On 12/15/2015 07:41 AM, S?ren Brinkmann wrote:

On Thu, 2015-12-10 at 01:41PM -0800, Peter Hurley wrote:

quoted

On 12/05/2015 08:39 PM, Soren Brinkmann wrote:

quoted

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.

quoted

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.

Similar issue.

What I mean is to mask interrupts from this device so that h/w programming
doesn't accidentally trigger an interrupt for which no isr is installed.

It's a bit overkill; that's why I said "extra safety".

Regards,
Peter Hurley

quoted

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.

	S?ren

quoted

Regards,
Peter Hurley

quoted

Reported-by: Peter Hurley <redacted>
Signed-off-by: Soren Brinkmann <redacted>
---
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);
 }
 
 /**