Message-ID: <493e4da4-8f2b-9856-b538-6e95e3766d5e@roeck-us.net>
Date:   Thu, 27 May 2021 07:03:10 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Robert Marko <robert.marko@...tura.hr>
Cc:     jdelvare@...e.com, corbet@....net, linux-hwmon@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Luka Perkov <luka.perkov@...tura.hr>, jmp@...phyte.org,
        Paul Menzel <pmenzel@...gen.mpg.de>,
        Donald Buczek <buczek@...gen.mpg.de>
Subject: Re: [PATCH 1/3] hwmon: (pmbus) Add driver for Delta DPS-920AB PSU

On 5/27/21 3:59 AM, Robert Marko wrote:
> On Thu, May 27, 2021 at 12:22 PM Robert Marko <robert.marko@...tura.hr> wrote:
>>
>> On Mon, May 24, 2021 at 3:47 PM Guenter Roeck <linux@...ck-us.net> wrote:
>>>
>>> On 5/24/21 5:21 AM, Robert Marko wrote:
>>>> On Fri, May 21, 2021 at 4:46 PM Guenter Roeck <linux@...ck-us.net> wrote:
>>>>>
>>>>> On 5/21/21 4:56 AM, Robert Marko wrote:
>>>>>> On Fri, May 21, 2021 at 12:56 PM Guenter Roeck <linux@...ck-us.net> wrote:
>>>>>>>
>>>>>>> On 5/21/21 1:36 AM, Robert Marko wrote:
>>>>>>>> On Wed, May 19, 2021 at 3:19 PM Guenter Roeck <linux@...ck-us.net> wrote:
>>>>>>>>>
>>>>>>>>> On 5/19/21 5:38 AM, Robert Marko wrote:
>>>>>>>>>> On Fri, Apr 30, 2021 at 3:48 PM Guenter Roeck <linux@...ck-us.net> wrote:
>>>>>>>>>>>
>>>>>>>>>>> On Fri, Apr 30, 2021 at 03:27:33PM +0200, Robert Marko wrote:
>>>>>>>>>>>> This adds support for the Delta DPS-920AB PSU.
>>>>>>>>>>>>
>>>>>>>>>>>> Only missing feature is fan control which the PSU supports.
>>>>>>>>>>>>
>>>>>>>>>>>> Signed-off-by: Robert Marko <robert.marko@...tura.hr>
>>>>>>>>>>>> ---
>>>>>>>>>>>>       Documentation/hwmon/dps920ab.rst | 80 ++++++++++++++++++++++++++++++++
>>>>>>>>>>>>       Documentation/hwmon/index.rst    |  1 +
>>>>>>>>>>>>       drivers/hwmon/pmbus/Kconfig      |  9 ++++
>>>>>>>>>>>>       drivers/hwmon/pmbus/Makefile     |  1 +
>>>>>>>>>>>>       drivers/hwmon/pmbus/dps920ab.c   | 63 +++++++++++++++++++++++++
>>>>>>>>>>>>       5 files changed, 154 insertions(+)
>>>>>>>>>>>>       create mode 100644 Documentation/hwmon/dps920ab.rst
>>>>>>>>>>>>       create mode 100644 drivers/hwmon/pmbus/dps920ab.c
>>>>>>>>>>>>
>>>>>>>>>>>> diff --git a/Documentation/hwmon/dps920ab.rst b/Documentation/hwmon/dps920ab.rst
>>>>>>>>>>>> new file mode 100644
>>>>>>>>>>>> index 000000000000..df0aef530c7e
>>>>>>>>>>>> --- /dev/null
>>>>>>>>>>>> +++ b/Documentation/hwmon/dps920ab.rst
>>>>>>>>>>>> @@ -0,0 +1,80 @@
>>>>>>>>>>>> +.. SPDX-License-Identifier: GPL-2.0-or-later
>>>>>>>>>>>> +
>>>>>>>>>>>> +Kernel driver dps920ab
>>>>>>>>>>>> +========================
>>>>>>>>>>>> +
>>>>>>>>>>>> +Supported chips:
>>>>>>>>>>>> +
>>>>>>>>>>>> +  * Delta DPS920AB
>>>>>>>>>>>> +
>>>>>>>>>>>> +    Prefix: 'dps920ab'
>>>>>>>>>>>> +
>>>>>>>>>>>> +    Addresses scanned: -
>>>>>>>>>>>> +
>>>>>>>>>>>> +Authors:
>>>>>>>>>>>> +    Robert Marko <robert.marko@...tura.hr>
>>>>>>>>>>>> +
>>>>>>>>>>>> +
>>>>>>>>>>>> +Description
>>>>>>>>>>>> +-----------
>>>>>>>>>>>> +
>>>>>>>>>>>> +This driver implements support for Delta DPS920AB 920W 54V DC single output
>>>>>>>>>>>> +power supply with PMBus support.
>>>>>>>>>>>> +
>>>>>>>>>>>> +The driver is a client driver to the core PMBus driver.
>>>>>>>>>>>> +Please see Documentation/hwmon/pmbus.rst for details on PMBus client drivers.
>>>>>>>>>>>> +
>>>>>>>>>>>> +
>>>>>>>>>>>> +Usage Notes
>>>>>>>>>>>> +-----------
>>>>>>>>>>>> +
>>>>>>>>>>>> +This driver does not auto-detect devices. You will have to instantiate the
>>>>>>>>>>>> +devices explicitly. Please see Documentation/i2c/instantiating-devices.rst for
>>>>>>>>>>>> +details.
>>>>>>>>>>>> +
>>>>>>>>>>>> +
>>>>>>>>>>>> +Sysfs entries
>>>>>>>>>>>> +-------------
>>>>>>>>>>>> +
>>>>>>>>>>>> +======================= ======================================================
>>>>>>>>>>>> +curr1_label          "iin"
>>>>>>>>>>>> +curr1_input          Measured input current
>>>>>>>>>>>> +curr1_crit           Critical maximum current
>>>>>>>>>>>> +curr1_crit_alarm     Current critical high alarm
>>>>>>>>>>>> +
>>>>>>>>>>>> +curr2_label          "iout1"
>>>>>>>>>>>> +curr2_input          Measured output current
>>>>>>>>>>>> +curr2_crit           Critical maximum current
>>>>>>>>>>>> +curr2_crit_alarm     Current critical high alarm
>>>>>>>>>>>> +
>>>>>>>>>>>> +in1_label            "vin"
>>>>>>>>>>>> +in1_input            Measured input voltage
>>>>>>>>>>>> +in1_lcrit            Critical minimum input voltage
>>>>>>>>>>>> +in1_lcrit_alarm              Input voltage critical low alarm
>>>>>>>>>>>> +in1_crit             Critical maximum input voltage
>>>>>>>>>>>> +in1_crit_alarm               Input voltage critical high alarm
>>>>>>>>>>>> +
>>>>>>>>>>>> +in2_label            "vout1"
>>>>>>>>>>>> +in2_input            Measured output voltage
>>>>>>>>>>>> +in2_lcrit            Critical minimum output voltage
>>>>>>>>>>>> +in2_lcrit_alarm              Output voltage critical low alarm
>>>>>>>>>>>> +in2_crit             Critical maximum output voltage
>>>>>>>>>>>> +in2_crit_alarm               Output voltage critical high alarm
>>>>>>>>>>>> +
>>>>>>>>>>>> +power1_label         "pin"
>>>>>>>>>>>> +power1_input         Measured input power
>>>>>>>>>>>> +power1_alarm         Input power high alarm
>>>>>>>>>>>> +
>>>>>>>>>>>> +power2_label         "pout1"
>>>>>>>>>>>> +power2_input         Measured output power
>>>>>>>>>>>> +
>>>>>>>>>>>> +temp[1-2]_input              Measured temperature
>>>>>>>>>>>> +temp[1-2]_crit               Critical high temperature
>>>>>>>>>>>> +temp[1-2]_crit_alarm Chip temperature critical high alarm
>>>>>>>>>>>> +temp[1-2]_max                Maximum temperature
>>>>>>>>>>>> +temp[1-2]_max_alarm  Chip temperature high alarm
>>>>>>>>>>>> +
>>>>>>>>>>>> +fan1_alarm           Fan 1 warning.
>>>>>>>>>>>> +fan1_fault           Fan 1 fault.
>>>>>>>>>>>> +fan1_input           Fan 1 speed in RPM.
>>>>>>>>>>>> +======================= ======================================================
>>>>>>>>>>>> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
>>>>>>>>>>>> index 8d5a2df1ecb6..b24436f22052 100644
>>>>>>>>>>>> --- a/Documentation/hwmon/index.rst
>>>>>>>>>>>> +++ b/Documentation/hwmon/index.rst
>>>>>>>>>>>> @@ -54,6 +54,7 @@ Hardware Monitoring Kernel Drivers
>>>>>>>>>>>>          dell-smm-hwmon
>>>>>>>>>>>>          dme1737
>>>>>>>>>>>>          drivetemp
>>>>>>>>>>>> +   dps920ab
>>>>>>>>>>>>          ds1621
>>>>>>>>>>>>          ds620
>>>>>>>>>>>>          emc1403
>>>>>>>>>>>> diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
>>>>>>>>>>>> index 32d2fc850621..865ade0aa205 100644
>>>>>>>>>>>> --- a/drivers/hwmon/pmbus/Kconfig
>>>>>>>>>>>> +++ b/drivers/hwmon/pmbus/Kconfig
>>>>>>>>>>>> @@ -66,6 +66,15 @@ config SENSORS_IBM_CFFPS
>>>>>>>>>>>>              This driver can also be built as a module. If so, the module will
>>>>>>>>>>>>              be called ibm-cffps.
>>>>>>>>>>>>
>>>>>>>>>>>> +config SENSORS_DPS920AB
>>>>>>>>>>>> +     tristate "Delta DPS920AB Power Supply"
>>>>>>>>>>>> +     help
>>>>>>>>>>>> +       If you say yes here you get hardware monitoring support for Delta
>>>>>>>>>>>> +       DPS920AB Power Supplies.
>>>>>>>>>>>> +
>>>>>>>>>>>> +       This driver can also be built as a module. If so, the module will
>>>>>>>>>>>> +       be called dps920ab.
>>>>>>>>>>>> +
>>>>>>>>>>>>       config SENSORS_INSPUR_IPSPS
>>>>>>>>>>>>            tristate "INSPUR Power System Power Supply"
>>>>>>>>>>>>            help
>>>>>>>>>>>> diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
>>>>>>>>>>>> index 6a4ba0fdc1db..f59ba0123d68 100644
>>>>>>>>>>>> --- a/drivers/hwmon/pmbus/Makefile
>>>>>>>>>>>> +++ b/drivers/hwmon/pmbus/Makefile
>>>>>>>>>>>> @@ -9,6 +9,7 @@ obj-$(CONFIG_SENSORS_ADM1266) += adm1266.o
>>>>>>>>>>>>       obj-$(CONFIG_SENSORS_ADM1275)        += adm1275.o
>>>>>>>>>>>>       obj-$(CONFIG_SENSORS_BEL_PFE)        += bel-pfe.o
>>>>>>>>>>>>       obj-$(CONFIG_SENSORS_IBM_CFFPS)      += ibm-cffps.o
>>>>>>>>>>>> +obj-$(CONFIG_SENSORS_DPS920AB)       += dps920ab.o
>>>>>>>>>>>>       obj-$(CONFIG_SENSORS_INSPUR_IPSPS) += inspur-ipsps.o
>>>>>>>>>>>>       obj-$(CONFIG_SENSORS_IR35221)        += ir35221.o
>>>>>>>>>>>>       obj-$(CONFIG_SENSORS_IR38064)        += ir38064.o
>>>>>>>>>>>> diff --git a/drivers/hwmon/pmbus/dps920ab.c b/drivers/hwmon/pmbus/dps920ab.c
>>>>>>>>>>>> new file mode 100644
>>>>>>>>>>>> index 000000000000..d579ed9f879c
>>>>>>>>>>>> --- /dev/null
>>>>>>>>>>>> +++ b/drivers/hwmon/pmbus/dps920ab.c
>>>>>>>>>>>> @@ -0,0 +1,63 @@
>>>>>>>>>>>> +// SPDX-License-Identifier: GPL-2.0-or-later
>>>>>>>>>>>> +/*
>>>>>>>>>>>> + * Driver for Delta DPS920AB PSU
>>>>>>>>>>>> + *
>>>>>>>>>>>> + * Copyright (C) 2021 Delta Networks, Inc.
>>>>>>>>>>>> + * Copyright (C) 2021 Sartura Ltd.
>>>>>>>>>>>> + */
>>>>>>>>>>>> +
>>>>>>>>>>>> +#include <linux/i2c.h>
>>>>>>>>>>>> +#include <linux/module.h>
>>>>>>>>>>>> +#include <linux/of_device.h>
>>>>>>>>>>>> +#include "pmbus.h"
>>>>>>>>>>>> +
>>>>>>>>>>>> +static struct pmbus_driver_info dps920ab_info = {
>>>>>>>>>>>> +     .pages = 1,
>>>>>>>>>>>> +
>>>>>>>>>>>> +     .format[PSC_VOLTAGE_IN] = linear,
>>>>>>>>>>>> +     .format[PSC_VOLTAGE_OUT] = linear,
>>>>>>>>>>>> +     .format[PSC_CURRENT_IN] = linear,
>>>>>>>>>>>> +     .format[PSC_CURRENT_OUT] = linear,
>>>>>>>>>>>> +     .format[PSC_POWER] = linear,
>>>>>>>>>>>> +     .format[PSC_FAN] = linear,
>>>>>>>>>>>> +     .format[PSC_TEMPERATURE] = linear,
>>>>>>>>>>>> +
>>>>>>>>>>>> +     .func[0] = PMBUS_HAVE_VIN | PMBUS_HAVE_IIN  |
>>>>>>>>>>>> +     PMBUS_HAVE_VOUT  | PMBUS_HAVE_STATUS_VOUT   |
>>>>>>>>>>>> +     PMBUS_HAVE_IOUT  | PMBUS_HAVE_STATUS_IOUT   |
>>>>>>>>>>>> +     PMBUS_HAVE_TEMP  | PMBUS_HAVE_TEMP2         |
>>>>>>>>>>>> +     PMBUS_HAVE_PIN   | PMBUS_HAVE_POUT          |
>>>>>>>>>>>> +     PMBUS_HAVE_FAN12 | PMBUS_HAVE_STATUS_FAN12  |
>>>>>>>>>>>> +     PMBUS_HAVE_STATUS_INPUT | PMBUS_HAVE_STATUS_TEMP,
>>>>>>>>>>>> +};
>>>>>>>>>>>> +
>>>>>>>>>>>> +static int dps920ab_probe(struct i2c_client *client)
>>>>>>>>>>>> +{
>>>>>>>>>>>> +     if (!i2c_check_functionality(client->adapter,
>>>>>>>>>>>> +                                  I2C_FUNC_SMBUS_BYTE_DATA |
>>>>>>>>>>>> +                                  I2C_FUNC_SMBUS_WORD_DATA))
>>>>>>>>>>>> +             return -ENODEV;
>>>>>>>>>>>
>>>>>>>>>>> This check is done in pmbus_do_probe(), and repeating it here does not add
>>>>>>>>>>> any value.
>>>>>>>>>>
>>>>>>>>>> Ok, makes sense.
>>>>>>>>>>>
>>>>>>>>>>> That makes me wonder: Is this driver needed in the first place, or could
>>>>>>>>>>> it be added to drivers/hwmon/pmbus/pmbus.c ?
>>>>>>>>>>
>>>>>>>>>> It could be added as a generic driver, but that creates properties in
>>>>>>>>>> the sysfs that this thing
>>>>>>>>>> does not support like 3 voltage readings, 3 fans, and so on.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Can you be more specific ? What additional unsupported attributes
>>>>>>>>> are added, and why ? Are you saying the PSU reports registers as
>>>>>>>>> existing which do not really exist ? If so, which registers are those ?
>>>>>>>>
>>>>>>>> Sure, when core does probing and autodiscovery, then the following
>>>>>>>> sysfs attributes are created:
>>>>>>>>>
>>>>>>>>> curr1_crit         fan3_fault       in3_min_alarm      temp1_max
>>>>>>>>> curr1_crit_alarm   fan3_input       in3_rated_max      temp1_max_alarm
>>>>>>>>> curr1_input        fan3_target      in3_rated_min      temp1_min
>>>>>>>>> curr1_label        in1_crit         name               temp1_min_alarm
>>>>>>>>> curr1_max          in1_crit_alarm   of_node            temp1_rated_max
>>>>>>>>> curr1_max_alarm    in1_input        power              temp2_crit
>>>>>>>>> curr1_rated_max    in1_label        power1_alarm       temp2_crit_alarm
>>>>>>>>> curr2_crit         in1_lcrit        power1_input       temp2_input
>>>>>>>>> curr2_crit_alarm   in1_lcrit_alarm  power1_label       temp2_lcrit
>>>>>>>>> curr2_input        in1_max          power1_max         temp2_lcrit_alarm
>>>>>>>>> curr2_label        in1_max_alarm    power1_rated_max   temp2_max
>>>>>>>>> curr2_lcrit        in1_min          power2_cap         temp2_max_alarm
>>>>>>>>> curr2_lcrit_alarm  in1_min_alarm    power2_cap_alarm   temp2_min
>>>>>>>>> curr2_max          in1_rated_max    power2_crit        temp2_min_alarm
>>>>>>>>> curr2_max_alarm    in1_rated_min    power2_crit_alarm  temp2_rated_max
>>>>>>>>> curr2_rated_max    in2_input        power2_input       temp3_crit
>>>>>>>>> device             in2_label        power2_label       temp3_crit_alarm
>>>>>>>>> fan1_alarm         in3_crit         power2_max         temp3_input
>>>>>>>>> fan1_fault         in3_crit_alarm   power2_max_alarm   temp3_lcrit
>>>>>>>>> fan1_input         in3_input        power2_rated_max   temp3_lcrit_alarm
>>>>>>>>> fan1_target        in3_label        subsystem          temp3_max
>>>>>>>>> fan2_alarm         in3_lcrit        temp1_crit         temp3_max_alarm
>>>>>>>>> fan2_fault         in3_lcrit_alarm  temp1_crit_alarm   temp3_min
>>>>>>>>> fan2_input         in3_max          temp1_input        temp3_min_alarm
>>>>>>>>> fan2_target        in3_max_alarm    temp1_lcrit        temp3_rated_max
>>>>>>>>> fan3_alarm         in3_min          temp1_lcrit_alarm  uevent
>>>>>>>>
>>>>>>>> The following return -1, or -500 so they are not supported.
>>>>>>>> * fan2
>>>>>>>> * in2
>>>>>>>>
>>>>>>>> Weirdly, with the external driver both fan2 and in2 are enabled and work fine,
>>>>>>>> but when auto probing they are fan3 and in3.
>>>>>>>>
>>>>>>>> temp3 actually seems to return a valid temperature despite it not being used in
>>>>>>>> the vendor driver that features were picked from.
>>>>>>>>
>>>>>>>
>>>>>>> Can you run "grep . *" in the hwmon directory so I can see actual values ?
>>>>>>>
>>>>>> Sure:
>>>>>>>
>>>>>>> curr1_crit:-500
>>>>>>> curr1_crit_alarm:0
>>>>>>> curr1_input:195
>>>>>>> curr1_label:iin
>>>>>>> curr1_max:-500
>>>>>>> curr1_max_alarm:0
>>>>>>> curr1_rated_max:-500
>>>>>>> curr2_crit:-500
>>>>>>> curr2_crit_alarm:0
>>>>>>> curr2_input:320
>>>>>>> curr2_label:iout1
>>>>>>> curr2_lcrit:-500
>>>>>>> curr2_lcrit_alarm:0
>>>>>>> curr2_max:18625
>>>>>>> curr2_max_alarm:0
>>>>>>> curr2_rated_max:16875
>>>>>>> grep: device: Is a directory
>>>>>>> fan1_alarm:0
>>>>>>> fan1_fault:0
>>>>>>> fan1_input:10000
>>>>>>> fan1_target:0
>>>>>>> fan2_alarm:1
>>>>>>> fan2_fault:1
>>>>>>> fan2_input:-1
>>>>>>> fan2_target:-1
>>>>>>> fan3_alarm:1
>>>>>>> fan3_fault:1
>>>>>>> fan3_input:-1
>>>>>>> fan3_target:-1
>>>>>>> in1_crit:-500
>>>>>>> in1_crit_alarm:0
>>>>>>> in1_input:245250
>>>>>>> in1_label:vin
>>>>>>> in1_lcrit:-500
>>>>>>> in1_lcrit_alarm:0
>>>>>>> in1_max:-500
>>>>>>> in1_max_alarm:0
>>>>>>> in1_min:-500
>>>>>>> in1_min_alarm:0
>>>>>>> in1_rated_max:-500
>>>>>>> in1_rated_min:-500
>>>>>>> in2_input:-500
>>>>>>> in2_label:vcap
>>>>>>> in3_crit:255996
>>>>>>> in3_crit_alarm:0
>>>>>>> in3_input:54511
>>>>>>> in3_label:vout1
>>>>>>> in3_lcrit:255996
>>>>>>> in3_lcrit_alarm:0
>>>>>>> in3_max:255996
>>>>>>> in3_max_alarm:0
>>>>>>> in3_min:255996
>>>>>>> in3_min_alarm:0
>>>>>>> in3_rated_max:56136
>>>>>>> in3_rated_min:52863
>>>>>>> name:dps920ab
>>>>>>> grep: of_node: Is a directory
>>>>>>> grep: power: Is a directory
>>>>>>> power1_alarm:0
>>>>>>> power1_input:33250000
>>>>>>> power1_label:pin
>>>>>>> power1_max:-500000
>>>>>>> power1_rated_max:-500000
>>>>>>> power2_cap:-500000
>>>>>>> power2_cap_alarm:0
>>>>>>> power2_crit:-500000
>>>>>>> power2_crit_alarm:0
>>>>>>> power2_input:17750000
>>>>>>> power2_label:pout1
>>>>>>> power2_max:-500000
>>>>>>> power2_max_alarm:0
>>>>>>> power2_rated_max:920000000
>>>>>>> grep: subsystem: Is a directory
>>>>>>> temp1_crit:-500
>>>>>>> temp1_crit_alarm:0
>>>>>>> temp1_input:23000
>>>>>>> temp1_lcrit:-500
>>>>>>> temp1_lcrit_alarm:0
>>>>>>> temp1_max:-500
>>>>>>> temp1_max_alarm:0
>>>>>>> temp1_min:-500
>>>>>>> temp1_min_alarm:0
>>>>>>> temp1_rated_max:-500
>>>>>>> temp2_crit:-500
>>>>>>> temp2_crit_alarm:0
>>>>>>> temp2_input:26000
>>>>>>> temp2_lcrit:-500
>>>>>>> temp2_lcrit_alarm:0
>>>>>>> temp2_max:-500
>>>>>>> temp2_max_alarm:0
>>>>>>> temp2_min:-500
>>>>>>> temp2_min_alarm:0
>>>>>>> temp2_rated_max:-500
>>>>>>> temp3_crit:-500
>>>>>>> temp3_crit_alarm:0
>>>>>>> temp3_input:30000
>>>>>>> temp3_lcrit:-500
>>>>>>> temp3_lcrit_alarm:0
>>>>>>> temp3_max:-500
>>>>>>> temp3_max_alarm:0
>>>>>>> temp3_min:-500
>>>>>>> temp3_min_alarm:0
>>>>>>> temp3_rated_max:-500
>>>>>>> uevent:OF_NAME=psu
>>>>>>> uevent:OF_FULLNAME=/ap806/config-space@...00000/i2c@...000/psu@5a
>>>>>>> uevent:OF_COMPATIBLE_0=delta,dps920ab
>>>>>>> uevent:OF_COMPATIBLE_N=1
>>>>>>
>>>>> Ok, good enough. It looks like the PSU reports values for pretty much everything,
>>>>> including registers which don't exist. With that in mind, please check
>>>>> the attributes generated by your driver - I suspect that some of the limit
>>>>> attributes are not really supported (maybe none of them is supported).
>>>>
>>>> Yeah, I also think that none of those limits are actually supported.
>>>> Does the core expose a way to not register those?
>>>>
>>>
>>> Have the read_word function return -ENXIO for unsupported registers
>>> (and add a comment to the code explaining why you do that).
>>> See drivers/hwmon/pmbus/fsp-3y.c for an example.
>>
>> Thanks, will implement that.
>> In the meantime I finally got the PMBus command list that
>> the PSU supports.
>> It implements PMBus 1.2, but it also claims that MFR_ID,
>> MFR_MODEL and MFR_REVISION are supported.
>>
>> Block read returns what looks like a correct length, but the buffer
>> is empty.
>>>
>>> [  195.246464] dps920ab 0-005a: PMBUS_MFR_ID length: 5
>>> [  195.251495] dps920ab 0-005a: PMBUS_MFR_ID:
>>> [  195.300789] dps920ab 0-005b: PMBUS_MFR_ID length: 5
>>> [  195.305762] dps920ab 0-005b: PMBUS_MFR_ID:
>>> [  272.795222] dps920ab 0-005a: PMBUS_MFR_ID length: 5
>>> [  272.800190] dps920ab 0-005a: PMBUS_MFR_ID:
>>> [  272.804862] dps920ab 0-005a: PMBUS_MFR_MODEL length: 11
>>> [  272.810172] dps920ab 0-005a: PMBUS_MFR_MODEL:
>>> [  272.815098] dps920ab 0-005a: PMBUS_MFR_REVISION length: 2
>>> [  272.820600] dps920ab 0-005a: PMBUS_MFR_REVISION:
>>> [  272.874060] dps920ab 0-005b: PMBUS_MFR_ID length: 5
>>> [  272.879102] dps920ab 0-005b: PMBUS_MFR_ID:
>>> [  272.883833] dps920ab 0-005b: PMBUS_MFR_MODEL length: 11
>>> [  272.889151] dps920ab 0-005b: PMBUS_MFR_MODEL:
>>> [  272.894097] dps920ab 0-005b: PMBUS_MFR_REVISION length: 2
>>> [  272.899548] dps920ab 0-005b: PMBUS_MFR_REVISION:
>>
>>
>> However, manually reading using i2cget in word mode returns
>> something that looks ok.
>> i2cget -y 0 0x5a 0x9a w
>> 0x440b
>>
>> This would be D is ASCII, it looks like any kind of block read fails actually.
> 
> Ok, so after using i2c_smbus_read_i2c_block_data() I can actually read
> the model kind of OK.
> There actually are 10 bytes of valid data, no idea why
> i2c_smbus_read_block_data() does not work.
>>
>> [  721.194706] dps920ab 0-005a: MFR MODEL:
>>                                             DPS-920AB
>> [  721.245502] dps920ab 0-005b: MFR MODEL:
>>                                             DPS-920AB
> 
> It behaves weirdly when printing by creating a newline before and
> stuff like that.
> 

I suspect it prints the first byte, which should be the length.
I also suspect that the i2c controller driver has a bug and doesn't
support SMBus block data correctly. Did you try i2cdump with i and s
options ?

>> I tried applying the block support for mv64xx as well:
>> https://patchwork.ozlabs.org/project/linux-i2c/patch/20200118115820.9080-1-fuga@studiofuga.com/

That patch would be needed, but it looks buggy to me. This chunk:

+		drv_data->effective_length = data+1;
+		drv_data->bytes_left = data+1;
+		drv_data->msg->len = data+1;

should be:

+		drv_data->effective_length = data+1;
+		drv_data->bytes_left = data;
+		drv_data->msg->len = data+1;

It should also make sure that 'data' is not larger than I2C_SMBUS_BLOCK_MAX,
and bail out if it isn't.

Do you see a difference with the patch applied ?

Guenter

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