Re: [PATCH v4 1/4] dt-bindings: mfd: Add bindings for Ampere Altra SMPro drivers

From: Quan Nguyen
Date: Wed May 05 2021 - 04:44:37 EST

On 01/05/2021 03:19, Rob Herring wrote:
On Thu, Apr 22, 2021 at 04:08:40PM +0700, Quan Nguyen wrote:
Adds device tree bindings for SMPro driver found on the Mt.Jade hardware
reference platform with Ampere's Altra Processor family.

The SMpro co-processor on Ampere Altra processor family is to monitor
and report various data included hwmon-related info, RAS errors, and
other miscellaneous information. This parent SMPro MFD driver creates
a single simple register map to be shared by all sub-devices and leave
all the specific to be handled by the child drivers.

Again, just because you have multiple functions aka MFD, that doesn't
mean you need child nodes for each function. The only thing you have
in DT is a register address. Does this vary? If so, how often? How many
different versions of a DT do you currently or expect to have?

Hi Rob,

Thank you for your review.
I will try to explain what I think below and expect to receive more comments to improve these patches. And if any misundertood, please help correct me.

The idea is to keep the SMPro MFD as a simple generic register map and expect not to change or to handle any specific in this parent device driver. This is why we see the simple_mfd_i2c fit in this case.

And so, all the specific details will be handled in child devices driver and we expect to have child nodes for these child devices. If the child node exist we can then add any specific if necessary later.

One case is that, each socket (ie: the Ampere Altra processor) has it own SMPro co-processor instance in form of register map and each socket could be either slave or master. Some function may not available in slave socket but exist in master socket and we simply choose not to define the child node if that function not existed.

The other case is that if there are multi instances of the same function in one SMPro MFD register map, then each instance might need to be differentiated by using is own register address or maybe a DT property. Then we can simply add them to the node of these instance.

For your specific questions:

+ Does this vary ?
yes, I think so. The register address in each child nodes may vary if the SMPro co-processor firmware change its register map layout or maybe other instances of a function added. Child device drivers are expected to handle these changes if necessary.

+ About how often ?
I actually can't say how often but the purpose of this SMPro register map is to provide the info to the BMC. The BMC will need more info from the host so I think changes will be unavoidable.

Please help with your comments
Thank you,
- Quan


Signed-off-by: Quan Nguyen <quan@xxxxxxxxxxxxxxxxxxxxxx>
---
Changes in v4:
+ Revised the commit message to clarify how the specific info will
be handled commented by Rob.

Changes in v3:
+ Supported list of compatible string [Rob]
+ Introduced reg property in DT to specify reg offset [Rob]
+ Updated description and other minor changes in yaml file [Rob]

Changes in v2:
+ Changed "ampere,ac01-smpro" to "ampere,smpro" [Quan]

.../bindings/hwmon/ampere,ac01-hwmon.yaml | 28 +++++
.../devicetree/bindings/mfd/ampere,smpro.yaml | 105 ++++++++++++++++++
2 files changed, 133 insertions(+)
create mode 100644 Documentation/devicetree/bindings/hwmon/ampere,ac01-hwmon.yaml
create mode 100644 Documentation/devicetree/bindings/mfd/ampere,smpro.yaml

diff --git a/Documentation/devicetree/bindings/hwmon/ampere,ac01-hwmon.yaml b/Documentation/devicetree/bindings/hwmon/ampere,ac01-hwmon.yaml
new file mode 100644
index 000000000000..fbf7ec754160
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwmon/ampere,ac01-hwmon.yaml
@@ -0,0 +1,28 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/hwmon/ampere,ac01-hwmon.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Hardware monitoring driver for the Ampere Altra SMPro
+
+maintainers:
+ - Quan Nguyen <quan@xxxxxxxxxxxxxxxxxxxxxx>
+
+description: |
+ This module is part of the Ampere Altra SMPro multi-function device. For more
+ details see ../mfd/ampere,smpro.yaml.
+
+properties:
+ compatible:
+ enum:
+ - ampere,ac01-hwmon
+
+ reg:
+ maxItems: 1
+
+required:
+ - compatible
+ - reg
+
+additionalProperties: false
diff --git a/Documentation/devicetree/bindings/mfd/ampere,smpro.yaml b/Documentation/devicetree/bindings/mfd/ampere,smpro.yaml
new file mode 100644
index 000000000000..5613c420869e
--- /dev/null
+++ b/Documentation/devicetree/bindings/mfd/ampere,smpro.yaml
@@ -0,0 +1,105 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mfd/ampere,smpro.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Ampere Altra SMPro firmware driver
+
+maintainers:
+ - Quan Nguyen <quan@xxxxxxxxxxxxxxxxxxxxxx>
+
+description: |
+ Ampere Altra SMPro firmware may contain different blocks like hardware
+ monitoring, error monitoring and other miscellaneous features.
+
+properties:
+ compatible:
+ enum:
+ - ampere,smpro
+
+ reg:
+ description:
+ I2C device address.
+ maxItems: 1
+
+ "#address-cells":
+ const: 1
+
+ "#size-cells":
+ const: 0
+
+patternProperties:
+ "^hwmon(@[0-9a-f]+)?$":
+ $ref: ../hwmon/ampere,ac01-hwmon.yaml
+
+ "^misc(@[0-9a-f]+)?$":
+ type: object
+ description: |
+ This module is part of the Ampere Altra SMPro multi-function device
+ to support miscellaneous features
+ properties:
+ compatible:
+ enum:
+ - ampere,ac01-misc
+ reg:
+ maxItems: 1
+
+ required:
+ - compatible
+ - reg
+
+ "^errmon(@[0-9a-f]+)?$":
+ type: object
+ description: |
+ This module is part of the Ampere Altra SMPro multi-function device
+ that supports error monitoring feature.
+
+ properties:
+ compatible:
+ enum:
+ - ampere,ac01-errmon
+ reg:
+ maxItems: 1
+
+ required:
+ - compatible
+ - reg
+
+required:
+ - "#address-cells"
+ - "#size-cells"
+ - compatible
+ - reg
+
+additionalProperties: false
+
+examples:
+ - |
+ i2c {
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ smpro@4f {
+ compatible = "ampere,smpro";
+ reg = <0x4f>;
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ hwmon@10 {
+ compatible = "ampere,ac01-hwmon";
+ reg = <0x10>;
+ };
+
+ misc@b0 {
+ compatible = "ampere,ac01-misc";
+ reg = <0xb0>;
+ };
+
+ errmon@80 {
+ compatible = "ampere,ac01-errmon";
+ reg = <0x80>;
+ };
+
+ };
+ };
--
2.28.0