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@xxxxx> >>>> Reference: https://bugzilla.kernel.org/show_bug.cgi?id=75581 >>>> Cc: stable@xxxxxxxxxxxxxxx >>>> Signed-off-by: Lan Tianyu <tianyu.lan@xxxxxxxxx> >>>> --- >>>> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
