MIPS: Alchemy: Increase minimum timeout for 32kHz timer.

Since a clocksource change post 3.2-rc1, tasks on my DB1500 board
hang after random amounts of time (from a few minutes to a few hours),
regardless of load.  Debugging showed that the compare-match register
value is a few seconds lower than the current counter value.

The minimum value of 8 was initialy determined by a trial-and-error
approach.  Currently it is sufficient for all Alchemys (without PCI
apparently), independent of CPU clock;  only the DB1500 and DB1550
boards experience these timer-related tasks hangs now.

This patch increases the minimum timeout by 1 (to 9 counter ticks)
which seems sufficient since the systems are still working perfectly
fine after over 24 hours.

Signed-off-by: Manuel Lauss <manuel.lauss@googlemail.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3214/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/alchemy/common/time.c b/arch/mips/alchemy/common/time.c
index 7da4d00..a7193ae 100644 (file)
--- a/arch/mips/alchemy/common/time.c
+++ b/arch/mips/alchemy/common/time.c
@@ -146,7 +146,7 @@ static int __init alchemy_time_init(unsigned int m2int)
        cd->shift = 32;
        cd->mult = div_sc(32768, NSEC_PER_SEC, cd->shift);
        cd->max_delta_ns = clockevent_delta2ns(0xffffffff, cd);
-       cd->min_delta_ns = clockevent_delta2ns(8, cd);  /* ~0.25ms */
+       cd->min_delta_ns = clockevent_delta2ns(9, cd);  /* ~0.28ms */
        clockevents_register_device(cd);
        setup_irq(m2int, &au1x_rtcmatch2_irqaction);