Re: [PATCH LINUX v4 06/13] tty: xuartps: Move request_irq to after setting up the HW

From	Sören Brinkmann <soren.brinkmann@xilinx.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH LINUX v4 06/13] tty: xuartps: Move request_irq to after setting up the HW
Date	2015-12-17 11:10 +0100
Message-ID	<qGDFw-6lt-21@gated-at.bofh.it> (permalink)
References	(2 earlier) <qEhg6-3j4-17@gated-at.bofh.it> <qG01t-68o-49@gated-at.bofh.it> <qG7cC-2o7-15@gated-at.bofh.it> <qGgfU-8gY-9@gated-at.bofh.it> <qGlpf-2W2-11@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Wed, 2015-12-16 at 06:37AM -0800, Peter Hurley wrote:
> On 12/16/2015 01:03 AM, Sören Brinkmann wrote:
> > On Tue, 2015-12-15 at 03:26PM -0800, Peter Hurley wrote:
> >> On 12/15/2015 07:41 AM, Sören Brinkmann wrote:
> >>> On Thu, 2015-12-10 at 01:41PM -0800, Peter Hurley wrote:
> >>>> On 12/05/2015 08:39 PM, Soren Brinkmann wrote:
> >>>>> Request_irq() should be _after_ h/w programming, otherwise an
> >>>>> interrupt could be triggered and in-progress before the h/w has been
> >>>>> setup.
> >>>>
> >>>> Slight misunderstanding. My fault; I should have been more explicit.
> >>>>
> >>>> 1. Any setup necessary for the isr not to be confused and misdirect spurious
> >>>>    interrupts (or hang) should be before installing the isr with request_irq()
> >>>>    None of this code should trigger an interrupt.
> >>>> 2. Clear pending interrupts
> >>>> 3. Install the isr with request_irq()
> >>>> 4. Enable interrupts
> >>>
> >>> Isn't that what the startup function is doing now - more or less. I
> >>> think 3 and 4 are swapped to release the lock and then do the
> >>> request_irq, but I believe that should be OK.
> >>> The startup function configures the HW. Clears the ISR. Enables the
> >>> intended IRQs and then does the request_irq call.
> >>
> >> If the driver enables interrupts before installing the isr with request_irq()
> >> and an interrupt occurs there will the no handler to catch it and EOI the
> >> device.
> > 
> > Really? Shouldn't the IRQ be masked in the interrupt controller until
> > everything is in place?
> 
> Sorry, I'm used to shared interrupts, where that isn't the case.

Ahh, I didn't have to deal with such cases yet. Makes sense though.

	Thanks,
	Sören
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Re: [PATCH LINUX v4 06/13] tty: xuartps: Move request_irq to after  setting up the HW Sören Brinkmann <soren.brinkmann@xilinx.com> - 2015-12-15 16:50 +0100
  Re: [PATCH LINUX v4 06/13] tty: xuartps: Move request_irq to after  setting up the HW Peter Hurley <peter@hurleysoftware.com> - 2015-12-16 00:30 +0100
    Re: [PATCH LINUX v4 06/13] tty: xuartps: Move request_irq to after  setting up the HW Sören Brinkmann <soren.brinkmann@xilinx.com> - 2015-12-16 10:10 +0100
      Re: [PATCH LINUX v4 06/13] tty: xuartps: Move request_irq to after  setting up the HW Peter Hurley <peter@hurleysoftware.com> - 2015-12-16 15:40 +0100
        Re: [PATCH LINUX v4 06/13] tty: xuartps: Move request_irq to after  setting up the HW Sören Brinkmann <soren.brinkmann@xilinx.com> - 2015-12-17 11:10 +0100

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