[PATCH v4 0/7] hwmon: (nct6775) Convert to regmap, add i2c support

[PATCH v4 0/7] hwmon: (nct6775) Convert to regmap, add i2c support

[Zev Weiss]

Hello,

This is v4 of my effort to add i2c support to the nct6775 hwmon
driver.

Changes since v3 [0]:
 - Reverted to dedicated DT binding file, added
   nuvoton,tsi-channel-mask property and support for it to the i2c
   driver
 - Reverted file names to the ones in v2 [Guenter]
 - Added patch 5 converting S_I* permissions macros to octal [Guenter]
 - R-B tags from Joel on patches 2-4
 - Tiny comment-formatting tweak to appease checkpatch on patch 6

Changes since v2 [1]:
 - Fixed wrong parenthesization in nct6775_write_value()
 - Moved DT binding to trivial-devices.yml instead of a dedicated file
   [Guenter]
 - Renamed drivers and Kconfig symbols to keep existing platform
   driver as "nct6775" (SENSORS_NCT6775) and the core module as
   "nct6775-core" (SENSORS_NCT6775_CORE) [Guenter]
 - Fixed SENSORS_NCT6775_CORE Kconfig to select REGMAP, removed
   erroneous REGMAP_I2C selection from SENSORS_NCT6775_I2C [Guenter]

Changes since v1 [2]:
 - Added preparatory patch converting driver to regmap API [Guenter]
 - Replaced ENOSPC with ENOBUFS and removed WARN_ON() in
   nct6775_add_attr_group() [Guenter]
 - Added dedicated symbol namespace [Guenter]
 - Removed nct6775_write_temp() and nct6775_update_device() symbol
   exports [Guenter]
 - Reordered patches to put dt-bindings patch first [Krzysztof]

[0] https://lore.kernel.org/openbmc/20220426071848.11619-1-zev@bewilderbeest.net/
[1] https://lore.kernel.org/linux-hwmon/20220309005047.5107-1-zev@bewilderbeest.net/
[2] https://lore.kernel.org/linux-hwmon/20220226133047.6226-1-zev@bewilderbeest.net/

A slightly edited version of the previous cover letter follows:


This patch series augments the existing nct6775 driver with support
for the hardware's i2c interface; along the way it converts the driver
to use the regmap API, and splits the LPC-specific platform driver
into a separate module from the interface-independent core.

Thus far the nct6775 driver has only supported the LPC interface,
which is the main interface by which the Super-I/O chip is typically
connected to the host (x86) processor.

However, these chips also provide an i2c interface, which can provide
a way for a BMC to also monitor sensor readings from them.  On some
systems (such as the ASRock Rack ROMED8HM3 and X570-D4U) this may be
the only way for the BMC to monitor host CPU temperatures (e.g. to
indirectly access a TSI interface); this functionality is thus an
important component of enabling OpenBMC to support such systems.

In such an arrangement the Super-I/O chip is simultaneously controlled
by two independent processors (the host and the BMC) which typically
do not coordinate their accesses with each other.  In order to avoid
conflicts between the two, the i2c driver avoids all writes to the
device, since the BMC's needs with the hardware are merely that it be
able to retrieve sensor readings.  This allows the host processor to
remain ultimately in control of the chip and unaware of the BMC's use
of it at all.

The sole exception to the "no writes" rule for the i2c driver is for
the bank-select register -- while I haven't been able to find any
explicit statement in the Nuvoton datasheets guaranteeing this,
testing via manual register accesses (as detailed in [3]) has
indicated that, as one might hope, the i2c interface has its own
bank-select register independent of the one used by the LPC interface.

In terms of code structure, the approach taken in this series is to
first convert the driver's register accesses to the regmap API, and
then split the LPC-specific parts of it out into a separate module
(retaining the current "nct6775" name), leaving the
interface-independent parts in a generic driver (called nct6775-core).
The nct6775-i2c driver is then added as an additional consumer of the
nct6775-core module's functionality (essentially just providing its
own set of regmap read/write callback functions).

The first patch adds the chips supported by the nct6775 driver to
Documentation/device-tree-bindings/trivial-devices.yml.  The second
patch contains the change to convert all register accesses to use a
regmap.  The third and fourth patches make some relatively small
infrastructural changes to the driver, and the fifth cleans up a bunch
of checkpatch complaints prior to the main split patch.  The
core/platform driver split is in the sixth patch, and the final patch
adds the i2c driver itself.

The nct6775 and nct6775-i2c drivers have both been tested on the
NCT6779D in an ASRock ROMED8HM3 system and the NCT6798 [4] in an
ASRock X570-D4U (the latter thanks to Renze, CCed); both seem to work
as expected on both systems.  I don't have access to any asuswmi
hardware, so testing of the nct6775-platform driver on that to ensure
it doesn't break there would be appreciated (Oleksandr, perhaps?).


Thanks,
Zev

[3] https://lore.kernel.org/linux-hwmon/YhttzgDtGpcTniyw@hatter.bewilderbeest.net/
[4] Though it's physically labeled (mislabeled?) as an NCT6796, for
    what that's worth.

Zev Weiss (7):
  dt-bindings: hwmon: Add nuvoton,nct6775
  hwmon: (nct6775) Convert register access to regmap API
  hwmon: (nct6775) Rearrange attr-group initialization
  hwmon: (nct6775) Add read-only mode
  hwmon: (nct6775) Convert S_I* permissions macros to octal
  hwmon: (nct6775) Split core and platform driver
  hwmon: (nct6775) Add i2c driver

 .../bindings/hwmon/nuvoton,nct6775.yaml       |   56 +
 MAINTAINERS                                   |   12 +-
 drivers/hwmon/Kconfig                         |   31 +-
 drivers/hwmon/Makefile                        |    3 +
 drivers/hwmon/{nct6775.c => nct6775-core.c}   | 2445 +++++------------
 drivers/hwmon/nct6775-i2c.c                   |  195 ++
 drivers/hwmon/nct6775-platform.c              | 1226 +++++++++
 drivers/hwmon/nct6775.h                       |  252 ++
 8 files changed, 2455 insertions(+), 1765 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/hwmon/nuvoton,nct6775.yaml
 rename drivers/hwmon/{nct6775.c => nct6775-core.c} (66%)
 create mode 100644 drivers/hwmon/nct6775-i2c.c
 create mode 100644 drivers/hwmon/nct6775-platform.c
 create mode 100644 drivers/hwmon/nct6775.h

-- 
2.36.0

[PATCH v4 1/7] dt-bindings: hwmon: Add nuvoton,nct6775

[Zev Weiss]

These Super I/O chips have an i2c interface that some systems expose
to a BMC; the BMC's device tree can now describe that via this
binding.

Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
---
 .../bindings/hwmon/nuvoton,nct6775.yaml       | 56 +++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/nuvoton,nct6775.yaml

diff --git a/Documentation/devicetree/bindings/hwmon/nuvoton,nct6775.yaml b/Documentation/devicetree/bindings/hwmon/nuvoton,nct6775.yaml
new file mode 100644
index 000000000000..418477374fdb
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwmon/nuvoton,nct6775.yaml
@@ -0,0 +1,56 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+
+$id: http://devicetree.org/schemas/hwmon/nuvoton,nct6775.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Nuvoton NCT6775 and compatible Super I/O chips
+
+maintainers:
+  - Zev Weiss <zev@bewilderbeest.net>
+
+properties:
+  compatible:
+    enum:
+      - nuvoton,nct6106
+      - nuvoton,nct6116
+      - nuvoton,nct6775
+      - nuvoton,nct6776
+      - nuvoton,nct6779
+      - nuvoton,nct6791
+      - nuvoton,nct6792
+      - nuvoton,nct6793
+      - nuvoton,nct6795
+      - nuvoton,nct6796
+      - nuvoton,nct6797
+      - nuvoton,nct6798
+
+  reg:
+    maxItems: 1
+
+  nuvoton,tsi-channel-mask:
+    description:
+      Bitmask indicating which TSI temperature sensor channels are
+      active.  LSB is TSI0, bit 1 is TSI1, etc.
+    maximum: 0xff
+    default: 0
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        superio@4d {
+            compatible = "nuvoton,nct6779";
+            reg = <0x4d>;
+            nuvoton,tsi-channel-mask = <0x03>;
+        };
+    };
-- 
2.36.0

Re: [PATCH v4 1/7] dt-bindings: hwmon: Add nuvoton,nct6775

[Krzysztof Kozlowski]

On 27/04/2022 03:01, Zev Weiss wrote:
> These Super I/O chips have an i2c interface that some systems expose
> to a BMC; the BMC's device tree can now describe that via this
> binding.
> 
> Signed-off-by: Zev Weiss <zev@bewilderbeest.net>

I already reviewed it so I guess you did not include the tag because of
significant changes?

> ---
>  .../bindings/hwmon/nuvoton,nct6775.yaml       | 56 +++++++++++++++++++
>  1 file changed, 56 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/hwmon/nuvoton,nct6775.yaml
> 
> diff --git a/Documentation/devicetree/bindings/hwmon/nuvoton,nct6775.yaml b/Documentation/devicetree/bindings/hwmon/nuvoton,nct6775.yaml
> new file mode 100644
> index 000000000000..418477374fdb
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/hwmon/nuvoton,nct6775.yaml
> @@ -0,0 +1,56 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +
> +$id: http://devicetree.org/schemas/hwmon/nuvoton,nct6775.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Nuvoton NCT6775 and compatible Super I/O chips
> +
> +maintainers:
> +  - Zev Weiss <zev@bewilderbeest.net>
> +
> +properties:
> +  compatible:
> +    enum:
> +      - nuvoton,nct6106
> +      - nuvoton,nct6116
> +      - nuvoton,nct6775
> +      - nuvoton,nct6776
> +      - nuvoton,nct6779
> +      - nuvoton,nct6791
> +      - nuvoton,nct6792
> +      - nuvoton,nct6793
> +      - nuvoton,nct6795
> +      - nuvoton,nct6796
> +      - nuvoton,nct6797
> +      - nuvoton,nct6798
> +
> +  reg:
> +    maxItems: 1
> +
> +  nuvoton,tsi-channel-mask:
> +    description:
> +      Bitmask indicating which TSI temperature sensor channels are
> +      active.  LSB is TSI0, bit 1 is TSI1, etc.

Need a type/ref.

> +    maximum: 0xff
> +    default: 0

Since by default it is disabled, doesn't it make a required property?
IOW, if you add a node without this mask, will the device operate
properly and usefully?




Best regards,
Krzysztof

Re: [PATCH v4 1/7] dt-bindings: hwmon: Add nuvoton,nct6775

[Zev Weiss]

On Tue, Apr 26, 2022 at 11:04:30PM PDT, Krzysztof Kozlowski wrote:
>On 27/04/2022 03:01, Zev Weiss wrote:
>> These Super I/O chips have an i2c interface that some systems expose
>> to a BMC; the BMC's device tree can now describe that via this
>> binding.
>>
>> Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
>
>I already reviewed it so I guess you did not include the tag because of
>significant changes?
>

Yeah, the nuvoton,tsi-channel-mask property is new this round, so I 
dropped the previous R-B -- and since it looks like I missed some stuff, 
thanks for taking another look (though perhaps some of it could have 
been avoided if I'd remembered to run 'make dt_binding_check').

>> ---
>>  .../bindings/hwmon/nuvoton,nct6775.yaml       | 56 +++++++++++++++++++
>>  1 file changed, 56 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/hwmon/nuvoton,nct6775.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/hwmon/nuvoton,nct6775.yaml b/Documentation/devicetree/bindings/hwmon/nuvoton,nct6775.yaml
>> new file mode 100644
>> index 000000000000..418477374fdb
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/hwmon/nuvoton,nct6775.yaml
>> @@ -0,0 +1,56 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +
>> +$id: http://devicetree.org/schemas/hwmon/nuvoton,nct6775.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Nuvoton NCT6775 and compatible Super I/O chips
>> +
>> +maintainers:
>> +  - Zev Weiss <zev@bewilderbeest.net>
>> +
>> +properties:
>> +  compatible:
>> +    enum:
>> +      - nuvoton,nct6106
>> +      - nuvoton,nct6116
>> +      - nuvoton,nct6775
>> +      - nuvoton,nct6776
>> +      - nuvoton,nct6779
>> +      - nuvoton,nct6791
>> +      - nuvoton,nct6792
>> +      - nuvoton,nct6793
>> +      - nuvoton,nct6795
>> +      - nuvoton,nct6796
>> +      - nuvoton,nct6797
>> +      - nuvoton,nct6798
>> +
>> +  reg:
>> +    maxItems: 1
>> +
>> +  nuvoton,tsi-channel-mask:
>> +    description:
>> +      Bitmask indicating which TSI temperature sensor channels are
>> +      active.  LSB is TSI0, bit 1 is TSI1, etc.
>
>Need a type/ref.
>

Ack, thanks.

>> +    maximum: 0xff
>> +    default: 0
>
>Since by default it is disabled, doesn't it make a required property?
>IOW, if you add a node without this mask, will the device operate
>properly and usefully?
>

Yeah, zero active TSI channels is a totally legitimate way for these 
devices to operate.  TSI is just an optional source of additional 
temperature readings that's used on some (AMD) systems; all the basic 
Super I/O functionality works fine without it.


Thanks,
Zev

Re: [PATCH v4 1/7] dt-bindings: hwmon: Add nuvoton,nct6775

[Krzysztof Kozlowski]

On 27/04/2022 08:44, Zev Weiss wrote:
> 
>>> +    maximum: 0xff
>>> +    default: 0
>>
>> Since by default it is disabled, doesn't it make a required property?
>> IOW, if you add a node without this mask, will the device operate
>> properly and usefully?
>>
> 
> Yeah, zero active TSI channels is a totally legitimate way for these 
> devices to operate.  TSI is just an optional source of additional 
> temperature readings that's used on some (AMD) systems; all the basic 
> Super I/O functionality works fine without it.


OK, thanks.


Best regards,
Krzysztof

Re: [PATCH v4 0/7] hwmon: (nct6775) Convert to regmap, add i2c support

[Guenter Roeck]

Hi Zev,

On 4/26/22 18:01, Zev Weiss wrote:
> Hello,
> 
> This is v4 of my effort to add i2c support to the nct6775 hwmon
> driver.
> 

Thanks a lot for your effort.

I applied patches 2..6 to hwmon-next. The first and the last
patch of the series will have to wait for DT maintainer approval.

Thanks,
Guenter

Re: [PATCH v4 1/7] dt-bindings: hwmon: Add nuvoton,nct6775

[Rob Herring]

On Tue, 26 Apr 2022 18:01:48 -0700, Zev Weiss wrote:
> These Super I/O chips have an i2c interface that some systems expose
> to a BMC; the BMC's device tree can now describe that via this
> binding.
> 
> Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
> ---
>  .../bindings/hwmon/nuvoton,nct6775.yaml       | 56 +++++++++++++++++++
>  1 file changed, 56 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/hwmon/nuvoton,nct6775.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/linux-dt-review/Documentation/devicetree/bindings/hwmon/nuvoton,nct6775.yaml: properties:nuvoton,tsi-channel-mask: 'oneOf' conditional failed, one must be fixed:
	'type' is a required property
		hint: A vendor boolean property can use "type: boolean"
	Additional properties are not allowed ('default', 'maximum' were unexpected)
		hint: A vendor boolean property can use "type: boolean"
	/builds/robherring/linux-dt-review/Documentation/devicetree/bindings/hwmon/nuvoton,nct6775.yaml: properties:nuvoton,tsi-channel-mask: 'oneOf' conditional failed, one must be fixed:
		'enum' is a required property
		'const' is a required property
		hint: A vendor string property with exact values has an implicit type
		from schema $id: http://devicetree.org/meta-schemas/vendor-props.yaml#
	/builds/robherring/linux-dt-review/Documentation/devicetree/bindings/hwmon/nuvoton,nct6775.yaml: properties:nuvoton,tsi-channel-mask: 'oneOf' conditional failed, one must be fixed:
		'$ref' is a required property
		'allOf' is a required property
		hint: A vendor property needs a $ref to types.yaml
		from schema $id: http://devicetree.org/meta-schemas/vendor-props.yaml#
	hint: Vendor specific properties must have a type and description unless they have a defined, common suffix.
	from schema $id: http://devicetree.org/meta-schemas/vendor-props.yaml#
/builds/robherring/linux-dt-review/Documentation/devicetree/bindings/hwmon/nuvoton,nct6775.yaml: ignoring, error in schema: properties: nuvoton,tsi-channel-mask
Documentation/devicetree/bindings/hwmon/nuvoton,nct6775.example.dtb:0:0: /example-0/i2c/superio@4d: failed to match any schema with compatible: ['nuvoton,nct6779']

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.

Re: [PATCH v4 1/7] dt-bindings: hwmon: Add nuvoton,nct6775

[Krzysztof Kozlowski]

On 27/04/2022 08:44, Zev Weiss wrote:
>>> +  reg:
>>> +    maxItems: 1
>>> +
>>> +  nuvoton,tsi-channel-mask:
>>> +    description:
>>> +      Bitmask indicating which TSI temperature sensor channels are
>>> +      active.  LSB is TSI0, bit 1 is TSI1, etc.
>>
>> Need a type/ref.
>>
> 
> Ack, thanks.

Did you test the bindings after the changes? Using reviewers time
instead of testing by yourself with an automated tool is quite a waste.

Best regards,
Krzysztof

Re: [PATCH v4 1/7] dt-bindings: hwmon: Add nuvoton,nct6775

[Zev Weiss]

On Wed, Apr 27, 2022 at 09:37:20AM PDT, Krzysztof Kozlowski wrote:
>On 27/04/2022 08:44, Zev Weiss wrote:
>>>> +  reg:
>>>> +    maxItems: 1
>>>> +
>>>> +  nuvoton,tsi-channel-mask:
>>>> +    description:
>>>> +      Bitmask indicating which TSI temperature sensor channels are
>>>> +      active.  LSB is TSI0, bit 1 is TSI1, etc.
>>>
>>> Need a type/ref.
>>>
>>
>> Ack, thanks.
>
>Did you test the bindings after the changes? Using reviewers time
>instead of testing by yourself with an automated tool is quite a waste.
>

Yeah, sorry about that -- with uint32 $ref added it passes dt_binding_check;
I'll re-send with that change.


Zev

Re: [PATCH v4 0/7] hwmon: (nct6775) Convert to regmap, add i2c support

[Oleksandr Natalenko]

Hello.

On středa 27. dubna 2022 15:37:07 CEST Guenter Roeck wrote:
> On 4/26/22 18:01, Zev Weiss wrote:
> > This is v4 of my effort to add i2c support to the nct6775 hwmon
> > driver.
> > 
> 
> Thanks a lot for your effort.
> 
> I applied patches 2..6 to hwmon-next. The first and the last
> patch of the series will have to wait for DT maintainer approval.

Zev, sorry I'm late. I've just tested what went into hwmon-next (patches 2..6), and it didn't affect `sensors` output for me, so I guess this confirms what you asked me to do ("I don't have access to any asuswmi hardware, so testing of the nct6775-platform driver on that to ensure it doesn't break there would be appreciated (Oleksandr, perhaps?).").

Guenter, if it's not too late, please consider this as Tested-by: from me on this part of the submission.

Thanks.

-- 
Oleksandr Natalenko (post-factum)

Re: [PATCH v4 0/7] hwmon: (nct6775) Convert to regmap, add i2c support

[Guenter Roeck]

On 5/1/22 08:18, Oleksandr Natalenko wrote:
> Hello.
> 
> On středa 27. dubna 2022 15:37:07 CEST Guenter Roeck wrote:
>> On 4/26/22 18:01, Zev Weiss wrote:
>>> This is v4 of my effort to add i2c support to the nct6775 hwmon
>>> driver.
>>>
>>
>> Thanks a lot for your effort.
>>
>> I applied patches 2..6 to hwmon-next. The first and the last
>> patch of the series will have to wait for DT maintainer approval.
> 
> Zev, sorry I'm late. I've just tested what went into hwmon-next (patches 2..6), and it didn't affect `sensors` output for me, so I guess this confirms what you asked me to do ("I don't have access to any asuswmi hardware, so testing of the nct6775-platform driver on that to ensure it doesn't break there would be appreciated (Oleksandr, perhaps?).").
> 
> Guenter, if it's not too late, please consider this as Tested-by: from me on this part of the submission.
> 

You'll have to provide a formal Tested-by: tag.

Guenter

Re: [PATCH v4 0/7] hwmon: (nct6775) Convert to regmap, add i2c support

[Oleksandr Natalenko]

On středa 27. dubna 2022 15:37:07 CEST Guenter Roeck wrote:
> Hi Zev,
> 
> On 4/26/22 18:01, Zev Weiss wrote:
> > Hello,
> > 
> > This is v4 of my effort to add i2c support to the nct6775 hwmon
> > driver.
> > 
> 
> Thanks a lot for your effort.
> 
> I applied patches 2..6 to hwmon-next. The first and the last
> patch of the series will have to wait for DT maintainer approval.

For patches 2..6:

Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>

> 
> Thanks,
> Guenter
> 


-- 
Oleksandr Natalenko (post-factum)

Re: [PATCH v4 0/7] hwmon: (nct6775) Convert to regmap, add i2c support

[Guenter Roeck]

On 5/1/22 23:06, Oleksandr Natalenko wrote:
> On středa 27. dubna 2022 15:37:07 CEST Guenter Roeck wrote:
>> Hi Zev,
>>
>> On 4/26/22 18:01, Zev Weiss wrote:
>>> Hello,
>>>
>>> This is v4 of my effort to add i2c support to the nct6775 hwmon
>>> driver.
>>>
>>
>> Thanks a lot for your effort.
>>
>> I applied patches 2..6 to hwmon-next. The first and the last
>> patch of the series will have to wait for DT maintainer approval.
> 
> For patches 2..6:
> 
> Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
> 
Thanks, added.

Guenter