linux-kernel - [PATCH] ACPI: CPPC: Fix missing PCC check for guaranteed

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Message-ID: <20251210132227.1988380-1-zhangpengjie2@huawei.com>
Date: Wed, 10 Dec 2025 21:22:27 +0800
From: Pengjie Zhang <zhangpengjie2@...wei.com>
To: <rafael@...nel.org>, <lenb@...nel.org>,
	<srinivas.pandruvada@...ux.intel.com>
CC: <linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<zhanjie9@...ilicon.com>, <zhenglifeng1@...wei.com>, <lihuisong@...wei.com>,
	<yubowen8@...wei.com>, <linhongye@...artners.com>, <linuxarm@...wei.com>,
	<jonathan.cameron@...wei.com>, <zhangpengjie2@...wei.com>,
	<wangzhi12@...wei.com>
Subject: [PATCH] ACPI: CPPC: Fix missing PCC check for guaranteed

the current implementation overlooks the 'guaranteed_perf'
register in this check.

If the Guaranteed Performance register is located in the PCC
subspace, the function currently attempts to read it without
acquiring the lock and without sending the CMD_READ doorbell
to the firmware. This can result in reading stale data.

Fixes: 29523f095397 ("ACPI / CPPC: Add support for guaranteed performance")
Signed-off-by: Pengjie Zhang <zhangpengjie2@...wei.com>
---
 drivers/acpi/cppc_acpi.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 3bdeeee3414e..e66e20d1f31b 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -1366,7 +1366,8 @@ int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps)
 	/* 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(low_freq_reg) || CPC_IN_PCC(nom_freq_reg)) {
+		CPC_IN_PCC(low_freq_reg) || CPC_IN_PCC(nom_freq_reg) ||
+		CPC_IN_PCC(guaranteed_reg)) {
 		if (pcc_ss_id < 0) {
 			pr_debug("Invalid pcc_ss_id\n");
 			return -ENODEV;
-- 
2.33.0