linux-kernel - RE: [PATCH] usb: cdns3: platform_get_irq_byname_optional instead platform_get_irq

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Date:   Mon, 5 Oct 2020 05:54:02 +0000
From:   Pawel Laszczak <pawell@...ence.com>
To:     Roger Quadros <rogerq@...com>,
        "balbi@...nel.org" <balbi@...nel.org>
CC:     "peter.chen@....org" <peter.chen@....org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Rahul Kumar <kurahul@...ence.com>
Subject: RE: [PATCH] usb: cdns3: platform_get_irq_byname_optional instead
 platform_get_irq_byname

Roger,
>
>Pawel,
>
>On 02/10/2020 12:08, Pawel Laszczak wrote:
>> Roger,
>>
>>>
>>> On 30/09/2020 09:57, Pawel Laszczak wrote:
>>>> To avoid duplicate error information patch replaces platform_get_irq_byname
>>>> into platform_get_irq_byname_optional.
>>>
>>> What is duplicate error information?
>>
>> The function platform_get_irq_byname print:
>> " dev_err(&dev->dev, "IRQ %s not found\n", name);" if error occurred.
>>
>> In core.c we have the another error message below invoking this function.
>> e.g
>> 	if (cdns->dev_irq < 0)
>> 		dev_err(dev, "couldn't get peripheral irq\n");
>>
>> So, it's looks like one dev_err is  redundant.
>
>If we want all 3 IRQs to be valid irrespective of dr_mode then we should
>use platform_get_irq_byname() and error out in probe if (ret < 0 && ret != -EPROBE_DEFER).
>
>We can get rid of the irq check and duplicate error message in other places.

To be sure we understand each other correctly.

Are You suggesting  to leave the  platform_get_irq_byname()
and rid of from core.c the following lines :

if (cdns->dev_irq < 0)
	dev_err(dev, "couldn't get peripheral irq\n");
	
and

dev_err(dev, "couldn't get otg irq\n"); 
?

A word of explanation why this patch has been sent.
During reviewing the cdnsp driver Chunfeng Yun add such comment:

"
> +	cdns->dev_irq = platform_get_irq_byname(pdev, "peripheral");
> +	if (cdns->dev_irq == -EPROBE_DEFER)
> +		return cdns->dev_irq;
> +
> +	if (cdns->dev_irq < 0)
> +		dev_err(dev, "couldn't get peripheral irq\n");
Use platform_get_irq_byname_optional? otherwise no need print this log,
platform_get_irq_byname() will print it. 
"

In this patch I've chosen the platform_get_irq_byname_optional because both
function do the same but the error message from core.c tell us little more then
generic message from platform_get_irq_byname.

Cheers
Pawel Laszczak

>
>cheers,
>-roger
>
>>
>>>
>>>>
>>>> A change was suggested during reviewing CDNSP driver by Chunfeng Yun.
>>>>
>>>> Signed-off-by: Pawel Laszczak <pawell@...ence.com>
>>>> ---
>>>>    drivers/usb/cdns3/core.c | 4 ++--
>>>>    1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/usb/cdns3/core.c b/drivers/usb/cdns3/core.c
>>>> index a0f73d4711ae..a3f6dc44cf3a 100644
>>>> --- a/drivers/usb/cdns3/core.c
>>>> +++ b/drivers/usb/cdns3/core.c
>>>> @@ -465,7 +465,7 @@ static int cdns3_probe(struct platform_device *pdev)
>>>>
>>>>    	cdns->xhci_res[1] = *res;
>>>>
>>>> -	cdns->dev_irq = platform_get_irq_byname(pdev, "peripheral");
>>>> +	cdns->dev_irq = platform_get_irq_byname_optional(pdev, "peripheral");
>>>
>>> As per DT binding document, these are mandatory properties
>>
>> I think that name platform_get_irq_byname_optional is little confusing.
>> Function descriptions show that both are almost identical:
>> /**
>>   * platform_get_irq_byname_optional - get an optional IRQ for a device by name
>>   * @dev: platform device
>>   * @name: IRQ name
>>   *
>>   * Get an optional IRQ by name like platform_get_irq_byname(). Except that it
>>   * does not print an error message if an IRQ can not be obtained.
>>   *
>>   * Return: non-zero IRQ number on success, negative error number on failure.
>>   */
>>
>>>
>>>   - interrupts: Interrupts used by cdns3 controller:
>>>          "host" - interrupt used by XHCI driver.
>>>          "peripheral" - interrupt used by device driver
>>>          "otg" - interrupt used by DRD/OTG  part of driver
>>>
>>> for dr_mode == "otg" -> all 3 are mandatory.
>>> for dr_mode == "host" -> "otg" and "peripheral" IRQs are not required.
>>> for dr_mode == "periphearal" -> "otg" and "host" IRQs are not required.
>>>
>>>>    	if (cdns->dev_irq == -EPROBE_DEFER)
>>>>    		return cdns->dev_irq;
>>>>
>>>> @@ -477,7 +477,7 @@ static int cdns3_probe(struct platform_device *pdev)
>>>>    		return PTR_ERR(regs);
>>>>    	cdns->dev_regs	= regs;
>>>>
>>>> -	cdns->otg_irq = platform_get_irq_byname(pdev, "otg");
>>>> +	cdns->otg_irq = platform_get_irq_byname_optional(pdev, "otg");
>>>>    	if (cdns->otg_irq == -EPROBE_DEFER)
>>>>    		return cdns->otg_irq;
>>>>
>>>>
>>>
>>
>> Regards,
>> Pawel
>>
>
>--
>Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
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