From 1d6448567122a53530f8cc588f34787db11c707e Mon Sep 17 00:00:00 2001
From: Zi Zhou <zi.zhou@bigswitch.com>
Date: Tue, 17 Apr 2018 22:29:59 -0700
Subject: [PATCH] Retry fan speed read when we see zero RPM, to make sure it's
 not a glitch

---
 .../builds/x86-64-accton-as6812-32x-fan.c     | 25 +++++++++++++------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/packages/platforms/accton/x86-64/x86-64-accton-as6812-32x/modules/builds/x86-64-accton-as6812-32x-fan.c b/packages/platforms/accton/x86-64/x86-64-accton-as6812-32x/modules/builds/x86-64-accton-as6812-32x-fan.c
index f0555674..43d3fe32 100644
--- a/packages/platforms/accton/x86-64/x86-64-accton-as6812-32x/modules/builds/x86-64-accton-as6812-32x-fan.c
+++ b/packages/platforms/accton/x86-64/x86-64-accton-as6812-32x/modules/builds/x86-64-accton-as6812-32x-fan.c
@@ -32,6 +32,7 @@
 #include <linux/kthread.h>
 #include <linux/device.h>
 #include <linux/platform_device.h>
+#include <linux/delay.h>
 
 #define FAN_MAX_NUMBER                   5
 #define FAN_SPEED_CPLD_TO_RPM_STEP       150
@@ -268,7 +269,7 @@ static int accton_as6812_32x_fan_write_value(u8 reg, u8 value)
 static void accton_as6812_32x_fan_update_device(struct device *dev)
 {
     int speed, r_speed, fault, r_fault, direction, ctrl_speed;
-    int i;
+    int i, retry_count;
     
     mutex_lock(&fan_data->update_lock);
 
@@ -298,6 +299,7 @@ static void accton_as6812_32x_fan_update_device(struct device *dev)
 
     for (i = 0; i < FAN_MAX_NUMBER; i++)
     {
+        retry_count = 5;
         /* Update fan data
          */
 
@@ -314,12 +316,21 @@ static void accton_as6812_32x_fan_update_device(struct device *dev)
         
         /* fan speed 
          */
-        speed   = accton_as6812_32x_fan_read_value(fan_speed_reg[i]);
-        r_speed = accton_as6812_32x_fan_read_value(fanr_speed_reg[i]);
-        if ( (speed < 0) || (r_speed < 0) )
-        {      
-            DEBUG_PRINT("[Error!!][%s][%d] \n", __FUNCTION__, __LINE__);      
-            goto _exit; /* error */ 
+        while (retry_count) {
+            retry_count--;
+            speed   = accton_as6812_32x_fan_read_value(fan_speed_reg[i]);
+            r_speed = accton_as6812_32x_fan_read_value(fanr_speed_reg[i]);
+            if ( (speed < 0) || (r_speed < 0) )
+            {
+                DEBUG_PRINT("[Error!!][%s][%d] \n", __FUNCTION__, __LINE__);
+                goto _exit; /* error */
+            }
+            if ( (speed == 0) || (r_speed == 0) )
+            {
+                msleep(200);
+                continue;
+            }
+            break;
         }
 
         DEBUG_PRINT("[fan%d:] speed:%d, r_speed=%d \n", i, speed, r_speed);