Date:   Wed, 03 Jan 2018 09:58:41 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Hans de Goede <hdegoede@...hat.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] extcon: axp288: Redo charger type dection a couple
 of seconds after probe()

Hi Hans,

On 2018년 01월 03일 07:44, Hans de Goede wrote:
> Hi,
> 
> On 02-01-18 01:54, Chanwoo Choi wrote:
>> Hi Hans,
>>
>> s/dection/detection on patch title.
> 
> Thank you for all the reviews.
> 
> I've fixed the typo in my personal tree.
> 
>> On 2017년 12월 22일 21:36, Hans de Goede wrote:
>>> The axp288 extcon code depends on other drivers to do things like mux the
>>> data lines, enable/disable vbus based on the id-pin, etc.
>>>
>>> Sometimes the BIOS has not set these things up correctly resulting in the
>>> initial charger cable type detection giving a wrong result and we end up
>>> not charging or charging at only 0.5A.
>>>
>>> This commit starts a second charger-detection cycle a couple of seconds
>>> after the first one finishes, giving the other drivers time to load and
>>> do their thing.
>>>
>>> Signed-off-by: Hans de Goede <hdegoede@...hat.com>
>>> ---
>>>   drivers/extcon/extcon-axp288.c | 32 ++++++++++++++++++++++++++++++--
>>>   1 file changed, 30 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/extcon/extcon-axp288.c b/drivers/extcon/extcon-axp288.c
>>> index 386afb7d1160..cc7c35c7ff02 100644
>>> --- a/drivers/extcon/extcon-axp288.c
>>> +++ b/drivers/extcon/extcon-axp288.c
>>> @@ -1,6 +1,7 @@
>>>   /*
>>>    * extcon-axp288.c - X-Power AXP288 PMIC extcon cable detection driver
>>>    *
>>> + * Copyright (C) 2016-2017 Hans de Goede <hdegoede@...hat.com>
>>>    * Copyright (C) 2015 Intel Corporation
>>>    * Author: Ramakrishna Pallala <ramakrishna.pallala@...el.com>
>>>    *
>>> @@ -97,9 +98,11 @@ struct axp288_extcon_info {
>>>       struct device *dev;
>>>       struct regmap *regmap;
>>>       struct regmap_irq_chip_data *regmap_irqc;
>>> +    struct delayed_work det_work;
>>>       int irq[EXTCON_IRQ_END];
>>>       struct extcon_dev *edev;
>>>       unsigned int previous_cable;
>>> +    bool first_detect_done;
>>
>> The first_detect_done is used only one time in the axp288_handle_chrg_det_event().
>> The other function don't use it. So, you better to define and use
>> 'static bool first_detect_done' in the axp288_handle_chrg_det_event()
>> instead of defining the 'first_detect_done' in the struct axp288_extcon_info.
> 
> But what if a device has 2 axp288 PMICs (unlikely I know) then only the
> first one to check this will do the re-detect 2 seconds later, unless they
> race, which is bad in itself too.
> 
> In general using static function variables is a bad idea and should be
> avoided, it does not work when their are multiple instances of the device
> and it is racy. So sorry but I'm not going to make this change.

You're right. It is my mistake. Please keep your way.

> 
>>
>>>   };
>>>     /* Power up/down reason string array */
>>> @@ -137,6 +140,25 @@ static void axp288_extcon_log_rsi(struct axp288_extcon_info *info)
>>>       regmap_write(info->regmap, AXP288_PS_BOOT_REASON_REG, clear_mask);
>>>   }
>>>   +static void axp288_chrg_detect_complete(struct axp288_extcon_info *info)
>>> +{
>>> +    /*
>>> +     * We depend on other drivers to do things like mux the data lines,
>>> +     * enable/disable vbus based on the id-pin, etc. Sometimes the BIOS has
>>> +     * not set these things up correctly resulting in the initial charger
>>> +     * cable type detection giving a wrong result and we end up not charging
>>> +     * or charging at only 0.5A.
>>> +     *
>>> +     * So we schedule a second cable type detection after 2 seconds to
>>> +     * give the other drivers time to load and do their thing.
>>> +     */
>>> +    if (!info->first_detect_done) {
>>> +        queue_delayed_work(system_wq, &info->det_work,
>>> +                   msecs_to_jiffies(2000));
>>> +        info->first_detect_done = true;
>>> +    }
>>> +}
>>
>> The axp288_chrg_detect_complete() is only used in the axp288_handle_chrg_det_event()
>> and axp288_chrg_detect_complete() is not a complicate. I think that you don't need
>> to make the separate function. I'd like you to add the
>>
>>> +
>>>   static int axp288_handle_chrg_det_event(struct axp288_extcon_info *info)
>>>   {
>>>       int ret, stat, cfg, pwr_stat;
>>> @@ -201,6 +223,8 @@ static int axp288_handle_chrg_det_event(struct axp288_extcon_info *info)
>>>           info->previous_cable = cable;
>>>       }
>>>   +    axp288_chrg_detect_complete(info);
>>
>> As I commented, you better to add the code directly instead of separate function.
> 
> I would prefer to keep this as a separate function, that keeps the main
> flow of the axp288_handle_chrg_det_event function a lot more readable IMHO.
> 
> axp288_handle_chrg_det_event already has a non trivial code flow adding more
> conditional code to it only makes it harder to read.
> 
> But if you insist I can move the code inside the function for v2. Note that
> this will not make a difference for the code generated by the compiler, the
> compiler will auto-inline it anyways.

I didn't mention the result from compiler. I focus on the readability.
On v1, the developer always check what to do in axp288_chrg_detect_complete()
even if this function is used only one time like '__init'.
Actually, axp288_chrg_detect_complete() is not complicate and short.

But, I will not be forced because it is not a critical issue.
If you want to keep the separate function, you just send v2 with only fixing the typo.

> 
> 
>>
>>> +
>>>       return 0;
>>>     dev_det_ret:
>>> @@ -222,8 +246,11 @@ static irqreturn_t axp288_extcon_isr(int irq, void *data)
>>>       return IRQ_HANDLED;
>>>   }
>>>   -static void axp288_extcon_enable(struct axp288_extcon_info *info)
>>> +static void axp288_extcon_det_work(struct work_struct *work)
>>>   {
>>> +    struct axp288_extcon_info *info =
>>> +        container_of(work, struct axp288_extcon_info, det_work.work);
>>> +
>>>       regmap_update_bits(info->regmap, AXP288_BC_GLOBAL_REG,
>>>                           BC_GLOBAL_RUN, 0);
>>>       /* Enable the charger detection logic */
>>> @@ -245,6 +272,7 @@ static int axp288_extcon_probe(struct platform_device *pdev)
>>>       info->regmap = axp20x->regmap;
>>>       info->regmap_irqc = axp20x->regmap_irqc;
>>>       info->previous_cable = EXTCON_NONE;
>>> +    INIT_DELAYED_WORK(&info->det_work, axp288_extcon_det_work);
>>>         platform_set_drvdata(pdev, info);
>>>   @@ -287,7 +315,7 @@ static int axp288_extcon_probe(struct platform_device *pdev)
>>>       }
>>>         /* Start charger cable type detection */
>>> -    axp288_extcon_enable(info);
>>> +    queue_delayed_work(system_wq, &info->det_work, 0);
>>>         return 0;
>>>   }
>>>
>>
>>
> 
> Regards,
> 
> Hans
> 
> 
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics

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