On 2018-02-01 02:44, Mark Rutland wrote:
On Thu, Jan 25, 2018 at 03:55:12PM -0800, Channagoud Kadabi wrote:
Documentation for last level cache controller device tree bindings,
client bindings usage examples.
Signed-off-by: Channagoud Kadabi <ckadabi@xxxxxxxxxxxxxx>
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.../devicetree/bindings/arm/msm/qcom,llcc.txt | 93
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Documentation/devicetree/bindings/arm/msm/qcom,llcc.txt
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+* LLCC (Last Level Cache Controller)
+
+Properties:
+- compatible:
+ Usage: required
+ Value type: <string>
+ Definition: must be "qcom,llcc-core"
+
+- reg:
+ Usage: required
+ Value Type: <prop-encoded-array>
+ Definition: must be addresses and sizes of the LLCC registers
+
+- llcc-bank-off:
+ Usage: required
+ Value Type: <u32 array>
+ Definition: Offsets of llcc banks from llcc base address starting
from
+ LLCC bank0.
+
+- llcc-broadcast-off:
+ Usage: required
+ Value Type: <u32>
+ Definition: Offset of broadcast register from LLCC bank0 address.
Please could we use "offset" rather than "off" for both of these? That
way it's obvious these aren't properties for disabling some feature.
How variable are these offsets in practice? Is the memory map not
fixed?
The offsets depends on the number of LLCC HW blocks. These number of HW
blocks vary from
chipset to chipset and new registers could be added that changes the
offset.
+
+- #cache-cells:
+ Usage: required
+ Value Type: <u32>
+ Definition: Number of cache cells, must be 1
What's this for, and how is it used?
This is to obtain the phandle arguments from client devices. Related to
cache-slices property.
+
+- max-slices:
+ usage: required
+ Value Type: <u32>
+ Definition: Number of cache slices supported by hardware
+
+- status:
+ Usage: optional
+ Value type: <string>
+ Definition: Property to enable or disable the driver
This is a standard property, so I don't think it needs to be described
here.
Sure, will remove it.
+
+== llcc amon device ==
+
+Properties:
+-qcom,fg-cnt : The value of fine grained counter of activity monitor
+ block.
Could you elaborate on this?
This is counter value programmed in the HW to detect live locks.
This parameter is tunable to avoid false positives.
+
+compatible devices:
+ qcom,sdm845-llcc
Huh? The "qcom,sdm845-llcc" bindings wasn't described above, and it's
not clear what this means.
+
+Example:
+
+ qcom,system-cache@1300000 {
+ compatible = "qcom,llcc-core", "syscon", "simple-mfd";
This looks very wrong. Why do you need syscon and simple-mfd?
LLCC HW block has 3 functionalities:
System cache core, ECC & AMON drivers for debugging.
All three drivers use the same register space for configuration, status
etc.
In order to avoid remapping the same address region across multiple
drivers,
I have implemented this driver as a syncon and simple-mfd.
+ reg = <0x1300000 0x50000>;
+ reg-names = "llcc_base";
+
+ llcc: qcom,sdm845-llcc {
+ compatible = "qcom,sdm845-llcc";
Why is this a sub-node?
qcom,sdm845-llcc: This core driver as mentioned in the list above.
Why isn't the top-level node just "qcom,sdm845-llcc" ?
+ #cache-cells = <1>;
+ max-slices = <32>;
+ };
+
+ qcom,llcc-ecc {
+ compatible = "qcom,llcc-ecc";
+ };
qcom,llcc-ecc: Driver #2 for ECC
+
+ qcom,llcc-amon {
+ compatible = "qcom,llcc-amon";
+ qcom,fg-cnt = <0x7>;
+ };
+
qcom,llcc-amon: Driver #3 for AMON
+ };
+
+== Client ==
+
+Properties:
+- cache-slice-names:
+ Usage: required
+ Value type: <stringlist>
+ Definition: A set of names that identify the usecase names of a
client that uses
+ cache slice. These strings are used to look up the cache slice
+ entries by name.
+
+- cache-slices:
+ Usage: required
+ Value type: <prop-encoded-array>
+ Definition: The tuple has phandle to llcc device as the first
argument and the
+ second argument is the usecase id of the client.
What is a "usecase id" ?
Usecase id for use case that wants to use system cache for eg:
video-encode and video-decode
Is this meant to align with #cache-cells? It would be best to keep a
common prefix (i.e. call that #cache-slice-cells).
Yes. Will update the name.
Thanks,
Mark.
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