On Fri, Aug 27, 2010 at 01:10:55AM -0700, skannan@xxxxxxxxxxxxxx wrote: > > > nack. > > > > Change the name to system_bus_throughput_pm_qos assuming KBS units and > > I'll ok it. It needs to be portable and without units I think drivers > > will start using magic numbers that will break when you go from a > > devices with 16 to 32 bus with the same clock. > > > > We had an email thread about this last year > > http://lkml.org/lkml/2009/12/31/143 > > I don't recall solution ever coming out of it. I think you guys didn't > > like the idea of using units. Further I did post a patch adding > > something like using units. Although I looks like I botch the post the > > linux-pm as I can't seem to find it in the linux-pm archives :( > > http://lkml.org/lkml/2010/4/22/213 > > > > Would you be ok with using throughput instead of a unit less performance > > magic number? > > > > > > --mark > > Ignoring other details for now, the biggest problem with throughput/KBps > units is that PM QoS can't handle it well in its current state. For KBps > the requests should be added together before it's "enforced". Just picking > the maximum won't work optimally. well then current pm_qos code for network throughput takes the max. > Another problem with using KBps is that the available throughput is going > to vary depending on the CPU frequency since the CPU running at a higher > freq is going to use more bandwidth/throughput than the same CPU running > at a lower freq. um, if your modem SPI needs a min freq its really saying it needs a min throughput (throughput is just a scaler times freq, and 8KBS is a 13 bit shift away from HZ for SPI) > A KHz unit will side step both problems. It's not the most ideal in theory > but it's simple and gets the job done since, in our case, there aren't > very many fine grained levels of system bus frequencies (and corresponding > throughputs). I think your getting too wrapped up with this Hz thing and need write a couple of shift macros to convert between Kbs and Hz and be happy. > > I understand that other architectures might have different practical > constraints and abilities and I didn't want to impose the KHz limitation > on them. That's the reason I proposed a parameter whose units is defined > by the "enforcer". The problem is that doing this will result in too many one-off drivers that don't port nicely to my architecture when I use the same peripheral as you. > Thoughts? > not really anything additional, other than I wonder why kbs isn't working for you. Perhaps I'm missing something subtle. --mark -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html