hwmon: (dell-smm) In debug mode log duration of SMM calls

This allow us to debug how long take each SMM call and how long is system
frozen in SMM handler.

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

1 files changed, 17 insertions, 0 deletions

diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
index 571d4984d39c..acf9c0361d9f 100644
--- a/drivers/hwmon/dell-smm-hwmon.c
+++ b/drivers/hwmon/dell-smm-hwmon.c
@@ -140,6 +140,14 @@ static int i8k_smm(struct smm_regs *regs)
         int eax = regs->eax;
         cpumask_var_t old_mask;
 
+#ifdef DEBUG
+        int ebx = regs->ebx;
+        unsigned long duration;
+        ktime_t calltime, delta, rettime;
+
+        calltime = ktime_get();
+#endif
+
         /* SMM requires CPU 0 */
         if (!alloc_cpumask_var(&old_mask, GFP_KERNEL))
                 return -ENOMEM;
@@ -211,6 +219,15 @@ static int i8k_smm(struct smm_regs *regs)
 out:
         set_cpus_allowed_ptr(current, old_mask);
         free_cpumask_var(old_mask);
+
+#ifdef DEBUG
+        rettime = ktime_get();
+        delta = ktime_sub(rettime, calltime);
+        duration = ktime_to_ns(delta) >> 10;
+        pr_debug("smm(0x%.4x 0x%.4x) = 0x%.4x  (took %7lu usecs)\n", eax, ebx,
+                (rc ? 0xffff : regs->eax & 0xffff), duration);
+#endif
+
         return rc;
 }