[PATCH v7 0/7] coresight: enable debug module

From: Leo Yan
Date: Tue May 02 2017 - 04:30:44 EST

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.

Patch 0001 is to document the dt binding; patch 0002 is to document
boot parameters used in kernel command line and add one detailed
document to describe the Coresight debug module implementation, the
clock and power domain impaction on the driver, some examples for

Patch 0003 is used to fix the func of_get_coresight_platform_data()
doesn't properly drop the reference to the CPU node pointer; and
patch 0004 is refactor to add new function of_coresight_get_cpu().

Patch 0005 is the driver for CPU debug module.

Patch 0006 in this series are to enable debug unit on 96boards Hikey,
Patch 0007 is to enable debug on 96boards DB410c. Have verified on both
two boards.

We can enable debugging with two methods, adding parameters into kernel
command line for build-in module:

Or we can wait the system has booted up to use debugfs nodes to enable
# echo 1 > /sys/kernel/debug/coresight_cpu_debug/enable

As result we can get below log after input command:
echo c > /proc/sysrq-trigger:

ARM external debug module:
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)
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)


Changes from v6:
* According to Suzuki and Mathieu suggestions, refined debug module
driver to install panic notifier when insmod module; refined function
debug_force_cpu_powered_up() for CPU power state checking; some minor
fixing for output log, adding comments for memory barrier, code

Changes from v5:
* According to Suzuki and Mathieu suggestions, refined debug module
driver to drop unused structure members, refactored initialization
code to distinguish hardware implementation features, refactored
flow for forcing CPU powered up, supported pm_runtime operations.
* Added one new doc file: Documentation/trace/coresight-cpu-debug.txt,
which is used to describe detailed info for implementation, clock
and power domain impaction on debug module, and exmaples for common
* Removed "idle constraints" from debug driver.

Changes from v4:
* This version is mainly credit to ARM colleagues many contribution
ideas for better quality (Thanks a lot Suzuki, Mike and Sudeep!).
* According to Suzuki suggestion, refined debug module driver to avoid
memory leak for drvdata struct, handle PCSAMPLE_MODE=1, use flag
drvdata.pc_has_offset to indicate if PCSR has offset, minor fixes.
* According to Mathieu suggestion, refined dt binding description.
* Changed driver to support module mode;
* According to Mike suggestion and very appreciate the pseudo code,
added support to force CPU powered up with register EDPRCR;
* According to discussions, added command line and debugfs nodes to
support enabling debugging for boot time, or later can dynamically
enable/disable debugging by debugfs.
* According to Rob Herring suggestion, one minor fixes in DT binding.
* According to Stephen Boyd suggestion, add const quality to structure
device_node. And used use of_cpu_device_node_get() to replace
of_get_cpu_node() in patch 0003.

Changes from v3:
* Added Suzuki K Poulose's patch to fix issue for the func
of_get_coresight_platform_data() doesn't properly drop the reference
to the CPU node pointer.
* According to Suzuki suggestion, added code to handl the corner case
for ARMv8 CPU with aarch32 mode.
* According to Suzuki suggestion, changed compatible string to
* According to Mathieu suggestion, added "power-domains" as optional

Changes from v2:
* According to Mathieu Poirier suggestion, applied some minor fixes.
* Added two extra patches for enabling debug module on Hikey.

Changes from v1:
* According to Mike Leach suggestion, removed the binding for debug
module clocks which have been directly provided by CPU clocks.
* According to Mathieu Poirier suggestion, added function
of_coresight_get_cpu() and some minor refactors for debug module

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 (6):
coresight: bindings for CPU debug module
doc: Add documentation for Coresight CPU debug
coresight: refactor with function of_coresight_get_cpu
coresight: add support for CPU debug module
arm64: dts: hi6220: register debug module
arm64: dts: qcom: msm8916: Add debug unit

Suzuki K Poulose (1):
coresight: of_get_coresight_platform_data: Add missing of_node_put

Documentation/admin-guide/kernel-parameters.txt | 7 +
.../bindings/arm/coresight-cpu-debug.txt | 49 ++
Documentation/trace/coresight-cpu-debug.txt | 174 ++++++
arch/arm64/boot/dts/hisilicon/hi6220.dtsi | 64 ++
arch/arm64/boot/dts/qcom/msm8916.dtsi | 32 +
drivers/hwtracing/coresight/Kconfig | 14 +
drivers/hwtracing/coresight/Makefile | 1 +
drivers/hwtracing/coresight/coresight-cpu-debug.c | 671 +++++++++++++++++++++
drivers/hwtracing/coresight/of_coresight.c | 40 +-
include/linux/coresight.h | 2 +
10 files changed, 1042 insertions(+), 12 deletions(-)
create mode 100644 Documentation/devicetree/bindings/arm/coresight-cpu-debug.txt
create mode 100644 Documentation/trace/coresight-cpu-debug.txt
create mode 100644 drivers/hwtracing/coresight/coresight-cpu-debug.c