linux-kernel - Re: [PATCH v3] usb: gadget: Add UDC driver for Aeroflex Gaisler GRUSBDC

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Date:	Fri, 13 Dec 2013 13:52:34 -0600
From:	Felipe Balbi <balbi@...com>
To:	Andreas Larsson <andreas@...sler.com>
CC:	<balbi@...com>, <linux-usb@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<software@...sler.com>
Subject: Re: [PATCH v3] usb: gadget: Add UDC driver for Aeroflex Gaisler
 GRUSBDC

Hi,

On Fri, Dec 13, 2013 at 08:48:30AM +0100, Andreas Larsson wrote:
> >On Wed, Dec 04, 2013 at 09:13:58AM +0100, Andreas Larsson wrote:
> >>+static void gr_finish_request(struct gr_ep *ep, struct gr_request *req,
> >>+			      int status)
> >>+{
> >>+	struct gr_udc *dev;
> >>+
> >>+	list_del_init(&req->queue);
> >>+
> >>+	if (likely(req->req.status == -EINPROGRESS))
> >>+		req->req.status = status;
> >>+	else
> >>+		status = req->req.status;
> >>+
> >>+	dev = ep->dev;
> >>+	usb_gadget_unmap_request(&dev->gadget, &req->req, ep->is_in);
> >>+	gr_free_dma_desc_chain(dev, req);
> >>+
> >>+	if (ep->is_in) /* For OUT, actual gets updated bit by bit */
> >>+		req->req.actual = req->req.length;
> >>+
> >>+	if (!status) {
> >>+		if (ep->is_in)
> >>+			gr_dbgprint_request("SENT", ep, req);
> >>+		else
> >>+			gr_dbgprint_request("RECV", ep, req);
> >>+	}
> >>+
> >>+	/* Prevent changes to ep->queue during callback */
> >>+	ep->callback = 1;
> >>+	if (req == dev->ep0reqo && !status) {
> >>+		if (req->setup)
> >>+			gr_ep0_setup(dev, req);
> >>+		else
> >>+			dev_err(dev->dev,
> >>+				"Unexpected non setup packet on ep0in\n");
> >>+	} else if (req->req.complete) {
> >>+		unsigned long flags;
> >>+
> >>+		/*
> >>+		 * Complete should be called with interrupts disabled according
> >>+		 * to the contract of struct usb_request
> >>+		 */
> >>+		local_irq_save(flags);
> >
> >sorry but this driver isn't ready for inclusion. local_irq_save() is a
> >pretty good hint that there's something wrong in the driver. Consider
> >the fact that local_irq_save() will disable preemption even when
> >CONFIG_PREEMPT_FULL is enabled and you have a bit a problem.
> 
> This connection between local_irq_save and CONFIG_PREEMPT_RT_FULL was
> unknown to me. Sure, I can disable interrupts right at spin lock
> time.

that's better.

> >Also, the way you're using thread IRQs is quite wrong. I can't let that
> >pass and get merged upstream, sorry.
> 
> What is quite wrong? What is it that I need to fix?

Ideally the hardirq handler should be usually to actually check if
$this_device generated the IRQ, that should involve reading a IRQSTATUS
register of some sort.

Sure, check that IRQs are actually enabled, but you also need to read
STATUS register before waking the thread up.

-- 
balbi

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