Commit 6ea3a44c authored by Pengjie Zhang's avatar Pengjie Zhang Committed by Rafael J. Wysocki
Browse files

ACPI: CPPC: Fix missing PCC check for guaranteed_perf 



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: 29523f09 ("ACPI / CPPC: Add support for guaranteed performance")
Signed-off-by: default avatarPengjie Zhang <zhangpengjie2@huawei.com>
Cc: 4.20+ <stable@vger.kernel.org> # 4.20+
[ rjw: Subject and changelog edits ]
Link: https://patch.msgid.link/20251210132227.1988380-1-zhangpengjie2@huawei.com


Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 8f0b4cce

drivers/acpi/cppc_acpi.c

+2 −1
Original line number Diff line number Diff line
@@ -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;