Re: [PATCH v3] hwmon: Add driver for the TEXAS TPS546D24 Buck Converter.

[Duke Du]

Hi Guenter,
Thanks for your reply !
But I have some confusion as following, please help to give me some feedback.
Thanks a lot !

On Fri, Aug 19, 2022 at 9:35 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>
> On Fri, Aug 19, 2022 at 11:04:43AM +0800, Duke Du wrote:
> > Add the pmbus driver for TEXAS tps546d24 Buck Converter. The
> > tps546d24 PMBUS_VOUT_MODE is 0x97 (i.e. the bit 5~7 are 100)
> > which could not meet the standard pmbus spec, the standard mode
> > of PMBUS_VOUT_MODE must be 000 (linear foramt) or 001 (vid format).
> > Make the tps546d24 PMBUS_VOUT_MODE return value 0x17 (i.e. the
> > bit5~7 are 000), VOUT returned value is linear11.
> >
>
> First of all, the above should be documented as comment in the
> implementation.
>
> Second, this is actually problematic. In PMBus version 1.3.1, bit
> 7 of PMBUS_VOUT_MODE no longer describes the mode (linear, vid, direct,
> IEEE) but Absolute vs/ Relative VOUT voltages. This affects vout fault
> and warning limits. If the relative mode bit is set, those limits
> are supposed to reflect percentages, not absolute voltages.
>
> This means that the driver interprets vout voltage limits wrongly,
> at least if the chip works as described in the datasheet. Changing
> the reported value of PMBUS_VOUT_MODE is actually counter-productive.
>
> This means we'll need a number of changes. At the very least, the
> PMBus core needs to be be modified to only use bit 5 and 6 to determine
> the mode. On top of that, the driver probe function should update
> VOUT_MODE and clear bit 7. It might also make sense to warn in the
> PMBus core if mode bit 7 is set.
>

When the vout mode bit 7 is set, we update vout mode and clear bit 7
in the driver probe function, this operation is the same as changing
the reported value of PMBUS_VOUT_MODE ?
Maybe I misunderstood, could you please help to explain clearly about this ?
Thanks again for your help :)

Thanks,
Duke

> An alternative to the second change would be to implement relative
> vout support in the PMBus core, but that would be much more complex.
> We could also clear the relative bit in the PMBus core, but that might
> lead to unexpected side effects (we don't know how various chips
> respond to that) and thus probably not be a good idea.
>
> > Signed-off-by: Duke Du <Duke.Du@xxxxxxxxxxxx>
>
> This e-mail address does not match the e-mail address used to send
> the patch, resulting in a checkpatch warning. Please fix.
>
> More comments inline.
>
> Thanks,
> Guenter
>
> > ---
> > Change in v1:
> >     Initial patchset.
> > Change in v2:
> >     Correct the tps546d24.rst format.
> > Change in v3:
> >     1. Modify the patch description.
> >     2. Put the change log between the dashes and diffstat.
> > ---
> > ---
> >  Documentation/hwmon/index.rst     |  1 +
> >  Documentation/hwmon/tps546d24.rst | 35 +++++++++++++++++++
> >  MAINTAINERS                       |  7 ++++
> >  drivers/hwmon/pmbus/Kconfig       |  9 +++++
> >  drivers/hwmon/pmbus/Makefile      |  1 +
> >  drivers/hwmon/pmbus/tps546d24.c   | 73 +++++++++++++++++++++++++++++++++++++++
> >  6 files changed, 126 insertions(+)
> >  create mode 100644 Documentation/hwmon/tps546d24.rst
> >  create mode 100644 drivers/hwmon/pmbus/tps546d24.c
> >
> > diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> > index f7113b0..d3eede4 100644
> > --- a/Documentation/hwmon/index.rst
> > +++ b/Documentation/hwmon/index.rst
> > @@ -205,6 +205,7 @@ Hardware Monitoring Kernel Drivers
> >     tps23861
> >     tps40422
> >     tps53679
> > +   tps546d24
> >     twl4030-madc-hwmon
> >     ucd9000
> >     ucd9200
> > diff --git a/Documentation/hwmon/tps546d24.rst b/Documentation/hwmon/tps546d24.rst
> > new file mode 100644
> > index 0000000..3061fd8
> > --- /dev/null
> > +++ b/Documentation/hwmon/tps546d24.rst
> > @@ -0,0 +1,35 @@
> > +.. SPDX-License-Identifier: GPL-2.0-only
> > +
> > +Kernel driver tps546d24
> > +======================
> > +
> > +Supported chips:
> > +
> > +  * TI TPS546D24
> > +
> > +    Prefix: 'tps546d24'
> > +
> > +    Addresses scanned: -
> > +
> > +    Datasheet: https://www.ti.com/lit/gpn/tps546d24
> > +
> > +Author: Duke Du <dukedu83@xxxxxxxxx>
>
> This needs to match Author and Signed-off-by:. This applies to all
> e-mail addresses.
>
> > +
> > +
> > +Description
> > +-----------
> > +
> > +The TPS546D24A is a highly integrated, non-isolated DC/DC converter capable
> > +of high frequency operation and 40-A current output from a 7-mm x 5-mm
> > +package.
> > +
> > +Two, three, and four TPS546D24A devices can be interconnected
> > +to provide up to 160 A on a single output. The device has an option to
> > +overdrive the internal 5-V LDO with an external 5-V supply via the VDD5
> > +pin to improve efficiency and reduce power dissipation of the converter.
> > +
> > +
> > +Platform data support
> > +---------------------
> > +
> > +The driver supports standard PMBus driver platform data.
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 8a5012b..fa2d4fb 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -20583,6 +20583,13 @@ Q:   https://patchwork.kernel.org/project/linux-integrity/list/
> >  T:   git git://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd.git
> >  F:   drivers/char/tpm/
> >
> > +TPS546D24 DRIVER
> > +M:   Duke Du <dukedu83@xxxxxxxxx>
> > +L:   linux-hwmon@xxxxxxxxxxxxxxx
> > +S:   Maintained
> > +F:   Documentation/hwmon/tps546d24.rst
> > +F:   drivers/hwmon/pmbus/tps546d24.c
> > +
> >  TRACING
> >  M:   Steven Rostedt <rostedt@xxxxxxxxxxx>
> >  M:   Ingo Molnar <mingo@xxxxxxxxxx>
> > diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
> > index 951e4a9..89668af 100644
> > --- a/drivers/hwmon/pmbus/Kconfig
> > +++ b/drivers/hwmon/pmbus/Kconfig
> > @@ -397,6 +397,15 @@ config SENSORS_TPS53679
> >         This driver can also be built as a module. If so, the module will
> >         be called tps53679.
> >
> > +config SENSORS_TPS546D24
> > +     tristate "TPS546D24"
> > +     help
> > +       If you say yes here you get hardware monitoring support for TEXAS
> > +       TPS546D24.
> > +
> > +       This driver can also be built as a module. If so, the module will
> > +       be called tps546d24
> > +
> >  config SENSORS_UCD9000
> >       tristate "TI UCD90120, UCD90124, UCD90160, UCD90320, UCD9090, UCD90910"
> >       help
> > diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
> > index e2fe86f..0002dbe 100644
> > --- a/drivers/hwmon/pmbus/Makefile
> > +++ b/drivers/hwmon/pmbus/Makefile
> > @@ -41,6 +41,7 @@ obj-$(CONFIG_SENSORS_Q54SJ108A2)    += q54sj108a2.o
> >  obj-$(CONFIG_SENSORS_STPDDC60)       += stpddc60.o
> >  obj-$(CONFIG_SENSORS_TPS40422)       += tps40422.o
> >  obj-$(CONFIG_SENSORS_TPS53679)       += tps53679.o
> > +obj-$(CONFIG_SENSORS_TPS546D24)      += tps546d24.o
> >  obj-$(CONFIG_SENSORS_UCD9000)        += ucd9000.o
> >  obj-$(CONFIG_SENSORS_UCD9200)        += ucd9200.o
> >  obj-$(CONFIG_SENSORS_XDPE122)        += xdpe12284.o
> > diff --git a/drivers/hwmon/pmbus/tps546d24.c b/drivers/hwmon/pmbus/tps546d24.c
> > new file mode 100644
> > index 0000000..f6f79d3
> > --- /dev/null
> > +++ b/drivers/hwmon/pmbus/tps546d24.c
> > @@ -0,0 +1,73 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +/*
> > + * Hardware monitoring driver for TEXAS TPS546D24 buck converter
> > + */
> > +
> > +#include <linux/err.h>
> > +#include <linux/i2c.h>
> > +#include <linux/init.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/pmbus.h>
> > +#include "pmbus.h"
> > +
> > +static int tps546d24_read_byte_data(struct i2c_client *client, int page, int reg)
> > +{
> > +     int ret;
> > +
> > +     switch (reg) {
> > +     case PMBUS_VOUT_MODE:
> > +             ret = 0x17;
> > +             break;
> > +     default:
> > +             ret = -ENODATA;
> > +             break;
> > +     }
> > +     return ret;
> > +}
> > +
> > +static struct pmbus_driver_info tps546d24_info = {
> > +     .pages = 1,
> > +     .format[PSC_VOLTAGE_IN] = linear,
> > +     .format[PSC_VOLTAGE_OUT] = linear,
> > +     .format[PSC_TEMPERATURE] = linear,
> > +     .format[PSC_CURRENT_OUT] = linear,
> > +     .func[0] = PMBUS_HAVE_VIN | PMBUS_HAVE_IIN |
> > +         PMBUS_HAVE_IOUT | PMBUS_HAVE_VOUT |
> > +             PMBUS_HAVE_STATUS_IOUT | PMBUS_HAVE_STATUS_VOUT |
> > +             PMBUS_HAVE_TEMP | PMBUS_HAVE_STATUS_TEMP,
> > +     .read_byte_data = tps546d24_read_byte_data,
>
> The chip supports multiple phases, and per-phase telemetry.
> Have you considered supporting it ?
>
> > +};
> > +
> > +static int tps546d24_probe(struct i2c_client *client)
> > +{
> > +     return pmbus_do_probe(client, &tps546d24_info);
> > +}
> > +
> > +static const struct i2c_device_id tps546d24_id[] = {
> > +     {"tps546d24", 0},
> > +     {}
> > +};
> > +MODULE_DEVICE_TABLE(i2c, tps546d24_id);
> > +
> > +static const struct of_device_id __maybe_unused tps546d24_of_match[] = {
> > +     {.compatible = "tps546d24"},
>
> This needs a vendor prefix.
>
> > +     {}
> > +};
> > +
> > +/* This is the driver that will be inserted */
> > +static struct i2c_driver tps546d24_driver = {
> > +     .driver = {
> > +                .name = "tps546d24",
> > +                .of_match_table = of_match_ptr(tps546d24_of_match),
> > +        },
> > +     .probe_new = tps546d24_probe,
> > +     .id_table = tps546d24_id,
> > +};
> > +
> > +module_i2c_driver(tps546d24_driver);
> > +
> > +MODULE_AUTHOR("Duke Du <dukedu83@xxxxxxxxx>");
> > +MODULE_DESCRIPTION("PMBus driver for TI tps546d24");
> > +MODULE_LICENSE("GPL");
> > +MODULE_IMPORT_NS(PMBUS);
> > --
> > 2.7.4
> >