[PATCH v7 2/8] ACPI: CPPC: Optimize cppc_get_perf()

[Lifeng Zheng]

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 ensure the pointer 'perf' is no null.

3. Add a check to verify if the register is supported to be read before
using it. The logic is:

(1) If the register is of the integer type, check whether the register is
optional and its value is 0. If yes, the register is not supported.

(2) If the register is of other types, a null one is not supported.

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

Reviewed-by: Pierre Gondois <pierre.gondois@xxxxxxx>
Signed-off-by: Lifeng Zheng <zhenglifeng1@xxxxxxxxxx>
---
 drivers/acpi/cppc_acpi.c | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 39f019e265da..4965a6465538 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -1194,6 +1194,9 @@ static int cppc_get_perf(int cpunum, enum cppc_regs reg_idx, u64 *perf)
 	struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpunum);
 	struct cpc_register_resource *reg;
 
+	if (perf == NULL)
+		return -EINVAL;
+
 	if (!cpc_desc) {
 		pr_debug("No CPC descriptor for CPU:%d\n", cpunum);
 		return -ENODEV;
@@ -1201,20 +1204,29 @@ static int cppc_get_perf(int cpunum, enum cppc_regs reg_idx, u64 *perf)
 
 	reg = &cpc_desc->cpc_regs[reg_idx];
 
+	if ((reg->type == ACPI_TYPE_INTEGER && IS_OPTIONAL_CPC_REG(reg_idx) &&
+	     !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 (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 +1235,7 @@ 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