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 debugfs 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 record the changing values of a register with
time for which he has the option to use the loop feature.
The options mentioned above are exposed to the user by debugfs files once the driver
is probed. The details and usage of this debugfs files are documented in
Documentation/ABI/testing/debugfs-driver-dcc.
As an example let us consider a couple of debug scenarios where DCC has been proved to be
effective for debugging purposes:-
i)TimeStamp Related Issue
On SC7180, there was a coresight timestamp issue where it would occasionally be all 0
instead of proper timestamp values.
Proper timestamp:
Idx:3373; ID:10; I_TIMESTAMP : Timestamp.; Updated val = 0x13004d8f5b7aa; CC=0x9e
Zero timestamp:
Idx:3387; ID:10; I_TIMESTAMP : Timestamp.; Updated val = 0x0; CC=0xa2
Now this is a non-fatal issue and doesn't need a system reset, but still needs
to be rootcaused and fixed for those who do care about coresight etm traces.
Since this is a timestamp issue, we would be looking for any timestamp related
clocks and such.
We get all the clk register details from IP documentation and configure it
via DCC config_read debugfs node. Before that we set the current linked list.
/* Program the linked list with the addresses */
echo R 0x10c004 > /sys/kernel/debug/dcc/../3/config
echo R 0x10c008 > /sys/kernel/debug/dcc/../3/config
echo R 0x10c00c > /sys/kernel/debug/dcc/../3/config
echo R 0x10c010 > /sys/kernel/debug/dcc/../3/config
..... and so on for other timestamp related clk registers
/* Other way of specifying is in "addr len" pair, in below case it
specifies to capture 4 words starting 0x10C004 */
echo R 0x10C004 4 > /sys/kernel/debug/dcc/../3/config_read
/* Enable DCC */
echo 1 > /sys/kernel/debug/dcc/../3/enable
/* Run the timestamp test for working case */
/* Send SW trigger */
echo 1 > /sys/kernel/debug/dcc/../trigger
/* Read SRAM */
cat /dev/dcc_sram > dcc_sram1.bin
/* Run the timestamp test for non-working case */
/* Send SW trigger */
echo 1 > /sys/kernel/debug/dcc/../trigger
/* Read SRAM */
cat /dev/dcc_sram > dcc_sram2.bin
Get the parser from [1] and checkout the latest branch.
/* Parse the SRAM bin */
python dcc_parser.py -s dcc_sram1.bin --v2 -o output/
python dcc_parser.py -s dcc_sram2.bin --v2 -o output/
Sample parsed output of dcc_sram1.bin:
<hwioDump version="1">
<timestamp>03/14/21</timestamp>
<generator>Linux DCC Parser</generator>
<chip name="None" version="None">
<register address="0x0010c004" value="0x80000000" />
<register address="0x0010c008" value="0x00000008" />
<register address="0x0010c00c" value="0x80004220" />
<register address="0x0010c010" value="0x80000000" />
</chip>
<next_ll_offset>next_ll_offset : 0x1c </next_ll_offset>
</hwioDump>
ii)NOC register errors
A particular class of registers called NOC which are functional registers was reporting
errors while logging the values.To trace these errors the DCC has been used effectively.
The steps followed were similar to the ones mentioned above.
In addition to NOC registers a few other dependent registers were configured in DCC to
monitor it's values during a crash. A look at the dependent register values revealed that
the crash was happening due to a secured access to one of these dependent registers.
All these debugging activity and finding the root cause was achieved using DCC.
DCC parser is available at the following open source location
https://source.codeaurora.org/quic/la/platform/vendor/qcom-opensource/tools/tree/dcc_parser
Changes in V9
*The comments on version 8 are implemented.
Souradeep Chowdhury (7):
dt-bindings: Added the yaml bindings for DCC
soc: qcom: dcc:Add driver support for Data Capture and Compare
unit(DCC)
MAINTAINERS: Add the entry for DCC(Data Capture and Compare) driver
support
arm64: dts: qcom: sm8150: Add Data Capture and Compare(DCC) support
node
arm64: dts: qcom: sc7280: Add Data Capture and Compare(DCC) support
node
arm64: dts: qcom: sc7180: Add Data Capture and Compare(DCC) support
node
arm64: dts: qcom: sdm845: Add Data Capture and Compare(DCC) support
node
Documentation/ABI/testing/debugfs-driver-dcc | 98 ++
.../devicetree/bindings/arm/msm/qcom,dcc.yaml | 43 +
MAINTAINERS | 8 +
arch/arm64/boot/dts/qcom/sc7180.dtsi | 6 +
arch/arm64/boot/dts/qcom/sc7280.dtsi | 6 +
arch/arm64/boot/dts/qcom/sdm845.dtsi | 6 +
arch/arm64/boot/dts/qcom/sm8150.dtsi | 6 +
drivers/soc/qcom/Kconfig | 8 +
drivers/soc/qcom/Makefile | 1 +
drivers/soc/qcom/dcc.c | 1355 ++++++++++++++++++++
10 files changed, 1537 insertions(+)
create mode 100644 Documentation/ABI/testing/debugfs-driver-dcc
create mode 100644 Documentation/devicetree/bindings/arm/msm/qcom,dcc.yaml
create mode 100644 drivers/soc/qcom/dcc.c
--
2.7.4
Added the entries for all the files added as a part of driver support for
DCC(Data Capture and Compare).
Signed-off-by: Souradeep Chowdhury <[email protected]>
---
MAINTAINERS | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/MAINTAINERS b/MAINTAINERS
index a61f4f3..e57d927 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5146,6 +5146,14 @@ F: include/linux/tfrc.h
F: include/uapi/linux/dccp.h
F: net/dccp/
+DCC QTI DRIVER
+M: Souradeep Chowdhury <[email protected]>
+L: [email protected]
+S: Maintained
+F: Documentation/ABI/testing/debugfs-driver-dcc
+F: Documentation/devicetree/bindings/arm/msm/qcom,dcc.yaml
+F: drivers/soc/qcom/dcc.c
+
DECnet NETWORK LAYER
L: [email protected]
S: Orphan
--
2.7.4
Documentation for Data Capture and Compare(DCC) device tree bindings
in yaml format.
Reviewed-by: Rob Herring <[email protected]>
Signed-off-by: Souradeep Chowdhury <[email protected]>
---
.../devicetree/bindings/arm/msm/qcom,dcc.yaml | 43 ++++++++++++++++++++++
1 file changed, 43 insertions(+)
create mode 100644 Documentation/devicetree/bindings/arm/msm/qcom,dcc.yaml
diff --git a/Documentation/devicetree/bindings/arm/msm/qcom,dcc.yaml b/Documentation/devicetree/bindings/arm/msm/qcom,dcc.yaml
new file mode 100644
index 0000000..b7a6619
--- /dev/null
+++ b/Documentation/devicetree/bindings/arm/msm/qcom,dcc.yaml
@@ -0,0 +1,43 @@
+# SPDX-License-Identifier: (GPL-2.0-or-later OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/arm/msm/qcom,dcc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Data Capture and Compare
+
+maintainers:
+ - Souradeep Chowdhury <[email protected]>
+
+description: |
+ DCC (Data Capture and Compare) is a DMA engine which is used to save
+ configuration data or system memory contents during catastrophic failure
+ or SW trigger. DCC is used to capture and store data for debugging purpose
+properties:
+ compatible:
+ items:
+ - enum:
+ - qcom,sm8150-dcc
+ - qcom,sc7280-dcc
+ - qcom,sc7180-dcc
+ - qcom,sdm845-dcc
+ - const: qcom,dcc
+
+ reg:
+ items:
+ - description: DCC base register region
+ - description: DCC RAM base register region
+
+required:
+ - compatible
+ - reg
+
+additionalProperties: false
+
+examples:
+ - |
+ dma@10a2000{
+ compatible = "qcom,sm8150-dcc","qcom,dcc";
+ reg = <0x010a2000 0x1000>,
+ <0x010ad000 0x2000>;
+ };
--
2.7.4
On Wed, Sep 14, 2022 at 10:31:11PM +0530, Souradeep Chowdhury wrote:
> Documentation for Data Capture and Compare(DCC) device tree bindings
> in yaml format.
>
> Reviewed-by: Rob Herring <[email protected]>
> Signed-off-by: Souradeep Chowdhury <[email protected]>
> ---
> .../devicetree/bindings/arm/msm/qcom,dcc.yaml | 43 ++++++++++++++++++++++
> 1 file changed, 43 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/arm/msm/qcom,dcc.yaml
>
> diff --git a/Documentation/devicetree/bindings/arm/msm/qcom,dcc.yaml b/Documentation/devicetree/bindings/arm/msm/qcom,dcc.yaml
> new file mode 100644
> index 0000000..b7a6619
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/msm/qcom,dcc.yaml
> @@ -0,0 +1,43 @@
> +# SPDX-License-Identifier: (GPL-2.0-or-later OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/arm/msm/qcom,dcc.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Data Capture and Compare
> +
> +maintainers:
> + - Souradeep Chowdhury <[email protected]>
Please update your email address.
> +
> +description: |
> + DCC (Data Capture and Compare) is a DMA engine which is used to save
> + configuration data or system memory contents during catastrophic failure
> + or SW trigger. DCC is used to capture and store data for debugging purpose
An empty line inbetween description and properties would be nice.
> +properties:
> + compatible:
> + items:
> + - enum:
> + - qcom,sm8150-dcc
> + - qcom,sc7280-dcc
> + - qcom,sc7180-dcc
> + - qcom,sdm845-dcc
> + - const: qcom,dcc
> +
> + reg:
> + items:
> + - description: DCC base register region
> + - description: DCC RAM base register region
> +
> +required:
> + - compatible
> + - reg
> +
> +additionalProperties: false
> +
> +examples:
> + - |
> + dma@10a2000{
> + compatible = "qcom,sm8150-dcc","qcom,dcc";
> + reg = <0x010a2000 0x1000>,
> + <0x010ad000 0x2000>;
Please remove the double space between address and size.
Regards,
Bjorn
> + };
> --
> 2.7.4
>
On Wed, 14 Sep 2022 22:31:11 +0530, Souradeep Chowdhury wrote:
> Documentation for Data Capture and Compare(DCC) device tree bindings
> in yaml format.
>
> Reviewed-by: Rob Herring <[email protected]>
> Signed-off-by: Souradeep Chowdhury <[email protected]>
> ---
> .../devicetree/bindings/arm/msm/qcom,dcc.yaml | 43 ++++++++++++++++++++++
> 1 file changed, 43 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/arm/msm/qcom,dcc.yaml
>
My bot found errors running 'make DT_CHECKER_FLAGS=-m dt_binding_check'
on your patch (DT_CHECKER_FLAGS is new in v5.13):
yamllint warnings/errors:
dtschema/dtc warnings/errors:
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/renesas,rzn1-dmamux.example.dtb: dma-router@a0: dma-masters:0: [4294967295, 4294967295] is too long
From schema: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/dma-router.yaml
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/renesas,rzn1-dmamux.example.dtb: dma-router@a0: dma-masters:0: [4294967295, 4294967295] is too long
From schema: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/renesas,rzn1-dmamux.yaml
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/st,stm32-dmamux.example.dtb: dma-router@40020800: dma-masters:0: [4294967295, 4294967295] is too long
From schema: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/dma-router.yaml
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/st,stm32-dmamux.example.dtb: dma-router@40020800: dma-masters:0: [4294967295, 4294967295] is too long
From schema: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/st,stm32-dmamux.yaml
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/st,stm32-dmamux.example.dtb: dma-router@40020800: Unevaluated properties are not allowed ('dma-channels', 'dma-masters', 'dma-requests' were unexpected)
From schema: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/st,stm32-dmamux.yaml
doc reference errors (make refcheckdocs):
See https://patchwork.ozlabs.org/patch/
This check can fail if there are any dependencies. The base for a patch
series is generally the most recent rc1.
If you already ran 'make dt_binding_check' and didn't see the above
error(s), then make sure 'yamllint' is installed and dt-schema is up to
date:
pip3 install dtschema --upgrade
Please check and re-submit.
On 9/15/2022 9:05 AM, Bjorn Andersson wrote:
> On Wed, Sep 14, 2022 at 10:31:11PM +0530, Souradeep Chowdhury wrote:
>> Documentation for Data Capture and Compare(DCC) device tree bindings
>> in yaml format.
>>
>> Reviewed-by: Rob Herring <[email protected]>
>> Signed-off-by: Souradeep Chowdhury <[email protected]>
>> ---
>> .../devicetree/bindings/arm/msm/qcom,dcc.yaml | 43 ++++++++++++++++++++++
>> 1 file changed, 43 insertions(+)
>> create mode 100644 Documentation/devicetree/bindings/arm/msm/qcom,dcc.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/arm/msm/qcom,dcc.yaml b/Documentation/devicetree/bindings/arm/msm/qcom,dcc.yaml
>> new file mode 100644
>> index 0000000..b7a6619
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/arm/msm/qcom,dcc.yaml
>> @@ -0,0 +1,43 @@
>> +# SPDX-License-Identifier: (GPL-2.0-or-later OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/arm/msm/qcom,dcc.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Data Capture and Compare
>> +
>> +maintainers:
>> + - Souradeep Chowdhury <[email protected]>
> Please update your email address.
Ack
>
>> +
>> +description: |
>> + DCC (Data Capture and Compare) is a DMA engine which is used to save
>> + configuration data or system memory contents during catastrophic failure
>> + or SW trigger. DCC is used to capture and store data for debugging purpose
> An empty line inbetween description and properties would be nice.
Ack
>
>> +properties:
>> + compatible:
>> + items:
>> + - enum:
>> + - qcom,sm8150-dcc
>> + - qcom,sc7280-dcc
>> + - qcom,sc7180-dcc
>> + - qcom,sdm845-dcc
>> + - const: qcom,dcc
>> +
>> + reg:
>> + items:
>> + - description: DCC base register region
>> + - description: DCC RAM base register region
>> +
>> +required:
>> + - compatible
>> + - reg
>> +
>> +additionalProperties: false
>> +
>> +examples:
>> + - |
>> + dma@10a2000{
>> + compatible = "qcom,sm8150-dcc","qcom,dcc";
>> + reg = <0x010a2000 0x1000>,
>> + <0x010ad000 0x2000>;
> Please remove the double space between address and size.
Ack
>
> Regards,
> Bjorn
>
>
>> + };
>> --
>> 2.7.4
>>
On Thu, Sep 15, 2022 at 05:06:29PM +0530, Souradeep Chowdhury wrote:
>
> On 9/15/2022 3:07 PM, Krzysztof Kozlowski wrote:
> > On Wed, 14 Sep 2022 22:31:11 +0530, Souradeep Chowdhury wrote:
> > > Documentation for Data Capture and Compare(DCC) device tree bindings
> > > in yaml format.
> > >
> > > Reviewed-by: Rob Herring <[email protected]>
> > > Signed-off-by: Souradeep Chowdhury <[email protected]>
> > > ---
> > > .../devicetree/bindings/arm/msm/qcom,dcc.yaml | 43 ++++++++++++++++++++++
> > > 1 file changed, 43 insertions(+)
> > > create mode 100644 Documentation/devicetree/bindings/arm/msm/qcom,dcc.yaml
> > >
> > My bot found errors running 'make DT_CHECKER_FLAGS=-m dt_binding_check'
> > on your patch (DT_CHECKER_FLAGS is new in v5.13):
> >
> > yamllint warnings/errors:
> >
> > dtschema/dtc warnings/errors:
> > /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/renesas,rzn1-dmamux.example.dtb: dma-router@a0: dma-masters:0: [4294967295, 4294967295] is too long
> > From schema: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/dma-router.yaml
> > /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/renesas,rzn1-dmamux.example.dtb: dma-router@a0: dma-masters:0: [4294967295, 4294967295] is too long
> > From schema: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/renesas,rzn1-dmamux.yaml
> > /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/st,stm32-dmamux.example.dtb: dma-router@40020800: dma-masters:0: [4294967295, 4294967295] is too long
> > From schema: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/dma-router.yaml
> > /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/st,stm32-dmamux.example.dtb: dma-router@40020800: dma-masters:0: [4294967295, 4294967295] is too long
> > From schema: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/st,stm32-dmamux.yaml
> > /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/st,stm32-dmamux.example.dtb: dma-router@40020800: Unevaluated properties are not allowed ('dma-channels', 'dma-masters', 'dma-requests' were unexpected)
> > From schema: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/st,stm32-dmamux.yaml
> >
> > doc reference errors (make refcheckdocs):
> >
> > See https://patchwork.ozlabs.org/patch/
> >
> > This check can fail if there are any dependencies. The base for a patch
> > series is generally the most recent rc1.
> >
> > If you already ran 'make dt_binding_check' and didn't see the above
> > error(s), then make sure 'yamllint' is installed and dt-schema is up to
> > date:
> >
> > pip3 install dtschema --upgrade
> >
> > Please check and re-submit.
> This reported error is unrelated to my yaml file. Kindly check from your
> end.
Yes, you can ignore it.
Rob
On 9/15/2022 3:07 PM, Krzysztof Kozlowski wrote:
> On Wed, 14 Sep 2022 22:31:11 +0530, Souradeep Chowdhury wrote:
>> Documentation for Data Capture and Compare(DCC) device tree bindings
>> in yaml format.
>>
>> Reviewed-by: Rob Herring <[email protected]>
>> Signed-off-by: Souradeep Chowdhury <[email protected]>
>> ---
>> .../devicetree/bindings/arm/msm/qcom,dcc.yaml | 43 ++++++++++++++++++++++
>> 1 file changed, 43 insertions(+)
>> create mode 100644 Documentation/devicetree/bindings/arm/msm/qcom,dcc.yaml
>>
> My bot found errors running 'make DT_CHECKER_FLAGS=-m dt_binding_check'
> on your patch (DT_CHECKER_FLAGS is new in v5.13):
>
> yamllint warnings/errors:
>
> dtschema/dtc warnings/errors:
> /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/renesas,rzn1-dmamux.example.dtb: dma-router@a0: dma-masters:0: [4294967295, 4294967295] is too long
> From schema: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/dma-router.yaml
> /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/renesas,rzn1-dmamux.example.dtb: dma-router@a0: dma-masters:0: [4294967295, 4294967295] is too long
> From schema: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/renesas,rzn1-dmamux.yaml
> /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/st,stm32-dmamux.example.dtb: dma-router@40020800: dma-masters:0: [4294967295, 4294967295] is too long
> From schema: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/dma-router.yaml
> /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/st,stm32-dmamux.example.dtb: dma-router@40020800: dma-masters:0: [4294967295, 4294967295] is too long
> From schema: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/st,stm32-dmamux.yaml
> /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/st,stm32-dmamux.example.dtb: dma-router@40020800: Unevaluated properties are not allowed ('dma-channels', 'dma-masters', 'dma-requests' were unexpected)
> From schema: /builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/dma/st,stm32-dmamux.yaml
>
> doc reference errors (make refcheckdocs):
>
> See https://patchwork.ozlabs.org/patch/
>
> This check can fail if there are any dependencies. The base for a patch
> series is generally the most recent rc1.
>
> If you already ran 'make dt_binding_check' and didn't see the above
> error(s), then make sure 'yamllint' is installed and dt-schema is up to
> date:
>
> pip3 install dtschema --upgrade
>
> Please check and re-submit.
This reported error is unrelated to my yaml file. Kindly check from your
end.