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

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Message-ID: <alpine.DEB.2.02.1406112354070.23724@chino.kir.corp.google.com>
Date:	Wed, 11 Jun 2014 23:55:49 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Lan Tianyu <tianyu.lan@...el.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 Thu, 12 Jun 2014, Lan Tianyu wrote:

> Some machines'(E,G Lenovo Z480) ECs are not stable during boot up
> and causes battery driver fails to be probed due to failure of getting
> battery information from EC sometimes. After several retries, the
> operation will work. This patch is to retry to get battery information 5
> times if the first try fails.
> 
> Reported-and-tested-by: naszar <naszar@...ru>
> Reference: https://bugzilla.kernel.org/show_bug.cgi?id=75581
> Cc: stable@...r.kernel.org
> Signed-off-by: Lan Tianyu <tianyu.lan@...el.com>
> ---
>  drivers/acpi/battery.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
> index e48fc98..485009d 100644
> --- a/drivers/acpi/battery.c
> +++ b/drivers/acpi/battery.c
> @@ -34,6 +34,7 @@
>  #include <linux/dmi.h>
>  #include <linux/slab.h>
>  #include <linux/suspend.h>
> +#include <linux/delay.h>
>  #include <asm/unaligned.h>
>  
>  #ifdef CONFIG_ACPI_PROCFS_POWER
> @@ -1119,7 +1120,7 @@ static struct dmi_system_id bat_dmi_table[] = {
>  
>  static int acpi_battery_add(struct acpi_device *device)
>  {
> -	int result = 0;
> +	int result = 0, retry = 5;
>  	struct acpi_battery *battery = NULL;
>  
>  	if (!device)
> @@ -1135,7 +1136,16 @@ static int acpi_battery_add(struct acpi_device *device)
>  	mutex_init(&battery->sysfs_lock);
>  	if (acpi_has_method(battery->device->handle, "_BIX"))
>  		set_bit(ACPI_BATTERY_XINFO_PRESENT, &battery->flags);
> +
> +retry_get_info:
>  	result = acpi_battery_update(battery, false);
> +
> +	if (result && retry) {
> +		msleep(20);

We're really going to wait up to 20 * 5 = 100ms for acpi_battery_update() 
to succeed?  How are these the numbers that are determined to be optimal 
for probing?

> +		retry--;
> +		goto retry_get_info;
> +	}

This most certainly could be rewritten as a for-loop and remove the ugly 
goto.

> +
>  	if (result)
>  		goto fail;
>  #ifdef CONFIG_ACPI_PROCFS_POWER
--
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