DCC(Data Capture and Compare) is a DMA engine designed for debugging
purposes.In case of a system
crash or manual software triggers by the user the DCC hardware stores the value
at the register
addresses which can be used for debugging purposes.The DCC driver provides the
user with sysfs
interface to configure the register addresses.The options that the DCC hardware
provides include
reading from registers,writing to registers,first reading and then writing to
registers and looping
through the values of the same register.
In certain cases a register write needs to be executed for
accessing the rest of the registers,also the user might want to recaord the
changing values of a
particular register with time for which he has the option to use the loop
feature.
The options mentioned above are exposed to the user by sysfs files once the
driver is probed.The
details and usage of this sysfs files are documented in
Documentation/ABI/testing/sysfs-driver-dcc.
As an example if a user wants to configure to store 100 words starting from
address 0x80000050
he should give inputs as following to the sysfs config file:-
echo 0x80000050 100 > /sys/bus/platform/devices/.../config
Similarly if he wants to write to a register using DCC hardware he should give
following input to
config_write sysfs file:-
echo 0x80000000 0xFF > /sys/bus/platform/devices/10a2000.dcc/config_write
This will write the value 0xFF on address 0x80000000.
All this read and write occurs at crash time or if the user manually invokes a
software trigger.
Souradeep Chowdhury (6):
dt-bindings: Added the yaml bindings for DCC
arm64: dts: qcom: sm8150: Add Data Capture and Compare(DCC) support
node
soc: qcom: dcc:Add driver support for Data Capture and Compare
unit(DCC)
soc: qcom: dcc:Add the sysfs variables to the Data Capture and Compare
driver(DCC)
DCC:Added the sysfs entries for DCC(Data Capture and Compare) driver
MAINTAINERS:Added the entry for DCC(Data Capture and Compare) driver
support
Documentation/ABI/testing/sysfs-driver-dcc | 74 +
.../devicetree/bindings/arm/msm/qcom,dcc.yaml | 49 +
MAINTAINERS | 8 +
arch/arm64/boot/dts/qcom/sm8150.dtsi | 7 +
drivers/soc/qcom/Kconfig | 8 +
drivers/soc/qcom/Makefile | 1 +
drivers/soc/qcom/dcc.c | 1574 ++++++++++++++++++++
7 files changed, 1721 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-driver-dcc
create mode 100644 Documentation/devicetree/bindings/arm/msm/qcom,dcc.yaml
create mode 100644 drivers/soc/qcom/dcc.c
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