Hi ksenia, On Fri, Sep 13, 2013 at 04:45:23PM +0800, Xenia Ragiadakou wrote: > On 09/13/2013 06:49 AM, Pratyush Anand wrote: > > On Tue, Sep 10, 2013 at 02:03:15AM +0800, Xenia Ragiadakou wrote: > >> Function xhci_readl() is used to read 32bit xHC registers residing in MMIO > >> address space. It takes as first argument a pointer to the xhci_hcd although > >> it does not use it because internally it simply calls readl. This creates > >> an illusion that xhci_readl() is an xhci specific function that has to be > >> called in a context where a pointer to xhci_hcd is available. > >> This patch replaces calls to xhci_readl() with calls to readl() in xhci-dbg.c. > >> This is done so that xhci_readl() can be removed completely and code can > >> become more straight-forward. > > Its fine that this replacement would simplify it. But, I have > > experienced that sometime such way of reading/writing a peripheral > > registers is quite helpful. I was able to find several issues in dwc3 > > gadget isoc handling quickly because of the availability of dwc3_readl > > dwc3_writel. > > > > With such peripheral specific exerciser one can log all register > > read/write in sequential order with timestamp with a little effort, > > which can further help in debugging critical issues. Sometime, they > > might be even helpful in diagnosis of hardware issues. Same sequence > > can be extracted and provided to hardware engineer for analysing the > > behaviour of device in simulation. > > > > Regards > > Pratyush > > > >> Signed-off-by: Xenia Ragiadakou <burzalodowa@xxxxxxxxx> > > Hi Pratyush, > > The truth is that I did not think of that. What tool do you use to trace > read/write operations for a specific peripheral? I think that you can > trace them using mmiotrace and then filter the output (so that the > address lie within the mmio address space of the particular device you > are interested in). > Mmiotrace reports whether it is read/write, the address, the width in > bytes, the value etc, so you can apply filters to tune your search. > In that case there is no need for a wrapper function around > readl()/writel(), but maybe you have another tool in mind so the wrapper > function will suit better, don't know. But Mmiotrace is supported by x86 arch only. Do you know similar tool for ARM? Regards Pratyush > > best regards, > ksenia -- 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
