[PATCH 6/6] hwmon: (dell-smm) In debug mode log duration of SMM calls

[Pali Rohár]

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.ro...@gmail.com>
---
 drivers/hwmon/dell-smm-hwmon.c |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
index 571d498..acf9c03 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;
 }
 
-- 
1.7.9.5