Re: [PATCH v2 2/3] hwmon (xdpe12284): Add support for xdpe11280

[Guenter Roeck]

On 2/17/22 08:39, sylv wrote:
> On Thu, 2022-02-17 at 07:20 -0800, Guenter Roeck wrote:
> > On 2/17/22 06:41, Marcello Sylvester Bauer wrote:
> > > Add support for another family of Infineon Multi-phase controllers.
> > > The xdpe11280 uses linear instead of vid data format for VOUT.
> > > Add the required logic to detect VOUT_MODE during identification,
> > > and set the format accordingly.
> > This talks about the chip, but ...
>
> Oh, sure. I should be more clear that it is a chip of a different
> family.
>
> > > Signed-off-by: Marcello Sylvester Bauer <sylv@xxxxxxx>
> > > ---
> > >    Documentation/hwmon/xdpe12284.rst | 10 +++++++---
> > >    drivers/hwmon/pmbus/xdpe12284.c   | 17 ++++++++++++++++-
> > >    2 files changed, 23 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/Documentation/hwmon/xdpe12284.rst
> > > b/Documentation/hwmon/xdpe12284.rst
> > > index 67d1f87808e5..e9a5a19b0c3d 100644
> > > --- a/Documentation/hwmon/xdpe12284.rst
> > > +++ b/Documentation/hwmon/xdpe12284.rst
> > > @@ -5,6 +5,10 @@ Kernel driver xdpe122
> > >    
> > >    Supported chips:
> > >    
> > > +  * Infineon XDPE11280
> > > +
> > > +    Prefix: 'xdpe11280'
> > > +
> > >      * Infineon XDPE12254
> > >    
> > >        Prefix: 'xdpe12254'
> > > @@ -20,9 +24,9 @@ Authors:
> > >    Description
> > >    -----------
> > >    
> > > -This driver implements support for Infineon Multi-phase XDPE122
> > > family
> > > -dual loop voltage regulators.
> > > -The family includes XDPE12284 and XDPE12254 devices.
> > > +This driver implements support for Infineon Multi-phase XDPE112
> > > and XDPE122
> > > +family dual loop voltage regulators.
> > > +These families include XDPE11280, XDPE12284 and XDPE12254 devices.
> > >    The devices from this family complaint with:
> >
> > Hmm, s/complaint/compliant/.
>
> ack
>
> > Anyway, is it still correct that the XDPE11280 is compliant with the
> > Intel specifications ? The datasheet isn't public, so I can not check
> > myself
> > what the chip actually supports.
>
> The hardware we are testing on is an Intel Cascade Lake, which uses
> this chip. The datasheet tells us it is compliant:
>
> ```
> The XDPE11280B implements a fully compliant Intel® VR 13, VR12, VR
> 12.5, VR13.HC, and IMVP8 Serial VID (SVID)
> interface.
> ```

This seems to be one of those chips where the vendor doesn't even admit
that it exists unless one signs an NDA. Sigh :-(.

> > >    
> > >    - Intel VR13 and VR13HC rev 1.3, IMVP8 rev 1.2 and IMPVP9 rev 1.3
> > > DC-DC
> > > diff --git a/drivers/hwmon/pmbus/xdpe12284.c
> > > b/drivers/hwmon/pmbus/xdpe12284.c
> > > index b07da06a40c9..ec947c697670 100644
> > > --- a/drivers/hwmon/pmbus/xdpe12284.c
> > > +++ b/drivers/hwmon/pmbus/xdpe12284.c
> > > @@ -27,6 +27,9 @@ static int xdpe122_read_word_data(struct
> > > i2c_client *client, int page,
> > >          s32 mantissa;
> > >          int ret;
> > >    
> > > +       if (info->format[PSC_VOLTAGE_OUT] == linear)
> > > +               return -ENODATA;
> > > +
> > >          switch (reg) {
> > >          case PMBUS_VOUT_OV_FAULT_LIMIT:
> > >          case PMBUS_VOUT_UV_FAULT_LIMIT:
> > > @@ -75,9 +78,19 @@ static int xdpe122_read_word_data(struct
> > > i2c_client *client, int page,
> > >    static int xdpe122_identify(struct i2c_client *client,
> > >                              struct pmbus_driver_info *info)
> > >    {
> > > -       u8 vout_params;
> > > +       u8 vout_mode, vout_params;
> > >          int i, ret;
> > >    
> > > +       ret = pmbus_read_byte_data(client, 0, PMBUS_VOUT_MODE);
> > > +       if (ret < 0)
> > > +               return ret;
> > > +
> > > +       vout_mode = ret >> 5;
> > > +       if (vout_mode == 0) {
> > > +               info->format[PSC_VOLTAGE_OUT] = linear;
> > > +               return 0;
> > > +       }
> >
> > .... the code above is not chip dependent but this code checks the
> > mode register on page 0. At the very least this is confusing.
> >
> > What the driver should do instead is to check the chip type during
> > probe and make the necessary changes there, ie set the output format
> > for xdpe11280 to linear and drop the pointers to the .identify
> > and .read_word_data.
>
> Sgtm. This sounds like a better approach indeed.

That makes me wonder if the chip needs to be added to this driver in the first
place, or if it could be added to pmbus.c instead. Any idea ?

Thanks,
Guenter

> Thanks,
> Marcello
>
> > Guenter
> >
> > > +
> > >          for (i = 0; i < XDPE122_PAGE_NUM; i++) {
> > >                  /* Read the register with VOUT scaling value.*/
> > >                  ret = pmbus_read_byte_data(client, i,
> > > PMBUS_VOUT_MODE);
> > > @@ -140,6 +153,7 @@ static int xdpe122_probe(struct i2c_client
> > > *client)
> > >    }
> > >    
> > >    static const struct i2c_device_id xdpe122_id[] = {
> > > +       {"xdpe11280", 0},
> > >          {"xdpe12254", 0},
> > >          {"xdpe12284", 0},
> > >          {}
> > > @@ -148,6 +162,7 @@ static const struct i2c_device_id xdpe122_id[]
> > > = {
> > >    MODULE_DEVICE_TABLE(i2c, xdpe122_id);
> > >    
> > >    static const struct of_device_id __maybe_unused
> > > xdpe122_of_match[] = {
> > > +       {.compatible = "infineon,xdpe11280"},
> > >          {.compatible = "infineon,xdpe12254"},
> > >          {.compatible = "infineon,xdpe12284"},
> > >          {}