ACPI / CPPC: Add support for CPPC v3

CPPC V3 introduces two new entries to make it easier to convert between
abstract processor performance and frequency. The two new entries are
lowest frequency and nominal frequency. These are the frequencies
corresponding to lowest and nominal abstract performance.

Add support to read the new entries and populate them as part of the
CPPC performance capabilities which can be used by cpufreq drivers

Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/cppc_acpi.c

@@ -156,6 +156,9 @@ show_cppc_data(cppc_get_perf_caps, cppc_perf_caps, highest_perf);
 show_cppc_data(cppc_get_perf_caps, cppc_perf_caps, lowest_perf);
 show_cppc_data(cppc_get_perf_caps, cppc_perf_caps, nominal_perf);
 show_cppc_data(cppc_get_perf_caps, cppc_perf_caps, lowest_nonlinear_perf);
+show_cppc_data(cppc_get_perf_caps, cppc_perf_caps, lowest_freq);
+show_cppc_data(cppc_get_perf_caps, cppc_perf_caps, nominal_freq);
+
 show_cppc_data(cppc_get_perf_ctrs, cppc_perf_fb_ctrs, reference_perf);
 show_cppc_data(cppc_get_perf_ctrs, cppc_perf_fb_ctrs, wraparound_time);
 
@@ -183,6 +186,8 @@ static struct attribute *cppc_attrs[] = {
 	&lowest_perf.attr,
 	&lowest_nonlinear_perf.attr,
 	&nominal_perf.attr,
+	&nominal_freq.attr,
+	&lowest_freq.attr,
 	NULL
 };
 
@@ -613,7 +618,6 @@ bool __weak cpc_ffh_supported(void)
 	return false;
 }
 
-
 /**
  * pcc_data_alloc() - Allocate the pcc_data memory for pcc subspace
  *
@@ -641,6 +645,34 @@ int pcc_data_alloc(int pcc_ss_id)
 
 	return 0;
 }
+
+/* Check if CPPC revision + num_ent combination is supported */
+static bool is_cppc_supported(int revision, int num_ent)
+{
+	int expected_num_ent;
+
+	switch (revision) {
+	case CPPC_V2_REV:
+		expected_num_ent = CPPC_V2_NUM_ENT;
+		break;
+	case CPPC_V3_REV:
+		expected_num_ent = CPPC_V3_NUM_ENT;
+		break;
+	default:
+		pr_debug("Firmware exports unsupported CPPC revision: %d\n",
+			revision);
+		return false;
+	}
+
+	if (expected_num_ent != num_ent) {
+		pr_debug("Firmware exports %d entries. Expected: %d for CPPC rev:%d\n",
+			num_ent, expected_num_ent, revision);
+		return false;
+	}
+
+	return true;
+}
+
 /*
  * An example CPC table looks like the following.
  *
@@ -731,14 +763,6 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
 				cpc_obj->type);
 		goto out_free;
 	}
-
-	/* Only support CPPCv2. Bail otherwise. */
-	if (num_ent != CPPC_NUM_ENT) {
-		pr_debug("Firmware exports %d entries. Expected: %d\n",
-				num_ent, CPPC_NUM_ENT);
-		goto out_free;
-	}
-
 	cpc_ptr->num_entries = num_ent;
 
 	/* Second entry should be revision. */
@@ -750,12 +774,10 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
 				cpc_obj->type);
 		goto out_free;
 	}
+	cpc_ptr->version = cpc_rev;
 
-	if (cpc_rev != CPPC_REV) {
-		pr_debug("Firmware exports revision:%d. Expected:%d\n",
-				cpc_rev, CPPC_REV);
+	if (!is_cppc_supported(cpc_rev, num_ent))
 		goto out_free;
-	}
 
 	/* Iterate through remaining entries in _CPC */
 	for (i = 2; i < num_ent; i++) {
@@ -808,6 +830,18 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
 		}
 	}
 	per_cpu(cpu_pcc_subspace_idx, pr->id) = pcc_subspace_id;
+
+	/*
+	 * Initialize the remaining cpc_regs as unsupported.
+	 * Example: In case FW exposes CPPC v2, the below loop will initialize
+	 * LOWEST_FREQ and NOMINAL_FREQ regs as unsupported
+	 */
+	for (i = num_ent - 2; i < MAX_CPC_REG_ENT; i++) {
+		cpc_ptr->cpc_regs[i].type = ACPI_TYPE_INTEGER;
+		cpc_ptr->cpc_regs[i].cpc_entry.int_value = 0;
+	}
+
+
 	/* Store CPU Logical ID */
 	cpc_ptr->cpu_id = pr->id;
 
@@ -1037,8 +1071,9 @@ int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps)
 {
 	struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpunum);
 	struct cpc_register_resource *highest_reg, *lowest_reg,
-		*lowest_non_linear_reg, *nominal_reg;
-	u64 high, low, nom, min_nonlinear;
+		*lowest_non_linear_reg, *nominal_reg,
+		*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;
 	int ret = 0, regs_in_pcc = 0;
@@ -1053,10 +1088,13 @@ int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps)
 	lowest_reg = &cpc_desc->cpc_regs[LOWEST_PERF];
 	lowest_non_linear_reg = &cpc_desc->cpc_regs[LOW_NON_LINEAR_PERF];
 	nominal_reg = &cpc_desc->cpc_regs[NOMINAL_PERF];
+	low_freq_reg = &cpc_desc->cpc_regs[LOWEST_FREQ];
+	nom_freq_reg = &cpc_desc->cpc_regs[NOMINAL_FREQ];
 
 	/* Are any of the regs PCC ?*/
 	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(lowest_non_linear_reg) || CPC_IN_PCC(nominal_reg) ||
+		CPC_IN_PCC(low_freq_reg) || CPC_IN_PCC(nom_freq_reg)) {
 		regs_in_pcc = 1;
 		down_write(&pcc_ss_data->pcc_lock);
 		/* Ring doorbell once to update PCC subspace */
@@ -1081,6 +1119,17 @@ int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps)
 	if (!high || !low || !nom || !min_nonlinear)
 		ret = -EFAULT;
 
+	/* Read optional lowest and nominal frequencies if present */
+	if (CPC_SUPPORTED(low_freq_reg))
+		cpc_read(cpunum, low_freq_reg, &low_f);
+
+	if (CPC_SUPPORTED(nom_freq_reg))
+		cpc_read(cpunum, nom_freq_reg, &nom_f);
+
+	perf_caps->lowest_freq = low_f;
+	perf_caps->nominal_freq = nom_f;
+
+
 out_err:
 	if (regs_in_pcc)
 		up_write(&pcc_ss_data->pcc_lock);

include/acpi/cppc_acpi.h

@@ -20,14 +20,16 @@
 #include <acpi/pcc.h>
 #include <acpi/processor.h>
 
-/* Only support CPPCv2 for now. */
-#define CPPC_NUM_ENT	21
-#define CPPC_REV	2
+/* Support CPPCv2 and CPPCv3  */
+#define CPPC_V2_REV	2
+#define CPPC_V3_REV	3
+#define CPPC_V2_NUM_ENT	21
+#define CPPC_V3_NUM_ENT	23
 
 #define PCC_CMD_COMPLETE_MASK	(1 << 0)
 #define PCC_ERROR_MASK		(1 << 2)
 
-#define MAX_CPC_REG_ENT 19
+#define MAX_CPC_REG_ENT 21
 
 /* CPPC specific PCC commands. */
 #define	CMD_READ 0
@@ -91,6 +93,8 @@ enum cppc_regs {
 	AUTO_ACT_WINDOW,
 	ENERGY_PERF,
 	REFERENCE_PERF,
+	LOWEST_FREQ,
+	NOMINAL_FREQ,
 };
 
 /*
@@ -104,6 +108,8 @@ struct cppc_perf_caps {
 	u32 nominal_perf;
 	u32 lowest_perf;
 	u32 lowest_nonlinear_perf;
+	u32 lowest_freq;
+	u32 nominal_freq;
 };
 
 struct cppc_perf_ctrls {