cstate.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2005 Intel Corporation
 * 	Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
 * 	- Added _PDC for SMP C-states on Intel CPUs
 */

#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/init.h>
#include <linux/acpi.h>
#include <linux/cpu.h>
#include <linux/sched.h>

#include <acpi/processor.h>
#include <asm/mwait.h>
#include <asm/special_insns.h>

/*
 * Initialize bm_flags based on the CPU cache properties
 * On SMP it depends on cache configuration
 * - When cache is not shared among all CPUs, we flush cache
 *   before entering C3.
 * - When cache is shared among all CPUs, we use bm_check
 *   mechanism as in UP case
 *
 * This routine is called only after all the CPUs are online
 */
void acpi_processor_power_init_bm_check(struct acpi_processor_flags *flags,
					unsigned int cpu)
{
	struct cpuinfo_x86 *c = &cpu_data(cpu);

	flags->bm_check = 0;
	if (num_online_cpus() == 1)
		flags->bm_check = 1;
	else if (c->x86_vendor == X86_VENDOR_INTEL) {
		/*
		 * Today all MP CPUs that support C3 share cache.
		 * And caches should not be flushed by software while
		 * entering C3 type state.
		 */
		flags->bm_check = 1;
	}

	/*
	 * On all recent Intel platforms, ARB_DISABLE is a nop.
	 * So, set bm_control to zero to indicate that ARB_DISABLE
	 * is not required while entering C3 type state on
	 * P4, Core and beyond CPUs
	 */
	if (c->x86_vendor == X86_VENDOR_INTEL &&
	    (c->x86 > 0xf || (c->x86 == 6 && c->x86_model >= 0x0f)))
			flags->bm_control = 0;
	/*
	 * For all recent Centaur CPUs, the ucode will make sure that each
	 * core can keep cache coherence with each other while entering C3
	 * type state. So, set bm_check to 1 to indicate that the kernel
	 * doesn't need to execute a cache flush operation (WBINVD) when
	 * entering C3 type state.
	 */
	if (c->x86_vendor == X86_VENDOR_CENTAUR) {
		if (c->x86 > 6 || (c->x86 == 6 && c->x86_model == 0x0f &&
		    c->x86_stepping >= 0x0e))
			flags->bm_check = 1;
	}

	if (c->x86_vendor == X86_VENDOR_ZHAOXIN) {
		/*
		 * All Zhaoxin CPUs that support C3 share cache.
		 * And caches should not be flushed by software while
		 * entering C3 type state.
		 */
		flags->bm_check = 1;
		/*
		 * On all recent Zhaoxin platforms, ARB_DISABLE is a nop.
		 * So, set bm_control to zero to indicate that ARB_DISABLE
		 * is not required while entering C3 type state.
		 */
		flags->bm_control = 0;
	}
	if (c->x86_vendor == X86_VENDOR_AMD && c->x86 >= 0x17) {
		/*
		 * For all AMD Zen or newer CPUs that support C3, caches
		 * should not be flushed by software while entering C3
		 * type state. Set bm->check to 1 so that kernel doesn't
		 * need to execute cache flush operation.
		 */
		flags->bm_check = 1;
		/*
		 * In current AMD C state implementation ARB_DIS is no longer
		 * used. So set bm_control to zero to indicate ARB_DIS is not
		 * required while entering C3 type state.
		 */
		flags->bm_control = 0;
	}
}
EXPORT_SYMBOL(acpi_processor_power_init_bm_check);

/* The code below handles cstate entry with monitor-mwait pair on Intel*/

struct cstate_entry {
	struct {
		unsigned int eax;
		unsigned int ecx;
	} states[ACPI_PROCESSOR_MAX_POWER];
};
static struct cstate_entry __percpu *cpu_cstate_entry;	/* per CPU ptr */

static short mwait_supported[ACPI_PROCESSOR_MAX_POWER];

#define NATIVE_CSTATE_BEYOND_HALT	(2)

static long acpi_processor_ffh_cstate_probe_cpu(void *_cx)
{
	struct acpi_processor_cx *cx = _cx;
	long retval;
	unsigned int eax, ebx, ecx, edx;
	unsigned int edx_part;
	unsigned int cstate_type; /* C-state type and not ACPI C-state type */
	unsigned int num_cstate_subtype;

	cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);

	/* Check whether this particular cx_type (in CST) is supported or not */
	cstate_type = ((cx->address >> MWAIT_SUBSTATE_SIZE) &
			MWAIT_CSTATE_MASK) + 1;
	edx_part = edx >> (cstate_type * MWAIT_SUBSTATE_SIZE);
	num_cstate_subtype = edx_part & MWAIT_SUBSTATE_MASK;

	retval = 0;
	/* If the HW does not support any sub-states in this C-state */
	if (num_cstate_subtype == 0) {
		pr_warn(FW_BUG "ACPI MWAIT C-state 0x%x not supported by HW (0x%x)\n",
				cx->address, edx_part);
		retval = -1;
		goto out;
	}

	/* mwait ecx extensions INTERRUPT_BREAK should be supported for C2/C3 */
	if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
	    !(ecx & CPUID5_ECX_INTERRUPT_BREAK)) {
		retval = -1;
		goto out;
	}

	if (!mwait_supported[cstate_type]) {
		mwait_supported[cstate_type] = 1;
		printk(KERN_DEBUG
			"Monitor-Mwait will be used to enter C-%d state\n",
			cx->type);
	}
	snprintf(cx->desc,
			ACPI_CX_DESC_LEN, "ACPI FFH MWAIT 0x%x",
			cx->address);
out:
	return retval;
}

int acpi_processor_ffh_cstate_probe(unsigned int cpu,
		struct acpi_processor_cx *cx, struct acpi_power_register *reg)
{
	struct cstate_entry *percpu_entry;
	struct cpuinfo_x86 *c = &cpu_data(cpu);
	long retval;

	if (!cpu_cstate_entry || c->cpuid_level < CPUID_MWAIT_LEAF)
		return -1;

	if (reg->bit_offset != NATIVE_CSTATE_BEYOND_HALT)
		return -1;

	percpu_entry = per_cpu_ptr(cpu_cstate_entry, cpu);
	percpu_entry->states[cx->index].eax = 0;
	percpu_entry->states[cx->index].ecx = 0;

	/* Make sure we are running on right CPU */

	retval = call_on_cpu(cpu, acpi_processor_ffh_cstate_probe_cpu, cx,
			     false);
	if (retval == 0) {
		/* Use the hint in CST */
		percpu_entry->states[cx->index].eax = cx->address;
		percpu_entry->states[cx->index].ecx = MWAIT_ECX_INTERRUPT_BREAK;
	}

	/*
	 * For _CST FFH on Intel, if GAS.access_size bit 1 is cleared,
	 * then we should skip checking BM_STS for this C-state.
	 * ref: "Intel Processor Vendor-Specific ACPI Interface Specification"
	 */
	if ((c->x86_vendor == X86_VENDOR_INTEL) && !(reg->access_size & 0x2))
		cx->bm_sts_skip = 1;

	return retval;
}
EXPORT_SYMBOL_GPL(acpi_processor_ffh_cstate_probe);

void __cpuidle acpi_processor_ffh_cstate_enter(struct acpi_processor_cx *cx)
{
	unsigned int cpu = smp_processor_id();
	struct cstate_entry *percpu_entry;

	percpu_entry = per_cpu_ptr(cpu_cstate_entry, cpu);
	mwait_idle_with_hints(percpu_entry->states[cx->index].eax,
	                      percpu_entry->states[cx->index].ecx);
}
EXPORT_SYMBOL_GPL(acpi_processor_ffh_cstate_enter);

static int __init ffh_cstate_init(void)
{
	struct cpuinfo_x86 *c = &boot_cpu_data;

	if (c->x86_vendor != X86_VENDOR_INTEL &&
	    c->x86_vendor != X86_VENDOR_AMD &&
	    c->x86_vendor != X86_VENDOR_HYGON)
		return -1;

	cpu_cstate_entry = alloc_percpu(struct cstate_entry);
	return 0;
}

static void __exit ffh_cstate_exit(void)
{
	free_percpu(cpu_cstate_entry);
	cpu_cstate_entry = NULL;
}

arch_initcall(ffh_cstate_init);
__exitcall(ffh_cstate_exit);