On Fri, Mar 17, 2017 at 06:44:03PM +0000, Suzuki K Poulose wrote: > On 17/03/17 15:02, Leo Yan wrote: > >Coresight includes debug module and usually the module connects with CPU > >debug logic. ARMv8 architecture reference manual (ARM DDI 0487A.k) has > >description for related info in "Part H: External Debug". > > > >Chapter H7 "The Sample-based Profiling Extension" introduces several > >sampling registers, e.g. we can check program counter value with > >combined CPU exception level, secure state, etc. So this is helpful for > >analysis CPU lockup scenarios, e.g. if one CPU has run into infinite > >loop with IRQ disabled. In this case the CPU cannot switch context and > >handle any interrupt (including IPIs), as the result it cannot handle > >SMP call for stack dump. > > > >This patch is to enable coresight debug module, so firstly this driver > >is to bind apb clock for debug module and this is to ensure the debug > >module can be accessed from program or external debugger. And the driver > >uses sample-based registers for debug purpose, e.g. when system detects > >the CPU lockup and trigger panic, the driver will dump program counter > > Do we dump it when the CPU lockup is detected with this change ? If not, > we shouldn't claim that here. Right, the mainline kernel missed Colin Cross's patch to trigger panic when detect CPU lockup which used by Android common kernel: http://people.linaro.org/~leo.yan/0001-hardlockup-detect-hard-lockups-without-NMIs-using-se.patch Will fix it. [...] > >+ pr_emerg("\tEDPCSR: [<%p>] %pS\n", (void *)pc, (void *)pc); > > Are we safe calling %pS on the PC, when the PC offset in implementation defined ? I did some quick testing, if cannot find proper kernel symbol for PC value, then %pS will directly output pc value rather than symbol value. Other suggestions are good for me; I will fix for all for them. [...] Thanks, Leo Yan -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
