ACPI / CPPC: Check for valid PCC subspace only if PCC is used

Changes the behavior where we return error if there are no valid PCC
subspace for a given performance domain.

The ACPI spec does not mandate the use PCC, so it is possible to have
platforms where a PCC subspace may not be present, so we need to check
for a valid PCC subspace ID only if the register is a PCC register.
Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/cppc_acpi.c

@@ -1075,15 +1075,14 @@ int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps)
 		*low_freq_reg = NULL, *nom_freq_reg = NULL;
 	u64 high, low, nom, min_nonlinear, low_f = 0, nom_f = 0;
 	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpunum);
-	struct cppc_pcc_data *pcc_ss_data;
+	struct cppc_pcc_data *pcc_ss_data = NULL;
 	int ret = 0, regs_in_pcc = 0;
 
-	if (!cpc_desc || pcc_ss_id < 0) {
+	if (!cpc_desc) {
 		pr_debug("No CPC descriptor for CPU:%d\n", cpunum);
 		return -ENODEV;
 	}
 
-	pcc_ss_data = pcc_data[pcc_ss_id];
 	highest_reg = &cpc_desc->cpc_regs[HIGHEST_PERF];
 	lowest_reg = &cpc_desc->cpc_regs[LOWEST_PERF];
 	lowest_non_linear_reg = &cpc_desc->cpc_regs[LOW_NON_LINEAR_PERF];
@@ -1095,6 +1094,11 @@ int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps)
 	if (CPC_IN_PCC(highest_reg) || CPC_IN_PCC(lowest_reg) ||
 		CPC_IN_PCC(lowest_non_linear_reg) || CPC_IN_PCC(nominal_reg) ||
 		CPC_IN_PCC(low_freq_reg) || CPC_IN_PCC(nom_freq_reg)) {
+		if (pcc_ss_id < 0) {
+			pr_debug("Invalid pcc_ss_id\n");
+			return -ENODEV;
+		}
+		pcc_ss_data = pcc_data[pcc_ss_id];
 		regs_in_pcc = 1;
 		down_write(&pcc_ss_data->pcc_lock);
 		/* Ring doorbell once to update PCC subspace */
@@ -1150,16 +1154,15 @@ int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs)
 	struct cpc_register_resource *delivered_reg, *reference_reg,
 		*ref_perf_reg, *ctr_wrap_reg;
 	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpunum);
-	struct cppc_pcc_data *pcc_ss_data;
+	struct cppc_pcc_data *pcc_ss_data = NULL;
 	u64 delivered, reference, ref_perf, ctr_wrap_time;
 	int ret = 0, regs_in_pcc = 0;
 
-	if (!cpc_desc || pcc_ss_id < 0) {
+	if (!cpc_desc) {
 		pr_debug("No CPC descriptor for CPU:%d\n", cpunum);
 		return -ENODEV;
 	}
 
-	pcc_ss_data = pcc_data[pcc_ss_id];
 	delivered_reg = &cpc_desc->cpc_regs[DELIVERED_CTR];
 	reference_reg = &cpc_desc->cpc_regs[REFERENCE_CTR];
 	ref_perf_reg = &cpc_desc->cpc_regs[REFERENCE_PERF];
@@ -1175,6 +1178,11 @@ int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs)
 	/* Are any of the regs PCC ?*/
 	if (CPC_IN_PCC(delivered_reg) || CPC_IN_PCC(reference_reg) ||
 		CPC_IN_PCC(ctr_wrap_reg) || CPC_IN_PCC(ref_perf_reg)) {
+		if (pcc_ss_id < 0) {
+			pr_debug("Invalid pcc_ss_id\n");
+			return -ENODEV;
+		}
+		pcc_ss_data = pcc_data[pcc_ss_id];
 		down_write(&pcc_ss_data->pcc_lock);
 		regs_in_pcc = 1;
 		/* Ring doorbell once to update PCC subspace */
@@ -1225,15 +1233,14 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
 	struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpu);
 	struct cpc_register_resource *desired_reg;
 	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
-	struct cppc_pcc_data *pcc_ss_data;
+	struct cppc_pcc_data *pcc_ss_data = NULL;
 	int ret = 0;
 
-	if (!cpc_desc || pcc_ss_id < 0) {
+	if (!cpc_desc) {
 		pr_debug("No CPC descriptor for CPU:%d\n", cpu);
 		return -ENODEV;
 	}
 
-	pcc_ss_data = pcc_data[pcc_ss_id];
 	desired_reg = &cpc_desc->cpc_regs[DESIRED_PERF];
 
 	/*
@@ -1244,6 +1251,11 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
 	 * achieve that goal here
 	 */
 	if (CPC_IN_PCC(desired_reg)) {
+		if (pcc_ss_id < 0) {
+			pr_debug("Invalid pcc_ss_id\n");
+			return -ENODEV;
+		}
+		pcc_ss_data = pcc_data[pcc_ss_id];
 		down_read(&pcc_ss_data->pcc_lock); /* BEGIN Phase-I */
 		if (pcc_ss_data->platform_owns_pcc) {
 			ret = check_pcc_chan(pcc_ss_id, false);