linux-kernel - [PATCH AUTOSEL 4.19 074/192] cpufreq: acpi-cpufreq: Report if CPU doesn't support boost technologies

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Date:   Wed, 27 Mar 2019 14:08:26 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Erwan Velu <erwanaliasr1@...il.com>,
        Erwan Velu <e.velu@...teo.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Sasha Levin <sashal@...nel.org>, linux-pm@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 074/192] cpufreq: acpi-cpufreq: Report if CPU doesn't support boost technologies

From: Erwan Velu <erwanaliasr1@...il.com>

[ Upstream commit 1222d527f314c86a3b59a522115d62facc5a7965 ]

There is some rare cases where CPB (and possibly IDA) are missing on
processors.

This is the case fixed by commit f7f3dc00f612 ("x86/cpu/AMD: Fix
erratum 1076 (CPB bit)") and following.

In such context, the boost status isn't reported by
/sys/devices/system/cpu/cpufreq/boost.

This commit is about printing a message to report that the CPU
doesn't expose the boost capabilities.

This message could help debugging platforms hit by this phenomena.

Signed-off-by: Erwan Velu <e.velu@...teo.com>
[ rjw: Change the message text somewhat ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/cpufreq/acpi-cpufreq.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
index b61f4ec43e06..aca30f45172e 100644
--- a/drivers/cpufreq/acpi-cpufreq.c
+++ b/drivers/cpufreq/acpi-cpufreq.c
@@ -911,8 +911,10 @@ static void __init acpi_cpufreq_boost_init(void)
 {
 	int ret;
 
-	if (!(boot_cpu_has(X86_FEATURE_CPB) || boot_cpu_has(X86_FEATURE_IDA)))
+	if (!(boot_cpu_has(X86_FEATURE_CPB) || boot_cpu_has(X86_FEATURE_IDA))) {
+		pr_debug("Boost capabilities not present in the processor\n");
 		return;
+	}
 
 	acpi_cpufreq_driver.set_boost = set_boost;
 	acpi_cpufreq_driver.boost_enabled = boost_state(0);
-- 
2.19.1