+ * returns the number of VPEs that were in the wait state at the point this
+ * VPE left it. Returns garbage if coupled_coherence is zero or this is not
+ * the entry function for CPS_PM_NC_WAIT.
+ */
+typedef unsigned (*cps_nc_entry_fn)(unsigned online, u32 *nc_ready_count);
+
+/*
+ * The entry point of the generated non-coherent idle state entry/exit
+ * functions. Actually per-core rather than per-CPU.
+ */
+static DEFINE_PER_CPU_READ_MOSTLY(cps_nc_entry_fn[CPS_PM_STATE_COUNT],
+				  nc_asm_enter);
+
+/* Bitmap indicating which states are supported by the system */
+static DECLARE_BITMAP(state_support, CPS_PM_STATE_COUNT);
+
+/*
+ * Indicates the number of coupled VPEs ready to operate in a non-coherent
+ * state. Actually per-core rather than per-CPU.
+ */
+static DEFINE_PER_CPU_ALIGNED(u32*, ready_count);
+
+/* Indicates online CPUs coupled with the current CPU */
+static DEFINE_PER_CPU_ALIGNED(cpumask_t, online_coupled);
+
+/*
+ * Used to synchronize entry to deep idle states. Actually per-core rather
+ * than per-CPU.
+ */
+static DEFINE_PER_CPU_ALIGNED(atomic_t, pm_barrier);
+
+/* Saved CPU state across the CPS_PM_POWER_GATED state */
+DEFINE_PER_CPU_ALIGNED(struct mips_static_suspend_state, cps_cpu_state);
+
+/* A somewhat arbitrary number of labels & relocs for uasm */
+static struct uasm_label labels[32];
+static struct uasm_reloc relocs[32];
+
+enum mips_reg {
+	zero, at, v0, v1, a0, a1, a2, a3,
+	t0, t1, t2, t3, t4, t5, t6, t7,
+	s0, s1, s2, s3, s4, s5, s6, s7,
+	t8, t9, k0, k1, gp, sp, fp, ra,
+};
+
+bool cps_pm_support_state(enum cps_pm_state state)
+{
+	return test_bit(state, state_support);
+}
+
+static void coupled_barrier(atomic_t *a, unsigned online)
+{
+	/*
+	 * This function is effectively the same as
+	 * cpuidle_coupled_parallel_barrier, which can't be used here since
+	 * there's no cpuidle device.
+	 */
+
+	if (!coupled_coherence)
+		return;
+
+	smp_mb__before_atomic();
+	atomic_inc(a);
+
+	while (atomic_read(a) < online)
+		cpu_relax();
+
+	if (atomic_inc_return(a) == online * 2) {
+		atomic_set(a, 0);
+		return;
+	}
+
+	while (atomic_read(a) > online)
+		cpu_relax();
+}
+
+int cps_pm_enter_state(enum cps_pm_state state)
+{
+	unsigned cpu = smp_processor_id();
+	unsigned core = cpu_core(&current_cpu_data);
+	unsigned online, left;
+	cpumask_t *coupled_mask = this_cpu_ptr(&online_coupled);
+	u32 *core_ready_count, *nc_core_ready_count;
+	void *nc_addr;
+	cps_nc_entry_fn entry;
+	struct core_boot_config *core_cfg;
+	struct vpe_boot_config *vpe_cfg;
+
+	/* Check that there is an entry function for this state */
+	entry = per_cpu(nc_asm_enter, core)[state];
+	if (!entry)
+		return -EINVAL;
+
+	/* Calculate which coupled CPUs (VPEs) are online */
+#if defined(CONFIG_MIPS_MT) || defined(CONFIG_CPU_MIPSR6)
+	if (cpu_online(cpu)) {
+		cpumask_and(coupled_mask, cpu_online_mask,
+			    &cpu_sibling_map[cpu]);
+		online = cpumask_weight(coupled_mask);
+		cpumask_clear_cpu(cpu, coupled_mask);
+	} else
+#endif
+	{
+		cpumask_clear(coupled_mask);
+		online = 1;
+	}
+
+	/* Setup the VPE to run mips_cps_pm_restore when started again */
+	if (IS_ENABLED(CONFIG_CPU_PM) && state == CPS_PM_POWER_GATED) {
+		/* Power gating relies upon CPS SMP */
+		if (!mips_cps_smp_in_use())
+			return -EINVAL;
+
+		core_cfg = &mips_cps_core_bootcfg[core];
+		vpe_cfg = &core_cfg->vpe_config[cpu_vpe_id(&current_cpu_data)];
+		vpe_cfg->pc = (unsigned long)mips_cps_pm_restore;
+		vpe_cfg->gp = (unsigned long)current_thread_info();
+		vpe_cfg->sp = 0;
+	}
+
+	/* Indicate that this CPU might not be coherent */
+	cpumask_clear_cpu(cpu, &cpu_coherent_mask);
+	smp_mb__after_atomic();
+
+	/* Create a non-coherent mapping of the core ready_count */
+	core_ready_count = per_cpu(ready_count, core);
+	nc_addr = kmap_noncoherent(virt_to_page(core_ready_count),
+				   (unsigned long)core_ready_count);
+	nc_addr += ((unsigned long)core_ready_count & ~PAGE_MASK);
+	nc_core_ready_count = nc_addr;
+
+	/* Ensure ready_count is zero-initialised before the assembly runs */
+	WRITE_ONCE(*nc_core_ready_count, 0);
+	coupled_barrier(&per_cpu(pm_barrier, core), online);
+
+	/* Run the generated entry code */
+	left = entry(online, nc_core_ready_count);
+
+	/* Remove the non-coherent mapping of ready_count */
+	kunmap_noncoherent();
+
+	/* Indicate that this CPU is definitely coherent */
+	cpumask_set_cpu(cpu, &cpu_coherent_mask);
+
+	/*
+	 * If this VPE is the first to leave the non-coherent wait state then
+	 * it needs to wake up any coupled VPEs still running their wait
+	 * instruction so that they return to cpuidle, which can then complete
+	 * coordination between the coupled VPEs & provide the governor with
+	 * a chance to reflect on the length of time the VPEs were in the
+	 * idle state.
+	 */
+	if (coupled_coherence && (state == CPS_PM_NC_WAIT) && (left == online))
+		arch_send_call_function_ipi_mask(coupled_mask);
+
+	return 0;
+}
+
+static void cps_gen_cache_routine(u32 **pp, struct uasm_label **pl,
+				  struct uasm_reloc **pr,
+				  const struct cache_desc *cache,
+				  unsigned op, int lbl)
+{
+	unsigned cache_size = cache->ways << cache->waybit;
+	unsigned i;
+	const unsigned unroll_lines = 32;
+
+	/* If the cache isn't present this function has it easy */
+	if (cache->flags & MIPS_CACHE_NOT_PRESENT)
+		return;
+
+	/* Load base address */
+	UASM_i_LA(pp, t0, (long)CKSEG0);
+
+	/* Calculate end address */
+	if (cache_size < 0x8000)
+		uasm_i_addiu(pp, t1, t0, cache_size);
+	else
+		UASM_i_LA(pp, t1, (long)(CKSEG0 + cache_size));
+
+	/* Start of cache op loop */
+	uasm_build_label(pl, *pp, lbl);
+
+	/* Generate the cache ops */
+	for (i = 0; i < unroll_lines; i++) {
+		if (cpu_has_mips_r6) {
+			uasm_i_cache(pp, op, 0, t0);
+			uasm_i_addiu(pp, t0, t0, cache->linesz);
+		} else {
+			uasm_i_cache(pp, op, i * cache->linesz, t0);
+		}
+	}
+
+	if (!cpu_has_mips_r6)
+		/* Update the base address */
+		uasm_i_addiu(pp, t0, t0, unroll_lines * cache->linesz);
+
+	/* Loop if we haven't reached the end address yet */
+	uasm_il_bne(pp, pr, t0, t1, lbl);
+	uasm_i_nop(pp);
+}
+
+static int cps_gen_flush_fsb(u32 **pp, struct uasm_label **pl,
+			     struct uasm_reloc **pr,
+			     const struct cpuinfo_mips *cpu_info,
+			     int lbl)
+{
+	unsigned i, fsb_size = 8;
+	unsigned num_loads = (fsb_size * 3) / 2;
+	unsigned line_stride = 2;
+	unsigned line_size = cpu_info->dcache.linesz;
+	unsigned perf_counter, perf_event;
+	unsigned revision = cpu_info->processor_id & PRID_REV_MASK;
+
+	/*
+	 * Determine whether this CPU requires an FSB flush, and if so which
+	 * performance counter/event reflect stalls due to a full FSB.
+	 */
+	switch (__get_cpu_type(cpu_info->cputype)) {
+	case CPU_INTERAPTIV:
+		perf_counter = 1;
+		perf_event = 51;
+		break;
+
+	case CPU_PROAPTIV:
+		/* Newer proAptiv cores don't require this workaround */
+		if (revision >= PRID_REV_ENCODE_332(1, 1, 0))
+			return 0;
+
+		/* On older ones it's unavailable */
+		return -1;
+
+	default:
+		/* Assume that the CPU does not need this workaround */
+		return 0;
+	}
+
+	/*
+	 * Ensure that the fill/store buffer (FSB) is not holding the results
+	 * of a prefetch, since if it is then the CPC sequencer may become
+	 * stuck in the D3 (ClrBus) state whilst entering a low power state.
+	 */
+
+	/* Preserve perf counter setup */
+	uasm_i_mfc0(pp, t2, 25, (perf_counter * 2) + 0); /* PerfCtlN */
+	uasm_i_mfc0(pp, t3, 25, (perf_counter * 2) + 1); /* PerfCntN */
+
+	/* Setup perf counter to count FSB full pipeline stalls */
+	uasm_i_addiu(pp, t0, zero, (perf_event << 5) | 0xf);
+	uasm_i_mtc0(pp, t0, 25, (perf_counter * 2) + 0); /* PerfCtlN */
+	uasm_i_ehb(pp);
+	uasm_i_mtc0(pp, zero, 25, (perf_counter * 2) + 1); /* PerfCntN */
+	uasm_i_ehb(pp);
+
+	/* Base address for loads */
+	UASM_i_LA(pp, t0, (long)CKSEG0);
+
+	/* Start of clear loop */
+	uasm_build_label(pl, *pp, lbl);
+
+	/* Perform some loads to fill the FSB */
+	for (i = 0; i < num_loads; i++)
+		uasm_i_lw(pp, zero, i * line_size * line_stride, t0);
+
+	/*
+	 * Invalidate the new D-cache entries so that the cache will need
+	 * refilling (via the FSB) if the loop is executed again.
+	 */
+	for (i = 0; i < num_loads; i++) {
+		uasm_i_cache(pp, Hit_Invalidate_D,
+			     i * line_size * line_stride, t0);
+		uasm_i_cache(pp, Hit_Writeback_Inv_SD,
+			     i * line_size * line_stride, t0);
+	}
+
+	/* Barrier ensuring previous cache invalidates are complete */
+	uasm_i_sync(pp, STYPE_SYNC);
+	uasm_i_ehb(pp);
+
+	/* Check whether the pipeline stalled due to the FSB being full */
+	uasm_i_mfc0(pp, t1, 25, (perf_counter * 2) + 1); /* PerfCntN */
+
+	/* Loop if it didn't */
+	uasm_il_beqz(pp, pr, t1, lbl);
+	uasm_i_nop(pp);
+
+	/* Restore perf counter 1. The count may well now be wrong... */
+	uasm_i_mtc0(pp, t2, 25, (perf_counter * 2) + 0); /* PerfCtlN */
+	uasm_i_ehb(pp);
+	uasm_i_mtc0(pp, t3, 25, (perf_counter * 2) + 1); /* PerfCntN */
+	uasm_i_ehb(pp);
+
+	return 0;
+}
+
+static void cps_gen_set_top_bit(u32 **pp, struct uasm_label **pl,
+				struct uasm_reloc **pr,
+				unsigned r_addr, int lbl)
+{
+	uasm_i_lui(pp, t0, uasm_rel_hi(0x80000000));
+	uasm_build_label(pl, *pp, lbl);
+	uasm_i_ll(pp, t1, 0, r_addr);
+	uasm_i_or(pp, t1, t1, t0);
+	uasm_i_sc(pp, t1, 0, r_addr);
+	uasm_il_beqz(pp, pr, t1, lbl);
+	uasm_i_nop(pp);
+}
+
+static void *cps_gen_entry_code(unsigned cpu, enum cps_pm_state state)
+{
+	struct uasm_label *l = labels;
+	struct uasm_reloc *r = relocs;
+	u32 *buf, *p;
+	const unsigned r_online = a0;
+	const unsigned r_nc_count = a1;
+	const unsigned r_pcohctl = t7;
+	const unsigned max_instrs = 256;
+	unsigned cpc_cmd;
+	int err;
+	enum {
+		lbl_incready = 1,
+		lbl_poll_cont,
+		lbl_secondary_hang,
+		lbl_disable_coherence,
+		lbl_flush_fsb,
+		lbl_invicache,
+		lbl_flushdcache,
+		lbl_hang,
+		lbl_set_cont,
+		lbl_secondary_cont,
+		lbl_decready,
+	};
+
+	/* Allocate a buffer to hold the generated code */
+	p = buf = kcalloc(max_instrs, sizeof(u32), GFP_KERNEL);
+	if (!buf)
+		return NULL;
+
+	/* Clear labels & relocs ready for (re)use */
+	memset(labels, 0, sizeof(labels));
+	memset(relocs, 0, sizeof(relocs));
+
+	if (IS_ENABLED(CONFIG_CPU_PM) && state == CPS_PM_POWER_GATED) {
+		/* Power gating relies upon CPS SMP */
+		if (!mips_cps_smp_in_use())
+			goto out_err;
+
+		/*
+		 * Save CPU state. Note the non-standard calling convention
+		 * with the return address placed in v0 to avoid clobbering
+		 * the ra register before it is saved.
+		 */
+		UASM_i_LA(&p, t0, (long)mips_cps_pm_save);
+		uasm_i_jalr(&p, v0, t0);
+		uasm_i_nop(&p);
+	}
+
+	/*
+	 * Load addresses of required CM & CPC registers. This is done early
+	 * because they're needed in both the enable & disable coherence steps
+	 * but in the coupled case the enable step will only run on one VPE.
+	 */
+	UASM_i_LA(&p, r_pcohctl, (long)addr_gcr_cl_coherence());
+
+	if (coupled_coherence) {
+		/* Increment ready_count */
+		uasm_i_sync(&p, STYPE_SYNC_MB);
+		uasm_build_label(&l, p, lbl_incready);
+		uasm_i_ll(&p, t1, 0, r_nc_count);
+		uasm_i_addiu(&p, t2, t1, 1);
+		uasm_i_sc(&p, t2, 0, r_nc_count);
+		uasm_il_beqz(&p, &r, t2, lbl_incready);
+		uasm_i_addiu(&p, t1, t1, 1);
+
+		/* Barrier ensuring all CPUs see the updated r_nc_count value */
+		uasm_i_sync(&p, STYPE_SYNC_MB);
+
+		/*
+		 * If this is the last VPE to become ready for non-coherence
+		 * then it should branch below.
+		 */
+		uasm_il_beq(&p, &r, t1, r_online, lbl_disable_coherence);
+		uasm_i_nop(&p);
+
+		if (state < CPS_PM_POWER_GATED) {
+			/*
+			 * Otherwise this is not the last VPE to become ready
+			 * for non-coherence. It needs to wait until coherence
+			 * has been disabled before proceeding, which it will do
+			 * by polling for the top bit of ready_count being set.
+			 */
+			uasm_i_addiu(&p, t1, zero, -1);
+			uasm_build_label(&l, p, lbl_poll_cont);
+			uasm_i_lw(&p, t0, 0, r_nc_count);
+			uasm_il_bltz(&p, &r, t0, lbl_secondary_cont);
+			uasm_i_ehb(&p);
+			if (cpu_has_mipsmt)
+				uasm_i_yield(&p, zero, t1);
+			uasm_il_b(&p, &r, lbl_poll_cont);
+			uasm_i_nop(&p);
+		} else {
+			/*
+			 * The core will lose power & this VPE will not continue
+			 * so it can simply halt here.
+			 */
+			if (cpu_has_mipsmt) {
+				/* Halt the VPE via C0 tchalt register */
+				uasm_i_addiu(&p, t0, zero, TCHALT_H);
+				uasm_i_mtc0(&p, t0, 2, 4);
+			} else if (cpu_has_vp) {
+				/* Halt the VP via the CPC VP_STOP register */
+				unsigned int vpe_id;
+
+				vpe_id = cpu_vpe_id(&cpu_data[cpu]);
+				uasm_i_addiu(&p, t0, zero, 1 << vpe_id);
+				UASM_i_LA(&p, t1, (long)addr_cpc_cl_vp_stop());
+				uasm_i_sw(&p, t0, 0, t1);
+			} else {
+				BUG();
+			}
+			uasm_build_label(&l, p, lbl_secondary_hang);
+			uasm_il_b(&p, &r, lbl_secondary_hang);
+			uasm_i_nop(&p);
+		}
+	}
+
+	/*
+	 * This is the point of no return - this VPE will now proceed to
+	 * disable coherence. At this point we *must* be sure that no other
+	 * VPE within the core will interfere with the L1 dcache.
+	 */
+	uasm_build_label(&l, p, lbl_disable_coherence);
+
+	/* Invalidate the L1 icache */
+	cps_gen_cache_routine(&p, &l, &r, &cpu_data[cpu].icache,
+			      Index_Invalidate_I, lbl_invicache);
+
+	/* Writeback & invalidate the L1 dcache */
+	cps_gen_cache_routine(&p, &l, &r, &cpu_data[cpu].dcache,
+			      Index_Writeback_Inv_D, lbl_flushdcache);
+
+	/* Barrier ensuring previous cache invalidates are complete */
+	uasm_i_sync(&p, STYPE_SYNC);
+	uasm_i_ehb(&p);
+
+	if (mips_cm_revision() < CM_REV_CM3) {
+		/*
+		* Disable all but self interventions. The load from COHCTL is
+		* defined by the interAptiv & proAptiv SUMs as ensuring that the
+		*  operation resulting from the preceding store is complete.
+		*/
+		uasm_i_addiu(&p, t0, zero, 1 << cpu_core(&cpu_data[cpu]));
+		uasm_i_sw(&p, t0, 0, r_pcohctl);
+		uasm_i_lw(&p, t0, 0, r_pcohctl);
+
+		/* Barrier to ensure write to coherence control is complete */
+		uasm_i_sync(&p, STYPE_SYNC);
+		uasm_i_ehb(&p);
+	}
+
+	/* Disable coherence */
+	uasm_i_sw(&p, zero, 0, r_pcohctl);
+	uasm_i_lw(&p, t0, 0, r_pcohctl);
+
+	if (state >= CPS_PM_CLOCK_GATED) {
+		err = cps_gen_flush_fsb(&p, &l, &r, &cpu_data[cpu],
+					lbl_flush_fsb);
+		if (err)
+			goto out_err;
+
+		/* Determine the CPC command to issue */
+		switch (state) {
+		case CPS_PM_CLOCK_GATED:
+			cpc_cmd = CPC_Cx_CMD_CLOCKOFF;
+			break;
+		case CPS_PM_POWER_GATED:
+			cpc_cmd = CPC_Cx_CMD_PWRDOWN;
+			break;
+		default:
+			BUG();
+			goto out_err;
+		}
+
+		/* Issue the CPC command */
+		UASM_i_LA(&p, t0, (long)addr_cpc_cl_cmd());
+		uasm_i_addiu(&p, t1, zero, cpc_cmd);
+		uasm_i_sw(&p, t1, 0, t0);
+
+		if (state == CPS_PM_POWER_GATED) {
+			/* If anything goes wrong just hang */
+			uasm_build_label(&l, p, lbl_hang);
+			uasm_il_b(&p, &r, lbl_hang);
+			uasm_i_nop(&p);
+
+			/*
+			 * There's no point generating more code, the core is
+			 * powered down & if powered back up will run from the
+			 * reset vector not from here.
+			 */
+			goto gen_done;
+		}
+
+		/* Barrier to ensure write to CPC command is complete */
+		uasm_i_sync(&p, STYPE_SYNC);
+		uasm_i_ehb(&p);
+	}
+
+	if (state == CPS_PM_NC_WAIT) {
+		/*
+		 * At this point it is safe for all VPEs to proceed with
+		 * execution. This VPE will set the top bit of ready_count
+		 * to indicate to the other VPEs that they may continue.
+		 */
+		if (coupled_coherence)
+			cps_gen_set_top_bit(&p, &l, &r, r_nc_count,
+					    lbl_set_cont);
+
+		/*
+		 * VPEs which did not disable coherence will continue
+		 * executing, after coherence has been disabled, from this
+		 * point.
+		 */
+		uasm_build_label(&l, p, lbl_secondary_cont);
+
+		/* Now perform our wait */
+		uasm_i_wait(&p, 0);
+	}
+
+	/*
+	 * Re-enable coherence. Note that for CPS_PM_NC_WAIT all coupled VPEs
+	 * will run this. The first will actually re-enable coherence & the
+	 * rest will just be performing a rather unusual nop.
+	 */
+	uasm_i_addiu(&p, t0, zero, mips_cm_revision() < CM_REV_CM3
+				? CM_GCR_Cx_COHERENCE_COHDOMAINEN
+				: CM3_GCR_Cx_COHERENCE_COHEN);
+
+	uasm_i_sw(&p, t0, 0, r_pcohctl);
+	uasm_i_lw(&p, t0, 0, r_pcohctl);
+
+	/* Barrier to ensure write to coherence control is complete */
+	uasm_i_sync(&p, STYPE_SYNC);
+	uasm_i_ehb(&p);
+
+	if (coupled_coherence && (state == CPS_PM_NC_WAIT)) {
+		/* Decrement ready_count */
+		uasm_build_label(&l, p, lbl_decready);
+		uasm_i_sync(&p, STYPE_SYNC_MB);
+		uasm_i_ll(&p, t1, 0, r_nc_count);
+		uasm_i_addiu(&p, t2, t1, -1);
+		uasm_i_sc(&p, t2, 0, r_nc_count);
+		uasm_il_beqz(&p, &r, t2, lbl_decready);
+		uasm_i_andi(&p, v0, t1, (1 << fls(smp_num_siblings)) - 1);
+
+		/* Barrier ensuring all CPUs see the updated r_nc_count value */
+		uasm_i_sync(&p, STYPE_SYNC_MB);
+	}
+
+	if (coupled_coherence && (state == CPS_PM_CLOCK_GATED)) {
+		/*
+		 * At this point it is safe for all VPEs to proceed with
+		 * execution. This VPE will set the top bit of ready_count
+		 * to indicate to the other VPEs that they may continue.
+		 */
+		cps_gen_set_top_bit(&p, &l, &r, r_nc_count, lbl_set_cont);
+
+		/*
+		 * This core will be reliant upon another core sending a
+		 * power-up command to the CPC in order to resume operation.
+		 * Thus an arbitrary VPE can't trigger the core leaving the
+		 * idle state and the one that disables coherence might as well
+		 * be the one to re-enable it. The rest will continue from here
+		 * after that has been done.
+		 */
+		uasm_build_label(&l, p, lbl_secondary_cont);
+
+		/* Barrier ensuring all CPUs see the updated r_nc_count value */
+		uasm_i_sync(&p, STYPE_SYNC_MB);
+	}
+
+	/* The core is coherent, time to return to C code */
+	uasm_i_jr(&p, ra);
+	uasm_i_nop(&p);
+
+gen_done:
+	/* Ensure the code didn't exceed the resources allocated for it */
+	BUG_ON((p - buf) > max_instrs);
+	BUG_ON((l - labels) > ARRAY_SIZE(labels));
+	BUG_ON((r - relocs) > ARRAY_SIZE(relocs));
+
+	/* Patch branch offsets */
+	uasm_resolve_relocs(relocs, labels);
+
+	/* Flush the icache */
+	local_flush_icache_range((unsigned long)buf, (unsigned long)p);
+
+	return buf;
+out_err:
+	kfree(buf);
+	return NULL;
+}
+
+static int cps_pm_online_cpu(unsigned int cpu)
+{
+	enum cps_pm_state state;
+	unsigned core = cpu_core(&cpu_data[cpu]);
+	void *entry_fn, *core_rc;
+
+	for (state = CPS_PM_NC_WAIT; state < CPS_PM_STATE_COUNT; state++) {
+		if (per_cpu(nc_asm_enter, core)[state])
+			continue;
+		if (!test_bit(state, state_support))
+			continue;
+
+		entry_fn = cps_gen_entry_code(cpu, state);
+		if (!entry_fn) {
+			pr_err("Failed to generate core %u state %u entry\n",
+			       core, state);
+			clear_bit(state, state_support);
+		}
+
+		per_cpu(nc_asm_enter, core)[state] = entry_fn;
+	}
+
+	if (!per_cpu(ready_count, core)) {
+		core_rc = kmalloc(sizeof(u32), GFP_KERNEL);
+		if (!core_rc) {
+			pr_err("Failed allocate core %u ready_count\n", core);
+			return -ENOMEM;
+		}
+		per_cpu(ready_count, core) = core_rc;
+	}
+
+	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 */
+	if (!mips_cm_present()) {
+		pr_warn("pm-cps: no CM, non-coherent states unavailable\n");
+		return 0;
+	}
+
+	/*
+	 * If interrupts were enabled whilst running a wait instruction on a
+	 * non-coherent core then the VPE may end up processing interrupts
+	 * whilst non-coherent. That would be bad.
+	 */
+	if (cpu_wait == r4k_wait_irqoff)
+		set_bit(CPS_PM_NC_WAIT, state_support);
+	else
+		pr_warn("pm-cps: non-coherent wait unavailable\n");
+
+	/* Detect whether a CPC is present */
+	if (mips_cpc_present()) {
+		/* Detect whether clock gating is implemented */
+		if (read_cpc_cl_stat_conf() & CPC_Cx_STAT_CONF_CLKGAT_IMPL)
+			set_bit(CPS_PM_CLOCK_GATED, state_support);
+		else
+			pr_warn("pm-cps: CPC does not support clock gating\n");
+
+		/* Power gating is available with CPS SMP & any CPC */
+		if (mips_cps_smp_in_use())
+			set_bit(CPS_PM_POWER_GATED, state_support);
+		else
+			pr_warn("pm-cps: CPS SMP not in use, power gating unavailable\n");
+	} else {
+		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);
+}
+arch_initcall(cps_pm_init);