[PATCH v2 06/15] watchdog: orion: Remove unneeded BRIDGE_CAUSE clear

Sebastian,

On Thu, Jan 23, 2014 at 08:10:49AM -0300, Ezequiel Garcia wrote:

On Thu, Jan 23, 2014 at 12:49:50AM +0100, Sebastian Hesselbarth wrote:
[..]

quoted

quoted

Notice that Ezequiel has added an IRQ handler that just calls panic,
so a spurious interrupt call is VERY VERY BAD.

And I understand that he now clears watchdog's register before
requesting an irq. All that is missing is bridge_irq driver clearing
CAUSE register after masking all irqs, right?

Are you sure clearing the CAUSE register after masking the IRQs will be enough?

AFAICS, until now nobody unmasks the watchdog IRQ (at least the orion_wdt
driver didn't request the interruption) but *still* the CAUSE register is set
upon watchdog expiration. So I would guessed a masked interrupt still raises a
bit in the CAUSE register.

Let me add some real information instead of my speculations. Taken from
the Kirkwood specification:

Table 136: Mbus-L to Mbus Bridge Interrupt Mask Register
Offset:		0x00020114
Field: 		Mask
Type/InitVal: 	RW 0x0
Description:	There is a mask bit per each cause bit. Mask only affects the
		assertion of interrupt pins. It does not affect the setting of
		bits in the Cause register.

So I guess this is why Jason has been insisting with the introduction of
the irq_startup.

(Just for reference, the little patch I attached yesterday proved to work here.)
-- 
Ezequiel Garc?a, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com