[PATCH 6/8] ACPI: CPPC: Factor out cpc_read_reg() and cpc_write_reg()

[Lifeng Zheng]

cppc_get_reg_val() and cppc_set_reg_val() combine two responsibilities:
looking up the per-CPU cpc_desc and then performing the actual register
read/write (including null/optional checks and PCC handling).

Split out the register I/O logic into cpc_read_reg() and cpc_write_reg()
that accept a struct cpc_register_resource pointer directly.  This allows
callers that already hold a register reference -- such as the upcoming
Resource Priority accessors -- to read or write a register without going
through the per-CPU descriptor lookup by index.

Also rename the PCC wrappers from cppc_get/set_reg_val_in_pcc() to
cpc_read/write_in_pcc() to align with the new naming convention.

Signed-off-by: Lifeng Zheng <zhenglifeng1@xxxxxxxxxx>
---
 drivers/acpi/cppc_acpi.c | 89 ++++++++++++++++++++++++++--------------
 1 file changed, 58 insertions(+), 31 deletions(-)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 3f1b61c984d4..0037fca47eea 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -1378,7 +1378,7 @@ static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val)
 	return ret_val;
 }
 
-static int cppc_get_reg_val_in_pcc(int cpu, struct cpc_register_resource *reg, u64 *val)
+static int cpc_read_in_pcc(int cpu, struct cpc_register_resource *reg, u64 *val)
 {
 	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
 	struct cppc_pcc_data *pcc_ss_data = NULL;
@@ -1403,35 +1403,52 @@ static int cppc_get_reg_val_in_pcc(int cpu, struct cpc_register_resource *reg, u
 	return ret;
 }
 
-static int cppc_get_reg_val(int cpu, enum cppc_regs reg_idx, u64 *val)
+/**
+ * cpc_read_reg - Read value from a register element that may be Integer or Buffer.
+ * @cpu: CPU number.
+ * @reg: Pointer to the CPC register element.
+ * @val: Output value.
+ *
+ * Return: 0 on success, -EOPNOTSUPP if null/unsupported, negative on error.
+ */
+static int cpc_read_reg(int cpu, struct cpc_register_resource *reg, u64 *val)
 {
-	struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpu);
-	struct cpc_register_resource *reg;
-
 	if (val == NULL)
 		return -EINVAL;
 
-	if (!cpc_desc) {
-		pr_debug("No CPC descriptor for CPU:%d\n", cpu);
-		return -ENODEV;
-	}
-
-	reg = &cpc_desc->cpc_regs[reg_idx];
-
-	if ((reg->type == ACPI_TYPE_INTEGER && reg->optional &&
-	     !reg->cpc_entry.int_value) || (reg->type != ACPI_TYPE_INTEGER &&
-	     IS_NULL_REG(&reg->cpc_entry.reg))) {
-		pr_debug("CPC register is not supported\n");
-		return -EOPNOTSUPP;
+	if (reg->type == ACPI_TYPE_INTEGER) {
+		if (reg->optional && !reg->cpc_entry.int_value)
+			goto err_unsupported;
+	} else if (reg->type == ACPI_TYPE_BUFFER) {
+		if (IS_NULL_REG(&reg->cpc_entry.reg))
+			goto err_unsupported;
+	} else {
+		goto err_unsupported;
 	}
 
 	if (CPC_IN_PCC(reg))
-		return cppc_get_reg_val_in_pcc(cpu, reg, val);
+		return cpc_read_in_pcc(cpu, reg, val);
 
 	return cpc_read(cpu, reg, val);
+
+err_unsupported:
+	pr_debug("CPC register is not supported\n");
+	return -EOPNOTSUPP;
+}
+
+static int cppc_get_reg_val(int cpu, enum cppc_regs reg_idx, u64 *val)
+{
+	struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpu);
+
+	if (!cpc_desc) {
+		pr_debug("No CPC descriptor for CPU:%d\n", cpu);
+		return -ENODEV;
+	}
+
+	return cpc_read_reg(cpu, &cpc_desc->cpc_regs[reg_idx], val);
 }
 
-static int cppc_set_reg_val_in_pcc(int cpu, struct cpc_register_resource *reg, u64 val)
+static int cpc_write_in_pcc(int cpu, struct cpc_register_resource *reg, u64 val)
 {
 	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
 	struct cppc_pcc_data *pcc_ss_data = NULL;
@@ -1456,18 +1473,16 @@ static int cppc_set_reg_val_in_pcc(int cpu, struct cpc_register_resource *reg, u
 	return ret;
 }
 
-static int cppc_set_reg_val(int cpu, enum cppc_regs reg_idx, u64 val)
+/**
+ * cpc_write_reg - Write a CPC register.
+ * @cpu: CPU number.
+ * @reg: Pointer to the CPC register resource.
+ * @val: Value to write.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+static int cpc_write_reg(int cpu, struct cpc_register_resource *reg, u64 val)
 {
-	struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpu);
-	struct cpc_register_resource *reg;
-
-	if (!cpc_desc) {
-		pr_debug("No CPC descriptor for CPU:%d\n", cpu);
-		return -ENODEV;
-	}
-
-	reg = &cpc_desc->cpc_regs[reg_idx];
-
 	/* if a register is writeable, it must be a buffer and not null */
 	if ((reg->type != ACPI_TYPE_BUFFER) || IS_NULL_REG(&reg->cpc_entry.reg)) {
 		pr_debug("CPC register is not supported\n");
@@ -1475,11 +1490,23 @@ static int cppc_set_reg_val(int cpu, enum cppc_regs reg_idx, u64 val)
 	}
 
 	if (CPC_IN_PCC(reg))
-		return cppc_set_reg_val_in_pcc(cpu, reg, val);
+		return cpc_write_in_pcc(cpu, reg, val);
 
 	return cpc_write(cpu, reg, val);
 }
 
+static int cppc_set_reg_val(int cpu, enum cppc_regs reg_idx, u64 val)
+{
+	struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpu);
+
+	if (!cpc_desc) {
+		pr_debug("No CPC descriptor for CPU:%d\n", cpu);
+		return -ENODEV;
+	}
+
+	return cpc_write_reg(cpu, &cpc_desc->cpc_regs[reg_idx], val);
+}
+
 /**
  * cppc_get_desired_perf - Get the desired performance register value.
  * @cpunum: CPU from which to get desired performance.
-- 
2.33.0