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.
>
> For extra safety, first disable interrupts before starting h/w programming.
It's done within spin_lock_irqsave, which gives us at least locally
disabled IRQs. I guess we could add a disabling all IRQs in the UART
core, but it should not really be necessary.
>
> I would do the v5 series in the same order as the v3 series only up to
> what I reviewed. Then do another series with the remainder plus new changes, ok?
Sure.
Sören
>
> Regards,
> Peter Hurley
>
> > Reported-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Soren Brinkmann <soren.brinkmann@xxxxxxxxxx>
> > ---
> > v4:
> > - this patch has been added. Thanks to Peter for pointing it out and providing
> > commit message
> > ---
> > drivers/tty/serial/xilinx_uartps.c | 9 ++-------
> > 1 file changed, 2 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
> > index 6ffd3bbe3e18..1e9053656610 100644
> > --- a/drivers/tty/serial/xilinx_uartps.c
> > +++ b/drivers/tty/serial/xilinx_uartps.c
> > @@ -759,12 +759,7 @@ static void cdns_uart_set_termios(struct uart_port *port,
> > static int cdns_uart_startup(struct uart_port *port)
> > {
> > unsigned long flags;
> > - unsigned int retval = 0, status = 0;
> > -
> > - retval = request_irq(port->irq, cdns_uart_isr, 0, CDNS_UART_NAME,
> > - (void *)port);
> > - if (retval)
> > - return retval;
> > + unsigned int status = 0;
> >
> > spin_lock_irqsave(&port->lock, flags);
> >
> > @@ -818,7 +813,7 @@ static int cdns_uart_startup(struct uart_port *port)
> >
> > spin_unlock_irqrestore(&port->lock, flags);
> >
> > - return retval;
> > + return request_irq(port->irq, cdns_uart_isr, 0, CDNS_UART_NAME, port);
> > }
> >
> > /**
> >
>
--
To unsubscribe from this list: send the line "unsubscribe linux-serial" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
