Messages in this thread | | | Date | Fri, 1 Jan 2016 10:58:06 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH v2 RESEND 1/3] clocksource/vt8500: Use MIN_OSCR_DELTA from PXA |
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On Thu, 31 Dec 2015, Roman Volkov wrote:
> From: Roman Volkov <rvolkov@v1ros.org> > > Since vt8500 and PXA timers are identical, use MIN_OSCR_DELTA from PXA, > which is bigger than existing value. It is required to determine the > minimum delay which hardware can generate.
This changelog makes no sense at all.
> This commit fixes vt8500 breakage in Linux 4.2 introduced by > c6eb3f7 ('hrtimer: Get rid of hrtimer softirq')
> Signed-off-by: Roman Volkov <rvolkov@v1ros.org> > --- > drivers/clocksource/vt8500_timer.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/drivers/clocksource/vt8500_timer.c b/drivers/clocksource/vt8500_timer.c > index a92e94b..dfc3bb4 100644 > --- a/drivers/clocksource/vt8500_timer.c > +++ b/drivers/clocksource/vt8500_timer.c > @@ -50,6 +50,8 @@ > > #define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t) > > +#define MIN_OSCR_DELTA 16 > + > static void __iomem *regbase; > > static cycle_t vt8500_timer_read(struct clocksource *cs) > @@ -80,7 +82,7 @@ static int vt8500_timer_set_next_event(unsigned long cycles, > cpu_relax(); > writel((unsigned long)alarm, regbase + TIMER_MATCH_VAL); > > - if ((signed)(alarm - clocksource.read(&clocksource)) <= 16) > + if ((signed)(alarm - clocksource.read(&clocksource)) <= MIN_OSCR_DELTA)
So how is that value bigger? MIN_OSCR_DELTA is still 16
> return -ETIME; > > writel(1, regbase + TIMER_IER_VAL); > @@ -151,7 +153,7 @@ static void __init vt8500_timer_init(struct device_node *np) > pr_err("%s: setup_irq failed for %s\n", __func__, > clockevent.name); > clockevents_config_and_register(&clockevent, VT8500_TIMER_HZ, > - 4, 0xf0000000); > + MIN_OSCR_DELTA * 2, 0xf0000000);
Now here is the real change. You use a larger minimum tick value so that the above check in vt8500_timer_set_next_event() actually works. That's what you want to explain in the changelog. The blurb about reusing MIN_OSCR_DELTA is just useless.
A proper changelog describes:
1) the problem and the resulting wreckage
2) the solution
Thanks,
tglx
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