Re: [PATCH 11/14] hwmon: peci: Add cputemp driver

["Winiarska, Iwona" <iwona.winiarska@intel.com>]

On Tue, 2021-07-27 at 07:06 +0000, Zev Weiss wrote:
> On Mon, Jul 12, 2021 at 05:04:44PM CDT, Iwona Winiarska wrote:
> > Add peci-cputemp driver for Digital Thermal Sensor (DTS) thermal
> > readings of the processor package and processor cores that are
> > accessible via the PECI interface.
> > 
> > The main use case for the driver (and PECI interface) is out-of-band
> > management, where we're able to obtain the DTS readings from an external
> > entity connected with PECI, e.g. BMC on server platforms.
> > 
> > Co-developed-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
> > Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
> > Signed-off-by: Iwona Winiarska <iwona.winiarska@intel.com>
> > Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> > ---
> > MAINTAINERS                  |   7 +
> > drivers/hwmon/Kconfig        |   2 +
> > drivers/hwmon/Makefile       |   1 +
> > drivers/hwmon/peci/Kconfig   |  18 ++
> > drivers/hwmon/peci/Makefile  |   5 +
> > drivers/hwmon/peci/common.h  |  46 ++++
> > drivers/hwmon/peci/cputemp.c | 503 +++++++++++++++++++++++++++++++++++
> > 7 files changed, 582 insertions(+)
> > create mode 100644 drivers/hwmon/peci/Kconfig
> > create mode 100644 drivers/hwmon/peci/Makefile
> > create mode 100644 drivers/hwmon/peci/common.h
> > create mode 100644 drivers/hwmon/peci/cputemp.c
> > 
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index f47b5f634293..35ba9e3646bd 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -14504,6 +14504,13 @@ L:     platform-driver-x86@vger.kernel.org
> > S:      Maintained
> > F:      drivers/platform/x86/peaq-wmi.c
> > 
> > +PECI HARDWARE MONITORING DRIVERS
> > +M:     Iwona Winiarska <iwona.winiarska@intel.com>
> > +R:     Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
> > +L:     linux-hwmon@vger.kernel.org
> > +S:     Supported
> > +F:     drivers/hwmon/peci/
> > +
> > PECI SUBSYSTEM
> > M:      Iwona Winiarska <iwona.winiarska@intel.com>
> > R:      Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index e3675377bc5d..61c0e3404415 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -1507,6 +1507,8 @@ config SENSORS_PCF8591
> >           These devices are hard to detect and rarely found on mainstream
> >           hardware. If unsure, say N.
> > 
> > +source "drivers/hwmon/peci/Kconfig"
> > +
> > source "drivers/hwmon/pmbus/Kconfig"
> > 
> > config SENSORS_PWM_FAN
> > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> > index d712c61c1f5e..f52331f212ed 100644
> > --- a/drivers/hwmon/Makefile
> > +++ b/drivers/hwmon/Makefile
> > @@ -202,6 +202,7 @@ obj-$(CONFIG_SENSORS_WM8350)        += wm8350-hwmon.o
> > obj-$(CONFIG_SENSORS_XGENE)     += xgene-hwmon.o
> > 
> > obj-$(CONFIG_SENSORS_OCC)       += occ/
> > +obj-$(CONFIG_SENSORS_PECI)     += peci/
> > obj-$(CONFIG_PMBUS)             += pmbus/
> > 
> > ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
> > diff --git a/drivers/hwmon/peci/Kconfig b/drivers/hwmon/peci/Kconfig
> > new file mode 100644
> > index 000000000000..e10eed68d70a
> > --- /dev/null
> > +++ b/drivers/hwmon/peci/Kconfig
> > @@ -0,0 +1,18 @@
> > +# SPDX-License-Identifier: GPL-2.0-only
> > +
> > +config SENSORS_PECI_CPUTEMP
> > +       tristate "PECI CPU temperature monitoring client"
> > +       depends on PECI
> > +       select SENSORS_PECI
> > +       select PECI_CPU
> > +       help
> > +         If you say yes here you get support for the generic Intel PECI
> > +         cputemp driver which provides Digital Thermal Sensor (DTS) thermal
> > +         readings of the CPU package and CPU cores that are accessible via
> > +         the processor PECI interface.
> > +
> > +         This driver can also be built as a module. If so, the module
> > +         will be called peci-cputemp.
> > +
> > +config SENSORS_PECI
> > +       tristate
> > diff --git a/drivers/hwmon/peci/Makefile b/drivers/hwmon/peci/Makefile
> > new file mode 100644
> > index 000000000000..e8a0ada5ab1f
> > --- /dev/null
> > +++ b/drivers/hwmon/peci/Makefile
> > @@ -0,0 +1,5 @@
> > +# SPDX-License-Identifier: GPL-2.0-only
> > +
> > +peci-cputemp-y := cputemp.o
> > +
> > +obj-$(CONFIG_SENSORS_PECI_CPUTEMP)     += peci-cputemp.o
> > diff --git a/drivers/hwmon/peci/common.h b/drivers/hwmon/peci/common.h
> > new file mode 100644
> > index 000000000000..54580c100d06
> > --- /dev/null
> > +++ b/drivers/hwmon/peci/common.h
> > @@ -0,0 +1,46 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +/* Copyright (c) 2021 Intel Corporation */
> > +
> > +#include <linux/types.h>
> > +
> > +#ifndef __PECI_HWMON_COMMON_H
> > +#define __PECI_HWMON_COMMON_H
> > +
> > +#define UPDATE_INTERVAL_DEFAULT                HZ
> > +
> > +/**
> > + * struct peci_sensor_data - PECI sensor information
> > + * @valid: flag to indicate the sensor value is valid
> > + * @value: sensor value in milli units
> > + * @last_updated: time of the last update in jiffies
> > + */
> > +struct peci_sensor_data {
> > +       unsigned int valid;
> 
> From what I can see it looks like the 'valid' member here is strictly a
> one-shot has-this-value-ever-been-set indicator, which seems a bit
> wasteful to keep around forever post initialization; couldn't the same
> information be inferred from checking last_updated != 0 or something?

That's just expressed in jiffies, which means it can overflow (we're just
unlikely to hit it - but IIUC it can happen).
Doing it this way would require making sure that last_updated is never set to 0
in code that does the update. I don't think it's worth to add more complexity
there just to save a couple of bytes.

> 
> > +       s32 value;
> > +       unsigned long last_updated;
> > +};
> > +
> > +/**
> > + * peci_sensor_need_update() - check whether sensor update is needed or not
> > + * @sensor: pointer to sensor data struct
> > + *
> > + * Return: true if update is needed, false if not.
> > + */
> > +
> > +static inline bool peci_sensor_need_update(struct peci_sensor_data *sensor)
> > +{
> > +       return !sensor->valid ||
> > +              time_after(jiffies, sensor->last_updated +
> > UPDATE_INTERVAL_DEFAULT);
> > +}
> > +
> > +/**
> > + * peci_sensor_mark_updated() - mark the sensor is updated
> > + * @sensor: pointer to sensor data struct
> > + */
> > +static inline void peci_sensor_mark_updated(struct peci_sensor_data
> > *sensor)
> > +{
> > +       sensor->valid = 1;
> > +       sensor->last_updated = jiffies;
> > +}
> > +
> > +#endif /* __PECI_HWMON_COMMON_H */
> > diff --git a/drivers/hwmon/peci/cputemp.c b/drivers/hwmon/peci/cputemp.c
> > new file mode 100644
> > index 000000000000..56a526471687
> > --- /dev/null
> > +++ b/drivers/hwmon/peci/cputemp.c
> > @@ -0,0 +1,503 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +// Copyright (c) 2018-2021 Intel Corporation
> > +
> > +#include <linux/auxiliary_bus.h>
> > +#include <linux/bitfield.h>
> > +#include <linux/bitops.h>
> > +#include <linux/hwmon.h>
> > +#include <linux/jiffies.h>
> > +#include <linux/module.h>
> > +#include <linux/peci.h>
> > +#include <linux/peci-cpu.h>
> > +#include <linux/units.h>
> > +#include <linux/x86/intel-family.h>
> > +
> > +#include "common.h"
> > +
> > +#define CORE_NUMS_MAX          64
> > +
> > +#define DEFAULT_CHANNEL_NUMS   5
> 
> DEFAULT_ seems like a slightly odd prefix for this (it's not something
> that can really be overridden or anything); would BASE_ perhaps be a bit
> more appropriate?

Ack.

> 
> > +#define CORETEMP_CHANNEL_NUMS  CORE_NUMS_MAX
> > +#define CPUTEMP_CHANNEL_NUMS   (DEFAULT_CHANNEL_NUMS +
> > CORETEMP_CHANNEL_NUMS)
> > +
> > +#define TEMP_TARGET_FAN_TEMP_MASK      GENMASK(15, 8)
> > +#define TEMP_TARGET_REF_TEMP_MASK      GENMASK(23, 16)
> > +#define TEMP_TARGET_TJ_OFFSET_MASK     GENMASK(29, 24)
> > +
> > +#define DTS_MARGIN_MASK                GENMASK(15, 0)
> > +#define PCS_MODULE_TEMP_MASK   GENMASK(15, 0)
> > +
> > +#define DTS_FIXED_POINT_FRACTION       64
> > +
> > +struct resolved_cores_reg {
> > +       u8 bus;
> > +       u8 dev;
> > +       u8 func;
> > +       u8 offset;
> > +};
> > +
> > +struct cpu_info {
> > +       struct resolved_cores_reg *reg;
> > +       u8 min_peci_revision;
> 
> As with the dimmtemp driver, min_peci_revision appears unused here,
> though in this case if it were removed there'd only be one (pointer)
> member left in struct cpu_info, so we could perhaps remove it as well
> and then also a level of indirection in peci_cputemp_ids/cpu_{hsx,icx}
> too?

As I mentioned in reply to previous patch comment, it'll be used to validate if
PECI device revision matches driver requirements.

> 
> > +};
> > +
> > +struct peci_cputemp {
> > +       struct peci_device *peci_dev;
> > +       struct device *dev;
> > +       const char *name;
> > +       const struct cpu_info *gen_info;
> > +       struct {
> > +               struct peci_sensor_data die;
> > +               struct peci_sensor_data dts;
> > +               struct peci_sensor_data tcontrol;
> > +               struct peci_sensor_data tthrottle;
> > +               struct peci_sensor_data tjmax;
> > +               struct peci_sensor_data core[CORETEMP_CHANNEL_NUMS];
> > +       } temp;
> > +       const char **coretemp_label;
> > +       DECLARE_BITMAP(core_mask, CORE_NUMS_MAX);
> > +};
> > +
> > +enum cputemp_channels {
> > +       channel_die,
> > +       channel_dts,
> > +       channel_tcontrol,
> > +       channel_tthrottle,
> > +       channel_tjmax,
> > +       channel_core,
> > +};
> > +
> > +static const char *cputemp_label[DEFAULT_CHANNEL_NUMS] = {
> 
> static const char * const cputemp_label?  (That is, const pointer to
> const char, rather than non-const pointer to const char.)

Ack.

> 
> > +       "Die",
> > +       "DTS",
> > +       "Tcontrol",
> > +       "Tthrottle",
> > +       "Tjmax",
> > +};
> > +
> > +static int get_temp_targets(struct peci_cputemp *priv)
> > +{
> > +       s32 tthrottle_offset, tcontrol_margin;
> > +       u32 pcs;
> > +       int ret;
> > +
> > +       /*
> > +        * Just use only the tcontrol marker to determine if target values
> > need
> > +        * update.
> > +        */
> > +       if (!peci_sensor_need_update(&priv->temp.tcontrol))
> > +               return 0;
> > +
> > +       ret = peci_pcs_read(priv->peci_dev, PECI_PCS_TEMP_TARGET, 0, &pcs);
> > +       if (ret)
> > +               return ret;
> > +
> > +       priv->temp.tjmax.value = FIELD_GET(TEMP_TARGET_REF_TEMP_MASK, pcs) *
> > MILLIDEGREE_PER_DEGREE;
> > +
> > +       tcontrol_margin = FIELD_GET(TEMP_TARGET_FAN_TEMP_MASK, pcs);
> > +       tcontrol_margin = sign_extend32(tcontrol_margin, 7) *
> > MILLIDEGREE_PER_DEGREE;
> > +       priv->temp.tcontrol.value = priv->temp.tjmax.value -
> > tcontrol_margin;
> > +
> > +       tthrottle_offset = FIELD_GET(TEMP_TARGET_TJ_OFFSET_MASK, pcs) *
> > MILLIDEGREE_PER_DEGREE;
> > +       priv->temp.tthrottle.value = priv->temp.tjmax.value -
> > tthrottle_offset;
> > +
> > +       peci_sensor_mark_updated(&priv->temp.tcontrol);
> > +
> > +       return 0;
> > +}
> > +
> > +/*
> > + * Processors return a value of DTS reading in S10.6 fixed point format
> > + * (sign, 10 bits signed integer value, 6 bits fractional).
> 
> This parenthetical reads to me like it's describing 17 bits -- I'm not a
> PECI expert, but from my reading of the (somewhat skimpy) docs I've got
> on it I'd suggest a description more like "sign, 9-bit magnitude, 6-bit
> fraction".

You're right, adding "sign" here was not intentional.
I'll change it to:
"16 bits: sign, 9-bit magnitude, 6-bit fraction"
or
"16 bits: 10-bit signed magnitude, 6-bit fraction"

Thanks
-Iwona