Commit 4cbe60cf authored by Souradeep Chowdhury's avatar Souradeep Chowdhury Committed by Bjorn Andersson
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soc: 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: default avatarSouradeep Chowdhury <quic_schowdhu@quicinc.com>
Reviewed-by: default avatarAlex Elder <elder@linaro.org>
[bjorn: Fixed up a few indents and line wraps]
Signed-off-by: default avatarBjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/644b4f66a358492a8a6738454035c3b120092fe7.1672148732.git.quic_schowdhu@quicinc.com
parent 417091dc

Documentation/ABI/testing/debugfs-driver-dcc

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What:           /sys/kernel/debug/dcc/.../ready

Date:           December 2022

Contact:        Souradeep Chowdhury <quic_schowdhu@quicinc.com>

Description:

		This file is used to check the status of the dcc

		hardware if it's ready to take the inputs. A 'Y'

		here indicates dcc is in a ready condition.

		Example:

		cat /sys/kernel/debug/dcc/.../ready



What:           /sys/kernel/debug/dcc/.../trigger

Date:           December 2022

Contact:        Souradeep Chowdhury <quic_schowdhu@quicinc.com>

Description:

		This is the debugfs interface for manual software

		triggers. The user can simply enter a 1 against

		the debugfs file and enable a manual trigger.

		Example:

		echo  1 > /sys/kernel/debug/dcc/.../trigger



What:           /sys/kernel/debug/dcc/.../config_reset

Date:           December 2022

Contact:        Souradeep Chowdhury <quic_schowdhu@quicinc.com>

Description:

		This file is used to reset the configuration of

		a dcc driver to the default configuration. This

		means that all the previous addresses stored in

		the driver gets removed and user needs to enter

		the address values from the start.

		Example:

		echo  1 > /sys/kernel/debug/dcc/../config_reset



What:           /sys/kernel/debug/dcc/.../[list-number]/config

Date:		 December 2022

Contact:        Souradeep Chowdhury <quic_schowdhu@quicinc.com>

Description:

		This stores the addresses of the registers which

		should be read in case of a hardware crash or

		manual software triggers. The addresses entered here

		are considered under all the 4 types of dcc

		instructions Read type, Write type, Read Modify Write

		type and Loop type. The lists need to be configured

		sequentially and not in a overlapping manner. As an

		example user can jump to list x only after list y is

		configured and enabled. The format for entering all

		types of instructions are explained in examples as

		follows.

		Example:

	         i)Read Type Instruction

		   echo R <1> <2> <3> >/sys/kernel/debug/dcc/../[list-number]/config

		   1->Address to be considered for reading the value.

		   2->The word count of the addresses, read n words

		      starting from address <1>. Each word is of 32 bits.

		      If not entered 1 is considered.

		   3->Can be 'apb' or 'ahb' which indicates if it is apb or ahb

		      bus respectively. If not entered ahb is considered.

		ii)Write Type Instruction

		   echo W <1> <2> <3> > /sys/kernel/debug/dcc/../[list-number]/config

		   1->Address to be considered for writing the value.

		   2->The value that needs to be written at the location.

		   3->Can be a 'apb' or 'ahb' which indicates if it is apb or ahb

		      but respectively.

	       iii)Read Modify Write type instruction

		   echo RW <1> <2> <3> > /sys/kernel/debug/dcc/../[list-number]/config

		   1->The address which needs to be considered for read then write.

		   2->The value that needs to be written on the address.

		   3->The mask of the value to be written.

		iv)Loop Type Instruction

		   echo L <1> <2> <3> > /sys/kernel/debug/dcc/../[list-number]/config

		   1->The loop count, the number of times the value of the addresses will be

		      captured.

		   2->The address count, total number of addresses to be entered in this

		      instruction.

		   3->The series of addresses to be entered separated by a space like <addr1>

		      <addr2>... and so on.



What:           /sys/kernel/debug/dcc/.../[list-number]/enable

Date:           December 2022

Contact:        Souradeep Chowdhury <quic_schowdhu@quicinc.com>

Description:

		This debugfs interface is used for enabling the

		the dcc hardware. Enable file is kept under the

		directory list number for which the user wants

		to enable it. For example if the user wants to

		enable list 1, then he should go for

		echo 1 > /sys/kernel/debug/dcc/.../1/enable.

		On enabling the dcc, all the addresses entered

		by the user for the corresponding list is written

		into dcc sram which is read by the dcc hardware

		on manual or crash induced triggers. Lists should

		be enabled sequentially.For example after configuring

		addresses for list 1 and enabling it, a user can

		proceed to enable list 2 or vice versa.

		Example:

		echo  0 > /sys/kernel/debug/dcc/.../[list-number]/enable

		(disable dcc for the corresponding list number)

		echo  1 > /sys/kernel/debug/dcc/.../[list-number]/enable

		(enable dcc for the corresponding list number)

drivers/soc/qcom/Kconfig

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@@ -70,6 +70,14 @@ config QCOM_LLCC 
	  SDM845. This provides interfaces to clients that use the LLCC.

	  Say yes here to enable LLCC slice driver.



config QCOM_DCC

	tristate "Qualcomm Technologies, Inc. Data Capture and Compare(DCC) engine driver"

	depends on ARCH_QCOM || COMPILE_TEST

	help

	  This option enables driver for Data Capture and Compare engine. DCC

	  driver provides interface to configure DCC block and read back

	  captured data from DCC's internal SRAM.



config QCOM_KRYO_L2_ACCESSORS

	bool

	depends on ARCH_QCOM && ARM64 || COMPILE_TEST

drivers/soc/qcom/Makefile

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@@ -4,6 +4,7 @@ obj-$(CONFIG_QCOM_AOSS_QMP) += qcom_aoss.o 
obj-$(CONFIG_QCOM_GENI_SE) +=	qcom-geni-se.o

obj-$(CONFIG_QCOM_COMMAND_DB) += cmd-db.o

obj-$(CONFIG_QCOM_CPR)		+= cpr.o

obj-$(CONFIG_QCOM_DCC) += dcc.o

obj-$(CONFIG_QCOM_GSBI)	+=	qcom_gsbi.o

obj-$(CONFIG_QCOM_MDT_LOADER)	+= mdt_loader.o

obj-$(CONFIG_QCOM_OCMEM)	+= ocmem.o

drivers/soc/qcom/dcc.c

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