Re: [PATCH 2/2] hwmon: pmbus: adm1275: add adm1281 support

From: Guenter Roeck
Date: Wed Apr 17 2024 - 11:25:17 EST


On Tue, Apr 16, 2024 at 05:32:46PM -0700, Guenter Roeck wrote:
> On Wed, Apr 17, 2024 at 08:07:22AM +0800, Jose Ramon San Buenaventura wrote:
> > Adding support for adm1281 which is similar to adm1275
> >
> > ADM1281 has STATUS_CML read support which is also being added.
> >
> > Signed-off-by: Jose Ramon San Buenaventura <jose.sanbuenaventura@xxxxxxxxxx>
> > ---
> > Documentation/hwmon/adm1275.rst | 14 +++++++++++---
> > drivers/hwmon/pmbus/Kconfig | 4 ++--
> > drivers/hwmon/pmbus/adm1275.c | 27 +++++++++++++++++++++++++--
> > 3 files changed, 38 insertions(+), 7 deletions(-)
> >
> > diff --git a/Documentation/hwmon/adm1275.rst b/Documentation/hwmon/adm1275.rst
> > index 804590eea..467daf8ce 100644
> > --- a/Documentation/hwmon/adm1275.rst
> > +++ b/Documentation/hwmon/adm1275.rst
> > @@ -43,6 +43,14 @@ Supported chips:
> >
> > Datasheet: www.analog.com/static/imported-files/data_sheets/ADM1278.pdf
> >
> > + * Analog Devices ADM1281
> > +
> > + Prefix: 'adm1281'
> > +
> > + Addresses scanned: -
> > +
> > + Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/adm1281.pdf
> > +
> > * Analog Devices ADM1293/ADM1294
> >
> > Prefix: 'adm1293', 'adm1294'
> > @@ -58,10 +66,10 @@ Description
> > -----------
> >
> > This driver supports hardware monitoring for Analog Devices ADM1075, ADM1272,
> > -ADM1275, ADM1276, ADM1278, ADM1293, and ADM1294 Hot-Swap Controller and
> > +ADM1275, ADM1276, ADM1278, ADM1281, ADM1293, and ADM1294 Hot-Swap Controller and
> > Digital Power Monitors.
> >
> > -ADM1075, ADM1272, ADM1275, ADM1276, ADM1278, ADM1293, and ADM1294 are hot-swap
> > +ADM1075, ADM1272, ADM1275, ADM1276, ADM1278, ADM1281, ADM1293, and ADM1294 are hot-swap
> > controllers that allow a circuit board to be removed from or inserted into
> > a live backplane. They also feature current and voltage readback via an
> > integrated 12 bit analog-to-digital converter (ADC), accessed using a
> > @@ -144,5 +152,5 @@ temp1_highest Highest observed temperature.
> > temp1_reset_history Write any value to reset history.
> >
> > Temperature attributes are supported on ADM1272 and
> > - ADM1278.
> > + ADM1278, and ADM1281.
> > ======================= =======================================================
> > diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
> > index 557ae0c41..9c1d0d7d5 100644
> > --- a/drivers/hwmon/pmbus/Kconfig
> > +++ b/drivers/hwmon/pmbus/Kconfig
> > @@ -51,8 +51,8 @@ config SENSORS_ADM1275
> > tristate "Analog Devices ADM1275 and compatibles"
> > help
> > If you say yes here you get hardware monitoring support for Analog
> > - Devices ADM1075, ADM1272, ADM1275, ADM1276, ADM1278, ADM1293,
> > - and ADM1294 Hot-Swap Controller and Digital Power Monitors.
> > + Devices ADM1075, ADM1272, ADM1275, ADM1276, ADM1278, ADM1281,
> > + ADM1293, and ADM1294 Hot-Swap Controller and Digital Power Monitors.
> >
> > This driver can also be built as a module. If so, the module will
> > be called adm1275.
> > diff --git a/drivers/hwmon/pmbus/adm1275.c b/drivers/hwmon/pmbus/adm1275.c
> > index e2c61d6fa..6c3e8840f 100644
> > --- a/drivers/hwmon/pmbus/adm1275.c
> > +++ b/drivers/hwmon/pmbus/adm1275.c
> > @@ -18,7 +18,7 @@
> > #include <linux/log2.h>
> > #include "pmbus.h"
> >
> > -enum chips { adm1075, adm1272, adm1275, adm1276, adm1278, adm1293, adm1294 };
> > +enum chips { adm1075, adm1272, adm1275, adm1276, adm1278, adm1281, adm1293, adm1294 };
> >
> > #define ADM1275_MFR_STATUS_IOUT_WARN2 BIT(0)
> > #define ADM1293_MFR_STATUS_VAUX_UV_WARN BIT(5)
> > @@ -101,6 +101,7 @@ struct adm1275_data {
> > bool have_pin_max;
> > bool have_temp_max;
> > bool have_power_sampling;
> > + bool have_status_cml;
> > struct pmbus_driver_info info;
> > };
> >
> > @@ -469,6 +470,22 @@ static int adm1275_read_byte_data(struct i2c_client *client, int page, int reg)
> > ret |= PB_VOLTAGE_UV_WARNING;
> > }
> > break;
> > + case PMBUS_STATUS_CML:
> > + if (!data->have_status_cml)
> > + return -ENXIO;
> > +
> > + ret = pmbus_read_byte_data(client, page, PMBUS_STATUS_BYTE);
> > + if (ret < 0)
> > + break;
>
> You'll have to explain why this additional status byte read
> is necessary (while it isn't necessary for all other chips supporting
> PMBUS_STATUS_CML).
>

After looking more into the existing PMBus code and into this patch,
I really fail to understand why the above change would be needed.
The PMBus core code already reads the status register to check if
there is a communication error. I fail to see why it would be necessary
to do it again, and why it would be necessary to change behavior for
the other chips supported by this driver.

Guenter