Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH] extcon: palmas: hide error messages if gpio returns
 -EPROBE_DEFER
To:     "H. Nikolaus Schaller" <hns@goldelico.com>
Cc:     MyungJoo Ham <myungjoo.ham@samsung.com>,
        linux-kernel@vger.kernel.org, letux-kernel@openphoenux.org,
        kernel@pyra-handheld.com, linux-omap@vger.kernel.org
From:   Chanwoo Choi <cw00.choi@samsung.com>
Organization: Samsung Electronics
Message-ID: <36bac0ac-f772-9f04-fb64-1c11e9d86fa5@samsung.com>
Date:   Mon, 17 Feb 2020 20:24:04 +0900
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:59.0) Gecko/20100101
        Thunderbird/59.0
MIME-Version: 1.0
In-Reply-To: <2DF972B9-EECF-44E9-93FC-74B6C3B6FFC2@goldelico.com>
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Content-Type: text/plain; charset="utf-8"
CMS-TYPE: 101P
DLP-Filter: Pass
References: <CGME20200217085551epcas1p49113220d034155f8a78dc5e0767637a5@epcas1p4.samsung.com>
        <f65ad0ef2866e7d5b6743e13579c1efe8c572b4f.1581929741.git.hns@goldelico.com>
        <b9fe52e9-0340-4204-ee85-44b6c1ea7f3b@samsung.com>
        <2DF972B9-EECF-44E9-93FC-74B6C3B6FFC2@goldelico.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi,

On 2/17/20 8:07 PM, H. Nikolaus Schaller wrote:
> Hi Chanwoo Choi,
> 
>> Am 17.02.2020 um 11:15 schrieb Chanwoo Choi <cw00.choi@samsung.com>:
>>
>> Hi,
>>
>> On 2/17/20 5:55 PM, H. Nikolaus Schaller wrote:
>>> If the gpios are probed after this driver (e.g. if they
>>> come from an i2c expander) there is no need to print an
>>> error message.
>>>
>>> Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
>>> ---
>>> drivers/extcon/extcon-palmas.c | 6 ++++--
>>> 1 file changed, 4 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/extcon/extcon-palmas.c b/drivers/extcon/extcon-palmas.c
>>> index edc5016f46f1..9c6254c0531c 100644
>>> --- a/drivers/extcon/extcon-palmas.c
>>> +++ b/drivers/extcon/extcon-palmas.c
>>> @@ -206,14 +206,16 @@ static int palmas_usb_probe(struct platform_device *pdev)
>>> 	palmas_usb->id_gpiod = devm_gpiod_get_optional(&pdev->dev, "id",
>>> 							GPIOD_IN);
>>> 	if (IS_ERR(palmas_usb->id_gpiod)) {
>>> -		dev_err(&pdev->dev, "failed to get id gpio\n");
>>> +		if (PTR_ERR(palmas_usb->id_gpiod) != -EPROBE_DEFER)
>>> +			dev_err(&pdev->dev, "failed to get id gpio\n");
>>> 		return PTR_ERR(palmas_usb->id_gpiod);
>>> 	}


How about editing it ? as following:
because following suggestion reduces the one checking behavior
when return value is -EPROBE_DEFER.

	if (PTR_ERR(palmas_usb->id_gpiod) == -EPROBE_DEFER) {
		return -EPROBE_DEFER;
	} else if (IS_ERR(palmas_usb->id_gpiod)) {
		dev_err(&pdev->dev, "failed to get id gpio\n");
		return PTR_ERR(palmas_usb->id_gpiod);
	}

>>>
>>> 	palmas_usb->vbus_gpiod = devm_gpiod_get_optional(&pdev->dev, "vbus",
>>> 							GPIOD_IN);
>>> 	if (IS_ERR(palmas_usb->vbus_gpiod)) {
>>> -		dev_err(&pdev->dev, "failed to get vbus gpio\n");
>>> +		if (PTR_ERR(palmas_usb->vbus_gpiod) != -EPROBE_DEFER)
>>> +			dev_err(&pdev->dev, "failed to get vbus gpio\n");

ditto.

>>> 		return PTR_ERR(palmas_usb->vbus_gpiod);
>>> 	}
>>>
>>>
>>
>> Usually, gpio driver like pinctrl is very early probed
>> because almost device drivers should use gpio.
>> So, I have not any experience about this situation.
>> Do you meet this situation on any h/w board?
> 
> Yes, I have experienced that sometimes on omap5+palmas based boards.
> 
> It seems to be this:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/omap5-board-common.dtsi?h=v5.6-rc2#n384
> 
> The extcon_usb3 can potentially match this extcon-palmas driver at
> a moment where the palmas_gpio it is referring to has not yet been
> successfully probed. Then the palmas_gpio would return -EPROBE_DEFER.
> 
> AFAIK there is no guarantee for a specific sequence of drivers
> being probed and it is pure luck that in most cases the gpios
> are already probed.

Thanks for explaining the example.


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics