cppc_cpufreq: replace per-cpu data array with a list

The cppc_cpudata per-cpu storage was inefficient (1) additional to causing
functional issues (2) when CPUs are hotplugged out, due to per-cpu data
being improperly initialised.

(1) The amount of information needed for CPPC performance control in its
cpufreq driver depends on the domain (PSD) coordination type:

ANY: One set of CPPC control and capability data (e.g desired
performance, highest/lowest performance, etc) applies to all
CPUs in the domain.

ALL: Same as ANY. To be noted that this type is not currently
supported. When supported, information about which CPUs
belong to a domain is needed in order for frequency change
requests to be sent to each of them.

HW: It's necessary to store CPPC control and capability
information for all the CPUs. HW will then coordinate the
performance state based on their limitations and requests.

NONE: Same as HW. No HW coordination is expected.

Despite this, the previous initialisation code would indiscriminately
allocate memory for all CPUs (all_cpu_data) and unnecessarily
duplicate performance capabilities and the domain sharing mask and type
for each possible CPU.

(2) With the current per-cpu structure, when having ANY coordination,
the cppc_cpudata cpu information is not initialised (will remain 0)
for all CPUs in a policy, other than policy->cpu. When policy->cpu is
hotplugged out, the driver will incorrectly use the uninitialised (0)
value of the other CPUs when making frequency changes. Additionally,
the previous values stored in the perf_ctrls.desired_perf will be
lost when policy->cpu changes.

Therefore replace the array of per cpu data with a list. The memory for
each structure is allocated at policy init, where a single structure
can be allocated per policy, not per cpu. In order to accommodate the
struct list_head node in the cppc_cpudata structure, the now unused cpu
and cur_policy variables are removed.

For example, on a arm64 Juno platform with 6 CPUs: (0, 1, 2, 3) in PSD1,
(4, 5) in PSD2 - ANY coordination, the memory allocation comparison shows:

Before patch:

- ANY coordination:
total slack req alloc/free caller
0 0 0 0/1 _kernel_size_le_hi32+0x0xffff800008ff7810
0 0 0 0/6 _kernel_size_le_hi32+0x0xffff800008ff7808
128 80 48 1/0 _kernel_size_le_hi32+0x0xffff800008ffc070
768 0 768 6/0 _kernel_size_le_hi32+0x0xffff800008ffc0e4

After patch:

- ANY coordination:
total slack req alloc/free caller
256 0 256 2/0 _kernel_size_le_hi32+0x0xffff800008fed410
0 0 0 0/2 _kernel_size_le_hi32+0x0xffff800008fed274

Additional notes:
- A pointer to the policy's cppc_cpudata is stored in policy->driver_data
- Driver registration is skipped if _CPC entries are not present.

Signed-off-by: Ionela Voinescu <[e-mail]>
Tested-by: Mian Yousaf Kaukab <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/acpi/cppc_acpi.c

···
 	return result;
 }
 
+bool acpi_cpc_valid(void)
+{
+	struct cpc_desc *cpc_ptr;
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		cpc_ptr = per_cpu(cpc_desc_ptr, cpu);
+		if (!cpc_ptr)
+			return false;
+	}
+
+	return true;
+}
+EXPORT_SYMBOL_GPL(acpi_cpc_valid);
+
 /**
- * acpi_get_psd_map - Map the CPUs in a common freq domain.
- * @all_cpu_data: Ptrs to CPU specific CPPC data including PSD info.
+ * acpi_get_psd_map - Map the CPUs in the freq domain of a given cpu
+ * @cpu: Find all CPUs that share a domain with cpu.
+ * @cpu_data: Pointer to CPU specific CPPC data including PSD info.
  *
  *	Return: 0 for success or negative value for err.
  */
-int acpi_get_psd_map(struct cppc_cpudata **all_cpu_data)
+int acpi_get_psd_map(unsigned int cpu, struct cppc_cpudata *cpu_data)
 {
-	int count_target;
-	int retval = 0;
-	unsigned int i, j;
-	cpumask_var_t covered_cpus;
-	struct cppc_cpudata *pr, *match_pr;
-	struct acpi_psd_package *pdomain;
-	struct acpi_psd_package *match_pdomain;
 	struct cpc_desc *cpc_ptr, *match_cpc_ptr;
-
-	if (!zalloc_cpumask_var(&covered_cpus, GFP_KERNEL))
-		return -ENOMEM;
+	struct acpi_psd_package *match_pdomain;
+	struct acpi_psd_package *pdomain;
+	int count_target, i;
 
 	/*
 	 * Now that we have _PSD data from all CPUs, let's setup P-state
 	 * domain info.
 	 */
+	cpc_ptr = per_cpu(cpc_desc_ptr, cpu);
+	if (!cpc_ptr)
+		return -EFAULT;
+
+	pdomain = &(cpc_ptr->domain_info);
+	cpumask_set_cpu(cpu, cpu_data->shared_cpu_map);
+	if (pdomain->num_processors <= 1)
+		return 0;
+
+	/* Validate the Domain info */
+	count_target = pdomain->num_processors;
+	if (pdomain->coord_type == DOMAIN_COORD_TYPE_SW_ALL)
+		cpu_data->shared_type = CPUFREQ_SHARED_TYPE_ALL;
+	else if (pdomain->coord_type == DOMAIN_COORD_TYPE_HW_ALL)
+		cpu_data->shared_type = CPUFREQ_SHARED_TYPE_HW;
+	else if (pdomain->coord_type == DOMAIN_COORD_TYPE_SW_ANY)
+		cpu_data->shared_type = CPUFREQ_SHARED_TYPE_ANY;
+
 	for_each_possible_cpu(i) {
-		if (cpumask_test_cpu(i, covered_cpus))
+		if (i == cpu)
 			continue;
 
-		pr = all_cpu_data[i];
-		cpc_ptr = per_cpu(cpc_desc_ptr, i);
-		if (!cpc_ptr) {
-			retval = -EFAULT;
-			goto err_ret;
-		}
+		match_cpc_ptr = per_cpu(cpc_desc_ptr, i);
+		if (!match_cpc_ptr)
+			goto err_fault;
 
-		pdomain = &(cpc_ptr->domain_info);
-		cpumask_set_cpu(i, pr->shared_cpu_map);
-		cpumask_set_cpu(i, covered_cpus);
-		if (pdomain->num_processors <= 1)
+		match_pdomain = &(match_cpc_ptr->domain_info);
+		if (match_pdomain->domain != pdomain->domain)
 			continue;
 
-		/* Validate the Domain info */
-		count_target = pdomain->num_processors;
-		if (pdomain->coord_type == DOMAIN_COORD_TYPE_SW_ALL)
-			pr->shared_type = CPUFREQ_SHARED_TYPE_ALL;
-		else if (pdomain->coord_type == DOMAIN_COORD_TYPE_HW_ALL)
-			pr->shared_type = CPUFREQ_SHARED_TYPE_HW;
-		else if (pdomain->coord_type == DOMAIN_COORD_TYPE_SW_ANY)
-			pr->shared_type = CPUFREQ_SHARED_TYPE_ANY;
+		/* Here i and cpu are in the same domain */
+		if (match_pdomain->num_processors != count_target)
+			goto err_fault;
 
-		for_each_possible_cpu(j) {
-			if (i == j)
-				continue;
+		if (pdomain->coord_type != match_pdomain->coord_type)
+			goto err_fault;
 
-			match_cpc_ptr = per_cpu(cpc_desc_ptr, j);
-			if (!match_cpc_ptr) {
-				retval = -EFAULT;
-				goto err_ret;
-			}
-
-			match_pdomain = &(match_cpc_ptr->domain_info);
-			if (match_pdomain->domain != pdomain->domain)
-				continue;
-
-			/* Here i and j are in the same domain */
-			if (match_pdomain->num_processors != count_target) {
-				retval = -EFAULT;
-				goto err_ret;
-			}
-
-			if (pdomain->coord_type != match_pdomain->coord_type) {
-				retval = -EFAULT;
-				goto err_ret;
-			}
-
-			cpumask_set_cpu(j, covered_cpus);
-			cpumask_set_cpu(j, pr->shared_cpu_map);
-		}
-
-		for_each_cpu(j, pr->shared_cpu_map) {
-			if (i == j)
-				continue;
-
-			match_pr = all_cpu_data[j];
-			match_pr->shared_type = pr->shared_type;
-			cpumask_copy(match_pr->shared_cpu_map,
-				     pr->shared_cpu_map);
-		}
+		cpumask_set_cpu(i, cpu_data->shared_cpu_map);
 	}
-	goto out;
 
-err_ret:
-	for_each_possible_cpu(i) {
-		pr = all_cpu_data[i];
+	return 0;
 
-		/* Assume no coordination on any error parsing domain info */
-		cpumask_clear(pr->shared_cpu_map);
-		cpumask_set_cpu(i, pr->shared_cpu_map);
-		pr->shared_type = CPUFREQ_SHARED_TYPE_NONE;
-	}
-out:
-	free_cpumask_var(covered_cpus);
-	return retval;
+err_fault:
+	/* Assume no coordination on any error parsing domain info */
+	cpumask_clear(cpu_data->shared_cpu_map);
+	cpumask_set_cpu(cpu, cpu_data->shared_cpu_map);
+	cpu_data->shared_type = CPUFREQ_SHARED_TYPE_NONE;
+
+	return -EFAULT;
 }
 EXPORT_SYMBOL_GPL(acpi_get_psd_map);
 

drivers/cpufreq/cppc_cpufreq.c

···
 #define DMI_PROCESSOR_MAX_SPEED		0x14
 
 /*
- * These structs contain information parsed from per CPU
- * ACPI _CPC structures.
- * e.g. For each CPU the highest, lowest supported
- * performance capabilities, desired performance level
- * requested etc.
+ * This list contains information parsed from per CPU ACPI _CPC and _PSD
+ * structures: e.g. the highest and lowest supported performance, capabilities,
+ * desired performance, level requested etc. Depending on the share_type, not
+ * all CPUs will have an entry in the list.
  */
-static struct cppc_cpudata **all_cpu_data;
+static LIST_HEAD(cpu_data_list);
+
 static bool boost_supported;
 
 struct cppc_workaround_oem_info {
···
 static int cppc_cpufreq_set_target(struct cpufreq_policy *policy,
 				   unsigned int target_freq,
 				   unsigned int relation)
+
 {
-	struct cppc_cpudata *cpu_data = all_cpu_data[policy->cpu];
+	struct cppc_cpudata *cpu_data = policy->driver_data;
 	unsigned int cpu = policy->cpu;
 	struct cpufreq_freqs freqs;
 	u32 desired_perf;
···
 
 static void cppc_cpufreq_stop_cpu(struct cpufreq_policy *policy)
 {
-	struct cppc_cpudata *cpu_data = all_cpu_data[policy->cpu];
+	struct cppc_cpudata *cpu_data = policy->driver_data;
 	struct cppc_perf_caps *caps = &cpu_data->perf_caps;
 	unsigned int cpu = policy->cpu;
 	int ret;
···
 	if (ret)
 		pr_debug("Err setting perf value:%d on CPU:%d. ret:%d\n",
 			 caps->lowest_perf, cpu, ret);
+
+	/* Remove CPU node from list and free driver data for policy */
+	free_cpumask_var(cpu_data->shared_cpu_map);
+	list_del(&cpu_data->node);
+	kfree(policy->driver_data);
+	policy->driver_data = NULL;
 }
 
 /*
···
 }
 #endif
 
-static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
+
+static struct cppc_cpudata *cppc_cpufreq_get_cpu_data(unsigned int cpu)
 {
-	struct cppc_cpudata *cpu_data = all_cpu_data[policy->cpu];
-	struct cppc_perf_caps *caps = &cpu_data->perf_caps;
-	unsigned int cpu = policy->cpu;
-	int i, ret = 0;
+	struct cppc_cpudata *cpu_data;
+	int ret;
 
-	cpu_data->cpu = cpu;
-	ret = cppc_get_perf_caps(cpu, caps);
+	cpu_data = kzalloc(sizeof(struct cppc_cpudata), GFP_KERNEL);
+	if (!cpu_data)
+		goto out;
 
+	if (!zalloc_cpumask_var(&cpu_data->shared_cpu_map, GFP_KERNEL))
+		goto free_cpu;
+
+	ret = acpi_get_psd_map(cpu, cpu_data);
 	if (ret) {
-		pr_debug("Err reading CPU%d perf capabilities. ret:%d\n",
-			 cpu, ret);
-		return ret;
+		pr_debug("Err parsing CPU%d PSD data: ret:%d\n", cpu, ret);
+		goto free_mask;
+	}
+
+	ret = cppc_get_perf_caps(cpu, &cpu_data->perf_caps);
+	if (ret) {
+		pr_debug("Err reading CPU%d perf caps: ret:%d\n", cpu, ret);
+		goto free_mask;
 	}
 
 	/* Convert the lowest and nominal freq from MHz to KHz */
-	caps->lowest_freq *= 1000;
-	caps->nominal_freq *= 1000;
+	cpu_data->perf_caps.lowest_freq *= 1000;
+	cpu_data->perf_caps.nominal_freq *= 1000;
+
+	list_add(&cpu_data->node, &cpu_data_list);
+
+	return cpu_data;
+
+free_mask:
+	free_cpumask_var(cpu_data->shared_cpu_map);
+free_cpu:
+	kfree(cpu_data);
+out:
+	return NULL;
+}
+
+static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
+{
+	unsigned int cpu = policy->cpu;
+	struct cppc_cpudata *cpu_data;
+	struct cppc_perf_caps *caps;
+	int ret;
+
+	cpu_data = cppc_cpufreq_get_cpu_data(cpu);
+	if (!cpu_data) {
+		pr_err("Error in acquiring _CPC/_PSD data for CPU%d.\n", cpu);
+		return -ENODEV;
+	}
+	caps = &cpu_data->perf_caps;
+	policy->driver_data = cpu_data;
 
 	/*
 	 * Set min to lowest nonlinear perf to avoid any efficiency penalty (see
···
 		/* Nothing to be done - we'll have a policy for each CPU */
 		break;
 	case CPUFREQ_SHARED_TYPE_ANY:
-		 /* All CPUs in the domain will share a policy */
+		/*
+		 * All CPUs in the domain will share a policy and all cpufreq
+		 * operations will use a single cppc_cpudata structure stored
+		 * in policy->driver_data.
+		 */
 		cpumask_copy(policy->cpus, cpu_data->shared_cpu_map);
-
-		for_each_cpu(i, policy->cpus) {
-			if (unlikely(i == cpu))
-				continue;
-
-			memcpy(&all_cpu_data[i]->perf_caps, caps,
-			       sizeof(cpu_data->perf_caps));
-		}
 		break;
 	default:
 		pr_debug("Unsupported CPU co-ord type: %d\n",
 			 policy->shared_type);
 		return -EFAULT;
 	}
-
-	cpu_data->cur_policy = policy;
 
 	/*
 	 * If 'highest_perf' is greater than 'nominal_perf', we assume CPU Boost
···
 static unsigned int cppc_cpufreq_get_rate(unsigned int cpu)
 {
 	struct cppc_perf_fb_ctrs fb_ctrs_t0 = {0}, fb_ctrs_t1 = {0};
-	struct cppc_cpudata *cpu_data = all_cpu_data[cpu];
+	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
+	struct cppc_cpudata *cpu_data = policy->driver_data;
 	int ret;
+
+	cpufreq_cpu_put(policy);
 
 	ret = cppc_get_perf_ctrs(cpu, &fb_ctrs_t0);
 	if (ret)
···
 
 static int cppc_cpufreq_set_boost(struct cpufreq_policy *policy, int state)
 {
-	struct cppc_cpudata *cpu_data = all_cpu_data[policy->cpu];
+	struct cppc_cpudata *cpu_data = policy->driver_data;
 	struct cppc_perf_caps *caps = &cpu_data->perf_caps;
 	int ret;
 
···
 
 static ssize_t show_freqdomain_cpus(struct cpufreq_policy *policy, char *buf)
 {
-	unsigned int cpu = policy->cpu;
+	struct cppc_cpudata *cpu_data = policy->driver_data;
 
-	return cpufreq_show_cpus(all_cpu_data[cpu]->shared_cpu_map, buf);
+	return cpufreq_show_cpus(cpu_data->shared_cpu_map, buf);
 }
 cpufreq_freq_attr_ro(freqdomain_cpus);
 
···
  */
 static unsigned int hisi_cppc_cpufreq_get_rate(unsigned int cpu)
 {
-	struct cppc_cpudata *cpu_data = all_cpu_data[cpu];
+	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
+	struct cppc_cpudata *cpu_data = policy->driver_data;
 	u64 desired_perf;
 	int ret;
+
+	cpufreq_cpu_put(policy);
 
 	ret = cppc_get_desired_perf(cpu, &desired_perf);
 	if (ret < 0)
···
 
 static int __init cppc_cpufreq_init(void)
 {
-	struct cppc_cpudata *cpu_data;
-	int i, ret = 0;
-
-	if (acpi_disabled)
+	if ((acpi_disabled) || !acpi_cpc_valid())
 		return -ENODEV;
 
-	all_cpu_data = kcalloc(num_possible_cpus(), sizeof(void *),
-			       GFP_KERNEL);
-	if (!all_cpu_data)
-		return -ENOMEM;
-
-	for_each_possible_cpu(i) {
-		all_cpu_data[i] = kzalloc(sizeof(struct cppc_cpudata), GFP_KERNEL);
-		if (!all_cpu_data[i])
-			goto out;
-
-		cpu_data = all_cpu_data[i];
-		if (!zalloc_cpumask_var(&cpu_data->shared_cpu_map, GFP_KERNEL))
-			goto out;
-	}
-
-	ret = acpi_get_psd_map(all_cpu_data);
-	if (ret) {
-		pr_debug("Error parsing PSD data. Aborting cpufreq registration.\n");
-		goto out;
-	}
+	INIT_LIST_HEAD(&cpu_data_list);
 
 	cppc_check_hisi_workaround();
 
-	ret = cpufreq_register_driver(&cppc_cpufreq_driver);
-	if (ret)
-		goto out;
+	return cpufreq_register_driver(&cppc_cpufreq_driver);
+}
 
-	return ret;
+static inline void free_cpu_data(void)
+{
+	struct cppc_cpudata *iter, *tmp;
 
-out:
-	for_each_possible_cpu(i) {
-		cpu_data = all_cpu_data[i];
-		if (!cpu_data)
-			break;
-		free_cpumask_var(cpu_data->shared_cpu_map);
-		kfree(cpu_data);
+	list_for_each_entry_safe(iter, tmp, &cpu_data_list, node) {
+		free_cpumask_var(iter->shared_cpu_map);
+		list_del(&iter->node);
+		kfree(iter);
 	}
 
-	kfree(all_cpu_data);
-	return -ENODEV;
 }
 
 static void __exit cppc_cpufreq_exit(void)
 {
-	struct cppc_cpudata *cpu_data;
-	int i;
-
 	cpufreq_unregister_driver(&cppc_cpufreq_driver);
 
-	for_each_possible_cpu(i) {
-		cpu_data = all_cpu_data[i];
-		free_cpumask_var(cpu_data->shared_cpu_map);
-		kfree(cpu_data);
-	}
-
-	kfree(all_cpu_data);
+	free_cpu_data();
 }
 
 module_exit(cppc_cpufreq_exit);

include/acpi/cppc_acpi.h

···
 
 /* Per CPU container for runtime CPPC management. */
 struct cppc_cpudata {
-	int cpu;
+	struct list_head node;
 	struct cppc_perf_caps perf_caps;
 	struct cppc_perf_ctrls perf_ctrls;
 	struct cppc_perf_fb_ctrs perf_fb_ctrs;
-	struct cpufreq_policy *cur_policy;
 	unsigned int shared_type;
 	cpumask_var_t shared_cpu_map;
 };
···
 extern int cppc_get_perf_ctrs(int cpu, struct cppc_perf_fb_ctrs *perf_fb_ctrs);
 extern int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls);
 extern int cppc_get_perf_caps(int cpu, struct cppc_perf_caps *caps);
-extern int acpi_get_psd_map(struct cppc_cpudata **);
+extern bool acpi_cpc_valid(void);
+extern int acpi_get_psd_map(unsigned int cpu, struct cppc_cpudata *cpu_data);
 extern unsigned int cppc_get_transition_latency(int cpu);
 extern bool cpc_ffh_supported(void);
 extern int cpc_read_ffh(int cpunum, struct cpc_reg *reg, u64 *val);