linux-kernel - RE: [PATCH v1 2/2] usb:cdns3 Add Cadence USB3 DRD Driver

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Date:   Mon, 17 Dec 2018 13:56:27 +0200
From:   Felipe Balbi <balbi@...nel.org>
To:     Pawel Laszczak <pawell@...ence.com>,
        "devicetree\@vger.kernel.org" <devicetree@...r.kernel.org>,
        Kishon Vijay Abraham I <kishon@...com>
Cc:     "gregkh\@linuxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-usb\@vger.kernel.org" <linux-usb@...r.kernel.org>,
        "rogerq\@ti.com" <rogerq@...com>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        Alan Douglas <adouglas@...ence.com>,
        "jbergsagel\@ti.com" <jbergsagel@...com>,
        "nsekhar\@ti.com" <nsekhar@...com>, "nm\@ti.com" <nm@...com>,
        Suresh Punnoose <sureshp@...ence.com>,
        "peter.chen\@nxp.com" <peter.chen@....com>,
        Pawel Jez <pjez@...ence.com>, Rahul Kumar <kurahul@...ence.com>
Subject: RE: [PATCH v1 2/2] usb:cdns3 Add Cadence USB3 DRD Driver


Hi,

Pawel Laszczak <pawell@...ence.com> writes:
>>>>> +static irqreturn_t cdns3_device_irq_handler(int irq, void *data)
>>>>> +{
>>>>> +	struct cdns3_device *priv_dev;
>>>>> +	struct cdns3 *cdns = data;
>>>>> +	irqreturn_t ret = IRQ_NONE;
>>>>> +	unsigned long flags;
>>>>> +	u32 reg;
>>>>> +
>>>>> +	priv_dev = cdns->gadget_dev;
>>>>> +	spin_lock_irqsave(&priv_dev->lock, flags);
>>>>
>>>>you're already running in hardirq context. Why do you need this lock at
>>>>all? I would be better to use the hardirq handler to mask your
>>>>interrupts, so they don't fire again, then used the top-half (softirq)
>>>>handler to actually handle the interrupts.
>>>
>>> Yes, spin_lock_irqsave is not necessary here.
>>>
>>> Do you mean replacing devm_request_irq with a request_threaded_irq ?
>>> I have single interrupt line shared between  Host, Driver, DRD/OTG.
>>> I'm not sure if it will work more efficiently.
>>
>>The whole idea for running very little in hardirq context is to give the
>>scheduler a chance to decide what should run. This is important to
>>reduce latency when running with RT patchset applied, for
>>example. However, I'll give you that, it's a minor requirement. It's
>>just that, to me, it's a small detail that's easy to implement.
>
> I will do it in PATCH v2 or PATCH v3.  
> I need to post next version before 24 of December, so if I can do it
> before this date then it will be in PATCH v2. 

Take your time :-) Nothing will happen until next year. I already sent
my pull request for v4.21 and a large chunk of the community takes a few
days off during the holiday season.

There's really no rush from a community stand point.

-- 
balbi

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