ARMv8 architecture reference manual (ARM DDI 0487A.k) Chapter H7 "The Sample-based Profiling Extension" has description for sampling registers, we can utilize these registers to check program counter value with combined CPU exception level, secure state, etc. So this is helpful for CPU lockup bugs, e.g. if one CPU has run into infinite loop with IRQ disabled; the 'hang' CPU cannot switch context and handle any interrupt, so it cannot handle SMP call for stack dump, etc. This patch series is to enable coresight debug module with sample-based registers and register call back notifier for PCSR register dumping when panic happens, so we can see below dumping info for panic; and this patch series has considered the conditions for access permission for debug registers self, so this can avoid access debug registers when CPU power domain is off; the driver also try to figure out the CPU is in secure or non-secure state. ARM external debug module: CPU[0]: EDPRSR: 0000000b (Power:On DLK:Unlock) EDPCSR: [<ffff00000808eb54>] handle_IPI+0xe4/0x150 EDCIDSR: 00000000 EDVIDSR: 90000000 (State:Non-secure Mode:EL1/0 Width:64bits VMID:0) CPU[1]: EDPRSR: 0000000b (Power:On DLK:Unlock) EDPCSR: [<ffff0000087a64c0>] debug_notifier_call+0x108/0x288 EDCIDSR: 00000000 EDVIDSR: 90000000 (State:Non-secure Mode:EL1/0 Width:64bits VMID:0) [...] This patch series has been verified on 96boards Hikey. Changes from RFC: * According to Mike Leach suggestion, added check for EDPRSR to avoid lockup; added supporting EDVIDSR and EDCIDSR registers; * According to Mark Rutland and Mathieu Poirier suggestion, rewrote the documentation for DT binding; * According to Mark and Mathieu suggestion, refined debug driver; Leo Yan (2): coresight: bindings for debug module coresight: add support for debug module .../devicetree/bindings/arm/coresight-debug.txt | 39 ++ drivers/hwtracing/coresight/Kconfig | 10 + drivers/hwtracing/coresight/Makefile | 1 + drivers/hwtracing/coresight/coresight-debug.c | 396 +++++++++++++++++++++ 4 files changed, 446 insertions(+) create mode 100644 Documentation/devicetree/bindings/arm/coresight-debug.txt create mode 100644 drivers/hwtracing/coresight/coresight-debug.c -- 2.7.4 -- 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
