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

[Sören Brinkmann]

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