linux-kernel - [PATCH v2 3/3] hwmon: (dell-smm) Warn if SMM call took a very long time to execute

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Date:   Tue, 26 Apr 2022 23:31:54 +0200
From:   Armin Wolf <W_Armin@....de>
To:     pali@...nel.org
Cc:     jdelvare@...e.com, linux@...ck-us.net, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 3/3] hwmon: (dell-smm) Warn if SMM call took a very long time to execute

If a particular SMM call takes a very long time to execute,
the user might experience audio problems. Print a warning
if a particular SMM call took over 0.250 seconds to execute,
so the user can check whether or not possible audio problems
are caused by this driver.

Signed-off-by: Armin Wolf <W_Armin@....de>
---
 drivers/hwmon/dell-smm-hwmon.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
index f13902414615..071aa6f4e109 100644
--- a/drivers/hwmon/dell-smm-hwmon.c
+++ b/drivers/hwmon/dell-smm-hwmon.c
@@ -49,6 +49,9 @@
 #define I8K_SMM_GET_DELL_SIG1	0xfea3
 #define I8K_SMM_GET_DELL_SIG2	0xffa3

+/* in usecs */
+#define DELL_SMM_MAX_DURATION  250000
+
 #define I8K_FAN_MULT		30
 #define I8K_FAN_RPM_THRESHOLD	1000
 #define I8K_MAX_TEMP		127
@@ -239,6 +242,9 @@ static int i8k_smm_func(void *par)
 	pr_debug("smm(0x%.4x 0x%.4x) = 0x%.4x  (took %7lld usecs)\n", eax, ebx,
 		 (rc ? 0xffff : regs->eax & 0xffff), duration);

+	if (duration > DELL_SMM_MAX_DURATION)
+		pr_warn_once("SMM call took %lld usecs!\n", duration);
+
 	return rc;
 }

--
2.30.2