> From: linux-usb-owner@xxxxxxxxxxxxxxx [mailto:linux-usb-owner@xxxxxxxxxxxxxxx] On Behalf Of Pratyush Anand > Sent: Thursday, September 12, 2013 8:50 PM > > 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. That's easy enough to do with some macro magic in xhci.h. Something like: static inline u32 my_readl(const volatile void __iomem *addr) { u32 value = readl(addr); /* do whatever you want with 'value' here */ return value; } #undef readl #define readl my_readl You just need to make sure no other #include's follow xhci.h that might override your redefinition of readl. I used this technique in the early days of debugging dwc2. -- Paul -- 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
