QCLINUX: qcom-dcc: Add driver support for Data Capture and Compare unit(DCC)

The DCC is a DMA Engine designed to capture and store data during system
crash or software triggers. The DCC operates based on user inputs via
the debugfs interface. The user gives addresses as inputs and these
addresses are stored in the dcc sram. In case of a system crash or a
manual software trigger by the user through the debugfs interface, the
dcc captures and stores the values at these addresses. This patch
contains the driver which has all the methods pertaining to the debugfs
interface, auxiliary functions to support all the four fundamental
operations of dcc namely read, write, read/modify/write and loop. The
probe method here instantiates all the resources necessary for dcc to
operate mainly the dedicated dcc sram where it stores the values. The
DCC driver can be used for debugging purposes without going for a reboot
since it can perform software triggers as well based on user inputs.

Also add the documentation for debugfs entries which explains the
functionalities of each debugfs file that has been created for dcc.

The following is the justification of using debugfs interface over the
other alternatives like sysfs/ioctls

i) As can be seen from the debugfs attribute descriptions, some of the
debugfs attribute files here contains multiple arguments which needs to
be accepted from the user. This goes against the design style of sysfs.

ii) The user input patterns have been made simple and convenient in this
case with the use of debugfs interface as user doesn't need to shuffle
between different files to execute one instruction as was the case on
using other alternatives.

Signed-off-by: Jie Gan <jie.gan@oss.qualcomm.com>

Author: jiegan0107

drivers/misc/Kconfig

@@ -310,6 +310,14 @@ config QCOM_FASTRPC
 	  applications DSP processor. Say M if you want to enable this
 	  module.
 
+config QCOM_DCC
+	tristate "Qualcomm Technologies, Inc. Data Capture and Compare (DCC) engine driver"
+	depends on ARCH_QCOM || COMPILE_TEST
+	help
+	  This option enables the driver for the Data Capture and Compare engine. DCC
+	  driver provides interfaces to configure DCC block and read back the captured
+	  data from the DCC's internal SRAM. The module name for this is qcom-dcc.
+
 config SGI_GRU
 	tristate "SGI GRU driver"
 	depends on X86_UV && SMP

drivers/misc/Makefile

@@ -75,3 +75,4 @@ obj-$(CONFIG_MCHP_LAN966X_PCI)	+= lan966x-pci.o
 obj-y				+= keba/
 obj-y				+= amd-sbi/
 obj-$(CONFIG_MISC_RP1)		+= rp1/
+obj-$(CONFIG_QCOM_DCC)		+= qcom-dcc.o