On Thu, Sep 19, 2013 at 10:24 PM, Pratyush Anand <pratyush.anand@xxxxxx> wrote: > On Fri, Sep 20, 2013 at 05:37:50AM +0800, Sarah Sharp wrote: >> On Fri, Sep 13, 2013 at 03:50:48PM +0530, Pratyush Anand wrote: >> > On Fri, Sep 13, 2013 at 3:40 PM, Xenia Ragiadakou <burzalodowa@xxxxxxxxx>wrote: >> > > Nope :). There is still Kumar 's patch that keeps the wrappers, so it can >> > > be applied instead of mine. But you did not tell me which tool you use >> > > currently to log the mmio operations? it is useful to know. >> > > >> > > >> > Sorry, I did not use any standard tool, rather I made local changes in >> > dwc3_readl and dwc3_writel to log all dwc3 specific read/write >> > operations into a static array, which was dumped to a text file using >> > an ARM debugger (trace32) for further analysis. >> >> Would it be helpful to add a trace event for xHCI register reads and >> writes (but not a debug statement)? That way you wouldn't have to >> change or recompile the kernel at all, but you could use the trace >> events infrastructure to enable xHCI register read/write debugging. We >> wouldn't flood log files with register reads and writes, but a trace >> event makes sense. > > I have not used tracepoints. So to understand, looked into > Documentation/trace/tracepoints.txt: "When a tracepoint is "on", the > function you provide is called each time the tracepoint is executed." > > So, do you mean to insert tracepoint in xhci_readl/writel? For sure it > would be helpful, but... > Trace ON will be needed only in very special (and a few) case, so > would it be fine to insert a tiny time penalty in readl/writel > routine when trace is off? Not Sure... It's just a series of nops when tracing is off, so the penalty is negligible and is already used in hotter paths in the kernel. > Document says "When a tracepoint is "off" it has no effect, except for > adding a tiny time penalty (checking a condition for a branch)" If anything the "penalty" of xhci_dbg_trace might be something to look at later on since we take what looks like a 1% object size hit. -- Dan -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
