linux-kernel - [PATCH 2/2] acpi: CPPC: read delivered_reg and reference

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Message-ID: <20230515100005.3540793-2-zengheng4@huawei.com>
Date:   Mon, 15 May 2023 18:00:04 +0800
From:   Zeng Heng <zengheng4@...wei.com>
To:     <lenb@...nel.org>, <viresh.kumar@...aro.org>, <rafael@...nel.org>
CC:     <weiyongjun1@...wei.com>, <linux-pm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <xiexiuqi@...wei.com>,
        <linux-acpi@...r.kernel.org>, <liwei391@...wei.com>,
        <wangxiongfeng2@...wei.com>
Subject: [PATCH 2/2] acpi: CPPC: read delivered_reg and reference_reg in critical section

Reading the content of delivered_reg and reference_reg should be in
the same critical section, in case any interrupt comes, which could
lead to inaccurate frequency calculation.

Signed-off-by: Zeng Heng <zengheng4@...wei.com>
---
 drivers/acpi/cppc_acpi.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index c51d3ccb4cca..176f3e2e67f8 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -1315,6 +1315,7 @@ int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs)
 	struct cppc_pcc_data *pcc_ss_data = NULL;
 	u64 delivered, reference, ref_perf, ctr_wrap_time;
 	int ret = 0, regs_in_pcc = 0;
+	unsigned long flags;
 
 	if (!cpc_desc) {
 		pr_debug("No CPC descriptor for CPU:%d\n", cpunum);
@@ -1350,8 +1351,11 @@ int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs)
 		}
 	}
 
+	local_irq_save(flags);
 	cpc_read(cpunum, delivered_reg, &delivered);
 	cpc_read(cpunum, reference_reg, &reference);
+	local_irq_restore(flags);
+
 	cpc_read(cpunum, ref_perf_reg, &ref_perf);
 
 	/*
-- 
2.25.1