[PATCH v5 2/8] ACPI: CPPC: Optimize cppc_get_perf()

[Lifeng Zheng <zhenglifeng1@xxxxxxxxxx>]

Optimize cppc_get_perf() with three changes:

1. Change the error kind to "no such device" when pcc_ss_id < 0, as other
register value getting functions.

2. Add a check to verify if the register is a mandatory or cpc supported
one before using it.

3. Return the result of cpc_read() instead of 0.

Signed-off-by: Lifeng Zheng <zhenglifeng1@xxxxxxxxxx>
---
 drivers/acpi/cppc_acpi.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 39f019e265da..db22f8f107db 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -1201,20 +1201,27 @@ static int cppc_get_perf(int cpunum, enum cppc_regs reg_idx, u64 *perf)
 
 	reg = &cpc_desc->cpc_regs[reg_idx];
 
+	if (IS_OPTIONAL_CPC_REG(reg_idx) && !CPC_SUPPORTED(reg)) {
+		pr_debug("CPC register (reg_idx=%d) is not supported\n", reg_idx);
+		return -EOPNOTSUPP;
+	}
+
 	if (CPC_IN_PCC(reg)) {
 		int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpunum);
 		struct cppc_pcc_data *pcc_ss_data = NULL;
-		int ret = 0;
+		int ret;
 
-		if (pcc_ss_id < 0)
-			return -EIO;
+		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);
 
 		if (send_pcc_cmd(pcc_ss_id, CMD_READ) >= 0)
-			cpc_read(cpunum, reg, perf);
+			ret = cpc_read(cpunum, reg, perf);
 		else
 			ret = -EIO;
 
@@ -1223,9 +1230,7 @@ static int cppc_get_perf(int cpunum, enum cppc_regs reg_idx, u64 *perf)
 		return ret;
 	}
 
-	cpc_read(cpunum, reg, perf);
-
-	return 0;
+	return cpc_read(cpunum, reg, perf);
 }
 
 /**
-- 
2.33.0