linux-kernel - Re: [PATCH] ACPI/Battery: Retry to get Battery information if failed during probing

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Date:	Fri, 13 Jun 2014 10:25:00 +0800
From:	Lan Tianyu <tianyu.lan@...el.com>
To:	David Rientjes <rientjes@...gle.com>
CC:	rjw@...ysocki.net, lenb@...nel.org, naszar@...ru,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] ACPI/Battery: Retry to get Battery information if failed
 during probing

On 2014年06月13日 05:17, David Rientjes wrote:
> On Thu, 12 Jun 2014, Lan Tianyu wrote:
> 
>> The retry time is set by randomly and not accurate because don't know
>> when EC will work normally. Set the retry time to 5 just in order to
>> make sure battery driver probing sucessfully every time,
>>
> 
> Ok, I was hoping to avoid the excessive wait if it will never actually 
> succeed

Ok. The battery driver has used async init and so this will not affect
the speed of boot up.

> but I assume there's some evidence that it can succeed after 40ms, 
> 60ms, etc.  Please consider the following instead:
> 
> 	for (i = 0; i < 5; i++) {
> 		/* Comment on why we need a delay in between retries */
> 		if (i)
> 			msleep(20);
> 		result = acpi_battery_update(battery, false);
> 		if (!result)
> 			break;
> 	}
> 

How about this?

-       result = acpi_battery_update(battery, false);
-       if (result)
+
+       /*
+        * Some machines'(E,G Lenovo Z480) ECs are not stable
+        * during boot up and this causes battery driver fails to be
+        * probed due to failure of getting battery information
+        * from EC sometimes. After several retries, the operation
+        * may work. So add retry code here and 20ms sleep between
+        * every retries.
+        */
+       while (acpi_battery_update(battery, false) && retry--)
+               msleep(20);
+       if (!retry) {
+               result = -ENODEV;
                goto fail;
+       }
+




-- 
Best regards
Tianyu Lan
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