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 <ionela.voinescu@arm.com>
Tested-by: Mian Yousaf Kaukab <ykaukab@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: ionela-voinescu

drivers/acpi/cppc_acpi.c

@@ -413,109 +413,88 @@ static int acpi_get_psd(struct cpc_desc *cpc_ptr, acpi_handle handle)
 	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.
 	 */
-	for_each_possible_cpu(i) {
-		if (cpumask_test_cpu(i, covered_cpus))
-			continue;
-
-		pr = all_cpu_data[i];
-		cpc_ptr = per_cpu(cpc_desc_ptr, i);
-		if (!cpc_ptr) {
-			retval = -EFAULT;
-			goto err_ret;
-		}
+	cpc_ptr = per_cpu(cpc_desc_ptr, cpu);
+	if (!cpc_ptr)
+		return -EFAULT;
 
-		pdomain = &(cpc_ptr->domain_info);
-		cpumask_set_cpu(i, pr->shared_cpu_map);
-		cpumask_set_cpu(i, covered_cpus);
-		if (pdomain->num_processors <= 1)
-			continue;
+	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)
-			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;
-
-		for_each_possible_cpu(j) {
-			if (i == j)
-				continue;
-
-			match_cpc_ptr = per_cpu(cpc_desc_ptr, j);
-			if (!match_cpc_ptr) {
-				retval = -EFAULT;
-				goto err_ret;
-			}
+	/* 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;
 
-			match_pdomain = &(match_cpc_ptr->domain_info);
-			if (match_pdomain->domain != pdomain->domain)
-				continue;
+	for_each_possible_cpu(i) {
+		if (i == cpu)
+			continue;
 
-			/* Here i and j are in the same domain */
-			if (match_pdomain->num_processors != count_target) {
-				retval = -EFAULT;
-				goto err_ret;
-			}
+		match_cpc_ptr = per_cpu(cpc_desc_ptr, i);
+		if (!match_cpc_ptr)
+			goto err_fault;
 
-			if (pdomain->coord_type != match_pdomain->coord_type) {
-				retval = -EFAULT;
-				goto err_ret;
-			}
+		match_pdomain = &(match_cpc_ptr->domain_info);
+		if (match_pdomain->domain != pdomain->domain)
+			continue;
 
-			cpumask_set_cpu(j, covered_cpus);
-			cpumask_set_cpu(j, pr->shared_cpu_map);
-		}
+		/* Here i and cpu are in the same domain */
+		if (match_pdomain->num_processors != count_target)
+			goto err_fault;
 
-		for_each_cpu(j, pr->shared_cpu_map) {
-			if (i == j)
-				continue;
+		if (pdomain->coord_type != match_pdomain->coord_type)
+			goto err_fault;
 
-			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);