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SubjectRe: [PATCH] ACPI/Battery: Retry to get Battery information if failed during probing
On 2014年06月12日 15:26, David Rientjes wrote:
> 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@ya.ru>
>>>> Reference: https://bugzilla.kernel.org/show_bug.cgi?id=75581
>>>> Cc: stable@vger.kernel.org
>>>> Signed-off-by: Lan Tianyu <tianyu.lan@intel.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);
>>>
>>
>> Hi David:
>> Thanks for review.
>>
>>> We're really going to wait up to 20 * 5 = 100ms for acpi_battery_update()
>>> to succeed?
>>
>> No, this depends which retry acpi_battery_update() will succeed. For
>> most machines, there will be no delay.
>>
>
> Right, but you're willing to wait up to 100ms for it to succeed? You're
> implementing x retries with y ms sleep in between, I'm asking how it is
> determined that the optimal values are x = 5 and y = 20. More directly:
> is it possible to succeed at 101ms?

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,

> Is it really likely to succeed after
> the first 20ms?
>

Yes, it's possible.
From naszar's test log, acpi_battery_update() failed only once. But not
sure that this happens every time, treat it conservatively and set the
retry time to 5.
https://bugzilla.kernel.org/attachment.cgi?id=139081&action=edit

--
Best regards
Tianyu Lan
--
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