Re: [PATCH] power_supply: rt9455_charger: Properly notify userspace about charging events

[Krzysztof Kozlowski]

On 02.07.2015 16:40, Anda-Maria Nicolae wrote:
> Hello Krzysztof,
> 
> The information provided to userspace is not accurate in current driver
> implementation and it is accurate with this patch.
> Also, when the battery is reconnected to the charger (after it has been
> disconnected from the charger), the charger does not trigger any
> interrupt. Since power_supply_changed() is called only in interrupt
> handler, the userspace is never notified that the battery is reconnected.
> 
> Let me explain to you why power_supply_changed() is called in
> rt9455_pwr_rdy_work_callback() and not in interrupt handler, when CHRVPI
> interrupt occurs.
> 
> I created a userspace tool that waits for notifications from the driver.
> A notification is sent when the driver calls power_supply_changed().
> When my userspace tool receives a notification, it reads the files from
> /sys/class/power_supply/rt9455-charger/ folder. The tool reads each file
> this to figure it out what has been changed, since the driver notifies
> the tool only when a change has been made.
> These files include /sys/class/power_supply/rt9455-charger/online. This
> file displays 1 if the power source is connected to the charger and 0
> otherwise.
> When the userspace tool reads
> /sys/class/power_supply/rt9455-charger/online,
> rt9455_charger_get_online() function from the driver is called.
> rt9455_charger_get_online() returns the value of PWR_RDY bit.
> But whenever the power source is connected to / disconnected from the
> charger, RT9455 first sets CHRVPI interrupt bit, triggers an interrupt,
> and after almost 1-2 seconds, the charger also updates PWR_RDY bit.
> So, if we check PWR_RDY bit immediately after CHRVPI bit is set, we will
> not obtain accurate info about the change that has been made (i.e.: if
> the power source was connected or disconnected).
> This is why the driver has struct delayed_work pwr_rdy_work, which is
> scheduled whenever CHRVPI interrupt bit is set.
> This is why in this patch, in rt9455_pwr_rdy_work_callback(),
> power_supply_changed() is called, and not in interrupt handler.

That explains it, thank you. It would be nice if such answer to "why"
would be also in commit message (maybe a shorter one).

Beside of that the patch looks good:
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx>

Best regards,
Krzysztof



> 
> Let me explain to you why power_supply_changed() is called in
> rt9455_batt_presence_work_callback().
> 
> As previously stated, the userspace tool is never notified that the
> battery is reconnected. But since the driver uses struct delayed_work
> batt_presence_work, to determine whether the battery has been
> reconnected, we can call power_supply_changed() whenever the driver
> determines the battery is reconnected (i.e. BATAB interrupt bit is
> cleared).
> This is why in this patch, in rt9455_batt_presence_work_callback(),
> power_supply_changed() is called.
> 
> On 07/02/2015 03:49 AM, Krzysztof Kozlowski wrote:
>> 2015-06-18 1:28 GMT+09:00 Anda-Maria Nicolae
>> <anda-maria.nicolae@xxxxxxxxx>:
>>> Do not call power_supply_changed() when CHRVPI interrupt has occurred.
>> What I cannot find here is the answer to: why? I am not familiar with
>> the driver so this is just guessing that you wanted to notify
>> userspace about connected/disconnected charger. In both cases (before
>> and after the patch) this is achieved, isn't it?
>>
>> Best regards,
>> Krzysztof
>>
>>
>>> CHRVPI interrupt occurs when the charger is connected to or disconnected
>>> from the power source. Call power_supply_changed() after PWR_RDY bit is
>>> read, to distinguish between connection to or disconnection from the
>>> power
>>> source.
>>> Also, call power_supply_changed() after the battery is reconnected to
>>> the
>>> charger, to notify userspace that the battery is no longer absent.
>>>
>>> Signed-off-by: Anda-Maria Nicolae <anda-maria.nicolae@xxxxxxxxx>
>>> ---
>>>   drivers/power/rt9455_charger.c |   16 ++++++++++++++--
>>>   1 file changed, 14 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/power/rt9455_charger.c
>>> b/drivers/power/rt9455_charger.c
>>> index 08baac6..a49a9d4 100644
>>> --- a/drivers/power/rt9455_charger.c
>>> +++ b/drivers/power/rt9455_charger.c
>>> @@ -973,7 +973,6 @@ static int
>>> rt9455_irq_handler_check_irq2_register(struct rt9455_info *info,
>>>
>>>          if (irq2 & GET_MASK(F_CHRVPI)) {
>>>                  dev_dbg(dev, "Charger fault occurred\n");
>>> -               alert_userspace = true;
>>>                  /*
>>>                   * CHRVPI bit is set in 2 cases:
>>>                   * 1. when the power source is connected to the
>>> charger.
>>> @@ -981,6 +980,9 @@ static int
>>> rt9455_irq_handler_check_irq2_register(struct rt9455_info *info,
>>>                   * To identify the case, PWR_RDY bit is checked.
>>> Because
>>>                   * PWR_RDY bit is set / cleared after CHRVPI
>>> interrupt is
>>>                   * triggered, it is used delayed_work to later read
>>> PWR_RDY bit.
>>> +                * Also, do not set to true alert_userspace, because
>>> there is no
>>> +                * need to notify userspace when CHRVPI interrupt has
>>> occurred.
>>> +                * Userspace will be notified after PWR_RDY bit is read.
>>>                   */
>>>                  queue_delayed_work(system_power_efficient_wq,
>>>                                     &info->pwr_rdy_work,
>>> @@ -1178,7 +1180,7 @@ static irqreturn_t
>>> rt9455_irq_handler_thread(int irq, void *data)
>>>                  /*
>>>                   * Sometimes, an interrupt occurs while
>>> rt9455_probe() function
>>>                   * is executing and power_supply_register() is not
>>> yet called.
>>> -                * Do not call power_supply_charged() in this case.
>>> +                * Do not call power_supply_changed() in this case.
>>>                   */
>>>                  if (info->charger)
>>>                          power_supply_changed(info->charger);
>>> @@ -1478,6 +1480,11 @@ static void
>>> rt9455_pwr_rdy_work_callback(struct work_struct *work)
>>>                                     RT9455_MAX_CHARGING_TIME * HZ);
>>>                  break;
>>>          }
>>> +       /*
>>> +        * Notify userspace that the charger has been either
>>> connected to or
>>> +        * disconnected from the power source.
>>> +        */
>>> +       power_supply_changed(info->charger);
>>>   }
>>>
>>>   static void rt9455_max_charging_time_work_callback(struct
>>> work_struct *work)
>>> @@ -1533,6 +1540,11 @@ static void
>>> rt9455_batt_presence_work_callback(struct work_struct *work)
>>>                          if (ret)
>>>                                  dev_err(dev, "Failed to unmask BATAB
>>> interrupt\n");
>>>                  }
>>> +               /*
>>> +                * Notify userspace that the battery is now connected
>>> to the
>>> +                * charger.
>>> +                */
>>> +               power_supply_changed(info->charger);
>>>          }
>>>   }
>>>
>>> -- 
>>> 1.7.9.5
>>>
>>> -- 
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> 
> 

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