On Wed, May 06, 2015 at 02:36:14AM +0200, Marek Vasut wrote: > On Wednesday, May 06, 2015 at 02:01:35 AM, Dmitry Torokhov wrote: > > On Wed, May 06, 2015 at 01:46:36AM +0200, Marek Vasut wrote: > > > Use msecs_to_jiffies(50) instead of plain (HZ / 50) as the > > > former is independent of kernel HZ settings and provides > > > stable delay. > > > > > > The delay here must be stable, otherwise we might start polling > > > for pen-up event too early. This would in turn render the > > > touchscreen unusable. > > Hi! > > > Doesn't jiffy "size" depend on HZ value? I'd expect the delay be > > "stable" regardless of the value of HZ. > > I have to admit I am not sure, but this would make sense. > > > I do not disagree with the > > patch, but I think you need better justification here (except I think > > the delay should be 20 msec, not 50, and we may use a constant instead > > of reevaluating it all the time). > > Maybe I'm fixing two bugs here ? The problem I really had is that with > kernel HZ set to 250 and the original code, the work was scheduled and > executed too quickly, so my touchscreen was bouncing between pendown and > penup events back and forth, without doing any usaful work. > > I tried changing the code to HZ/5 instead of HZ/50 and that fixes my > issue as well. > > My impression is that using msec_to_jiffies() is clearer especially > if the code is to represent a constant delay. It is indeed clearer and I would not mind such conversion, we just need to adjust the comment why we do that. > But maybe I should then > document why I changed the duration (because the original one was too > short) ? Please make a separate patch for that with separate justification. Thanks! -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
