The code for handling writes to the generic timer control registers
had several bugs:
* ISTATUS (bit 2) is read-only but we forced it to zero on any write
* the check for "was IMASK (bit 1) toggled?" incorrectly used '&' where
it should be '^'
* the handling of IMASK was inverted: we should set the IRQ if
ISTATUS is set and IMASK is clear, not if both are set
The combination of these bugs meant that when running a Linux guest
that uses the generic timers we would fairly quickly end up either
forgetting that the timer output should be asserted, or failing to
set the IRQ when the timer was unmasked. The result is that the guest
never gets any more timer interrupts.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1401803208-1281-1-git-send-email-peter.maydell@linaro.org
Cc: qemu-stable@nongnu.org
(cherry picked from commit d3afacc726)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
27fb65dd1b