Message-ID: <20190507183536.GB29510@roeck-us.net>
Date:   Tue, 7 May 2019 11:35:36 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Alan Tull <atull@...nel.org>
Cc:     Wu Hao <hao.wu@...el.com>, Moritz Fischer <mdf@...nel.org>,
        linux-fpga@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-api@...r.kernel.org, Luwei Kang <luwei.kang@...el.com>,
        Russ Weight <russell.h.weight@...el.com>,
        Xu Yilun <yilun.xu@...el.com>,
        Jean Delvare <jdelvare@...e.com>,
        Linux HWMON List <linux-hwmon@...r.kernel.org>
Subject: Re: [PATCH v2 15/18] fpga: dfl: fme: add thermal management support

On Tue, May 07, 2019 at 01:20:52PM -0500, Alan Tull wrote:
> On Mon, Apr 29, 2019 at 4:13 AM Wu Hao <hao.wu@...el.com> wrote:
> 
> + The hwmon people
> 
> >
> > This patch adds support to thermal management private feature for DFL
> > FPGA Management Engine (FME). This private feature driver registers
> > a hwmon for thermal/temperature monitoring (hwmon temp1_input).
> > If hardware automatic throttling is supported by this hardware, then
> > driver also exposes sysfs interfaces under hwmon for thresholds
> > (temp1_alarm/ crit/ emergency), threshold status (temp1_alarm_status/
> > temp1_crit_status) and throttling policy (temp1_alarm_policy).
> >
> > Signed-off-by: Luwei Kang <luwei.kang@...el.com>
> > Signed-off-by: Russ Weight <russell.h.weight@...el.com>
> > Signed-off-by: Xu Yilun <yilun.xu@...el.com>
> > Signed-off-by: Wu Hao <hao.wu@...el.com>
> > ---
> > v2: create a dfl_fme_thermal hwmon to expose thermal information.
> >     move all sysfs interfaces under hwmon
> >         tempareture       --> hwmon temp1_input
> >         threshold1        --> hwmon temp1_alarm
> >         threshold2        --> hwmon temp1_crit
> >         trip_threshold    --> hwmon temp1_emergency
> >         threshold1_status --> hwmon temp1_alarm_status
> >         threshold2_status --> hwmon temp1_crit_status
> >         threshold1_policy --> hwmon temp1_alarm_policy

You should not write a hwmon driver if you don't want to follow the ABI.
The implementation will only confuse the sensors command, so what exactly
is the point ?

More on that below.

Guenter

> > ---
> >  Documentation/ABI/testing/sysfs-platform-dfl-fme |  64 +++++++
> >  drivers/fpga/Kconfig                             |   2 +-
> >  drivers/fpga/dfl-fme-main.c                      | 212 +++++++++++++++++++++++
> >  3 files changed, 277 insertions(+), 1 deletion(-)
> >
> > diff --git a/Documentation/ABI/testing/sysfs-platform-dfl-fme b/Documentation/ABI/testing/sysfs-platform-dfl-fme
> > index d1aa375..dfbd315 100644
> > --- a/Documentation/ABI/testing/sysfs-platform-dfl-fme
> > +++ b/Documentation/ABI/testing/sysfs-platform-dfl-fme
> > @@ -44,3 +44,67 @@ Description: Read-only. It returns socket_id to indicate which socket
> >                 this FPGA belongs to, only valid for integrated solution.
> >                 User only needs this information, in case standard numa node
> >                 can't provide correct information.
> > +
> > +What:          /sys/bus/platform/devices/dfl-fme.0/hwmon/hwmonX/name
> > +Date:          April 2019
> > +KernelVersion: 5.2
> > +Contact:       Wu Hao <hao.wu@...el.com>
> > +Description:   Read-Only. Read this file to get the name of hwmon device, it
> > +               supports values:
> > +                   'dfl_fme_thermal' - thermal hwmon device name
> > +
> > +What:          /sys/bus/platform/devices/dfl-fme.0/hwmon/hwmonX/temp1_input
> > +Date:          April 2019
> > +KernelVersion: 5.2
> > +Contact:       Wu Hao <hao.wu@...el.com>
> > +Description:   Read-Only. It returns FPGA device temperature in millidegrees
> > +               Celsius.
> > +
> > +What:          /sys/bus/platform/devices/dfl-fme.0/hwmon/hwmonX/temp1_alarm
> > +Date:          April 2019
> > +KernelVersion: 5.2
> > +Contact:       Wu Hao <hao.wu@...el.com>
> > +Description:   Read-Only. It returns hardware threshold1 temperature in
> > +               millidegrees Celsius. If temperature rises at or above this
> > +               threshold, hardware starts 50% or 90% throttling (see
> > +               'temp1_alarm_policy').
> > +

This does not follow the ABI. temp1_alarm is the alarm status, not the alarm
temperature. The ABI attribute name would be temp1_max.

> > +What:          /sys/bus/platform/devices/dfl-fme.0/hwmon/hwmonX/temp1_crit
> > +Date:          April 2019
> > +KernelVersion: 5.2
> > +Contact:       Wu Hao <hao.wu@...el.com>
> > +Description:   Read-Only. It returns hardware threshold2 temperature in
> > +               millidegrees Celsius. If temperature rises at or above this
> > +               threshold, hardware starts 100% throttling.
> > +
> > +What:          /sys/bus/platform/devices/dfl-fme.0/hwmon/hwmonX/temp1_emergency
> > +Date:          April 2019
> > +KernelVersion: 5.2
> > +Contact:       Wu Hao <hao.wu@...el.com>
> > +Description:   Read-Only. It returns hardware trip threshold temperature in
> > +               millidegrees Celsius. If temperature rises at or above this
> > +               threshold, a fatal event will be triggered to board management
> > +               controller (BMC) to shutdown FPGA.
> > +
> > +What:          /sys/bus/platform/devices/dfl-fme.0/hwmon/hwmonX/temp1_alarm_status
> > +Date:          April 2019
> > +KernelVersion: 5.2
> > +Contact:       Wu Hao <hao.wu@...el.com>
> > +Description:   Read-only. It returns 1 if temperature is currently at or above
> > +               hardware threshold1 (see 'temp1_alarm'), otherwise 0.
> > +

Why not follow the ABI and use temp1_alarm ?

> > +What:          /sys/bus/platform/devices/dfl-fme.0/hwmon/hwmonX/temp1_crit_status
> > +Date:          April 2019
> > +KernelVersion: 5.2
> > +Contact:       Wu Hao <hao.wu@...el.com>
> > +Description:   Read-only. It returns 1 if temperature is currently at or above
> > +               hardware threshold2 (see 'temp1_crit'), otherwise 0.
> > +

Why not follow the ABI and use temp1_crit_alarm ?

> > +What:          /sys/bus/platform/devices/dfl-fme.0/hwmon/hwmonX/temp1_alarm_policy
> > +Date:          April 2019
> > +KernelVersion: 5.2
> > +Contact:       Wu Hao <hao.wu@...el.com>
> > +Description:   Read-Only. Read this file to get the policy of hardware threshold1
> > +               (see 'temp1_alarm'). It only supports two values (policies):
> > +                   0 - AP2 state (90% throttling)
> > +                   1 - AP1 state (50% throttling)
> > diff --git a/drivers/fpga/Kconfig b/drivers/fpga/Kconfig
> > index c20445b..a6d7588 100644
> > --- a/drivers/fpga/Kconfig
> > +++ b/drivers/fpga/Kconfig
> > @@ -154,7 +154,7 @@ config FPGA_DFL
> >
> >  config FPGA_DFL_FME
> >         tristate "FPGA DFL FME Driver"
> > -       depends on FPGA_DFL
> > +       depends on FPGA_DFL && HWMON
> >         help
> >           The FPGA Management Engine (FME) is a feature device implemented
> >           under Device Feature List (DFL) framework. Select this option to
> > diff --git a/drivers/fpga/dfl-fme-main.c b/drivers/fpga/dfl-fme-main.c
> > index 8339ee8..b9a68b8 100644
> > --- a/drivers/fpga/dfl-fme-main.c
> > +++ b/drivers/fpga/dfl-fme-main.c
> > @@ -14,6 +14,8 @@
> >   *   Henry Mitchel <henry.mitchel@...el.com>
> >   */
> >
> > +#include <linux/hwmon.h>
> > +#include <linux/hwmon-sysfs.h>
> >  #include <linux/kernel.h>
> >  #include <linux/module.h>
> >  #include <linux/uaccess.h>
> > @@ -217,6 +219,212 @@ static long fme_hdr_ioctl(struct platform_device *pdev,
> >         .ioctl = fme_hdr_ioctl,
> >  };
> >
> > +#define FME_THERM_THRESHOLD    0x8
> > +#define TEMP_THRESHOLD1                GENMASK_ULL(6, 0)
> > +#define TEMP_THRESHOLD1_EN     BIT_ULL(7)
> > +#define TEMP_THRESHOLD2                GENMASK_ULL(14, 8)
> > +#define TEMP_THRESHOLD2_EN     BIT_ULL(15)
> > +#define TRIP_THRESHOLD         GENMASK_ULL(30, 24)
> > +#define TEMP_THRESHOLD1_STATUS BIT_ULL(32)             /* threshold1 reached */
> > +#define TEMP_THRESHOLD2_STATUS BIT_ULL(33)             /* threshold2 reached */
> > +/* threshold1 policy: 0 - AP2 (90% throttle) / 1 - AP1 (50% throttle) */
> > +#define TEMP_THRESHOLD1_POLICY BIT_ULL(44)
> > +
> > +#define FME_THERM_RDSENSOR_FMT1        0x10
> > +#define FPGA_TEMPERATURE       GENMASK_ULL(6, 0)
> > +
> > +#define FME_THERM_CAP          0x20
> > +#define THERM_NO_THROTTLE      BIT_ULL(0)
> > +
> > +#define MD_PRE_DEG
> > +
> > +static bool fme_thermal_throttle_support(void __iomem *base)
> > +{
> > +       u64 v = readq(base + FME_THERM_CAP);
> > +
> > +       return FIELD_GET(THERM_NO_THROTTLE, v) ? false : true;
> > +}
> > +
> > +static umode_t thermal_hwmon_attrs_visible(const void *drvdata,
> > +                                          enum hwmon_sensor_types type,
> > +                                          u32 attr, int channel)
> > +{
> > +       const struct dfl_feature *feature = drvdata;
> > +
> > +       /* temperature is always supported, and check hardware cap for others */
> > +       if (attr == hwmon_temp_input)
> > +               return 0444;
> > +
> > +       return fme_thermal_throttle_support(feature->ioaddr) ? 0444 : 0;
> > +}
> > +
> > +static int thermal_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
> > +                             u32 attr, int channel, long *val)
> > +{
> > +       struct dfl_feature *feature = dev_get_drvdata(dev);
> > +       u64 v;
> > +
> > +       switch (attr) {
> > +       case hwmon_temp_input:
> > +               v = readq(feature->ioaddr + FME_THERM_RDSENSOR_FMT1);
> > +               *val = (long)(FIELD_GET(FPGA_TEMPERATURE, v) * 1000);
> > +               break;
> > +       case hwmon_temp_alarm:
> > +               v = readq(feature->ioaddr + FME_THERM_THRESHOLD);
> > +               *val = (long)(FIELD_GET(TEMP_THRESHOLD1, v) * 1000);

This is supposed to return 0 or 1.

> > +               break;
> > +       case hwmon_temp_crit:
> > +               v = readq(feature->ioaddr + FME_THERM_THRESHOLD);
> > +               *val = (long)(FIELD_GET(TEMP_THRESHOLD2, v) * 1000);
> > +               break;
> > +       case hwmon_temp_emergency:
> > +               v = readq(feature->ioaddr + FME_THERM_THRESHOLD);
> > +               *val = (long)(FIELD_GET(TRIP_THRESHOLD, v) * 1000);
> > +               break;
> > +       default:
> > +               return -EOPNOTSUPP;
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> > +static const struct hwmon_ops thermal_hwmon_ops = {
> > +       .is_visible = thermal_hwmon_attrs_visible,
> > +       .read = thermal_hwmon_read,
> > +};
> > +
> > +static const u32 thermal_hwmon_temp_config[] = {
> > +       HWMON_T_INPUT | HWMON_T_ALARM | HWMON_T_CRIT | HWMON_T_EMERGENCY,
> > +       0
> > +};
> > +
> > +static const struct hwmon_channel_info hwmon_temp_info = {
> > +       .type = hwmon_temp,
> > +       .config = thermal_hwmon_temp_config,
> > +};
> > +
> > +static const struct hwmon_channel_info *thermal_hwmon_info[] = {
> > +       &hwmon_temp_info,
> > +       NULL
> > +};
> > +
> > +static const struct hwmon_chip_info thermal_hwmon_chip_info = {
> > +       .ops = &thermal_hwmon_ops,
> > +       .info = thermal_hwmon_info,
> > +};
> > +
> > +static ssize_t temp1_alarm_status_show(struct device *dev,
> > +                                      struct device_attribute *attr, char *buf)
> > +{
> > +       struct dfl_feature *feature = dev_get_drvdata(dev);
> > +       u64 v;
> > +
> > +       v = readq(feature->ioaddr + FME_THERM_THRESHOLD);
> > +
> > +       return scnprintf(buf, PAGE_SIZE, "%u\n",
> > +                        (unsigned int)FIELD_GET(TEMP_THRESHOLD1_STATUS, v));
> > +}
> > +
> > +static ssize_t temp1_crit_status_show(struct device *dev,
> > +                                     struct device_attribute *attr, char *buf)
> > +{
> > +       struct dfl_feature *feature = dev_get_drvdata(dev);
> > +       u64 v;
> > +
> > +       v = readq(feature->ioaddr + FME_THERM_THRESHOLD);
> > +
> > +       return scnprintf(buf, PAGE_SIZE, "%u\n",
> > +                        (unsigned int)FIELD_GET(TEMP_THRESHOLD2_STATUS, v));
> > +}
> > +
> > +static ssize_t temp1_alarm_policy_show(struct device *dev,
> > +                                      struct device_attribute *attr, char *buf)
> > +{
> > +       struct dfl_feature *feature = dev_get_drvdata(dev);
> > +       u64 v;
> > +
> > +       v = readq(feature->ioaddr + FME_THERM_THRESHOLD);
> > +
> > +       return scnprintf(buf, PAGE_SIZE, "%u\n",
> > +                        (unsigned int)FIELD_GET(TEMP_THRESHOLD1_POLICY, v));
> > +}
> > +
> > +static DEVICE_ATTR_RO(temp1_alarm_status);
> > +static DEVICE_ATTR_RO(temp1_crit_status);
> > +static DEVICE_ATTR_RO(temp1_alarm_policy);
> > +
> > +static struct attribute *thermal_extra_attrs[] = {
> > +       &dev_attr_temp1_alarm_status.attr,
> > +       &dev_attr_temp1_crit_status.attr,

Why not use standard attributes for the above ?

> > +       &dev_attr_temp1_alarm_policy.attr,
> > +       NULL,
> > +};
> > +
> > +static umode_t thermal_extra_attrs_visible(struct kobject *kobj,
> > +                                          struct attribute *attr, int index)
> > +{
> > +       struct device *dev = kobj_to_dev(kobj);
> > +       struct dfl_feature *feature = dev_get_drvdata(dev);
> > +
> > +       return fme_thermal_throttle_support(feature->ioaddr) ? attr->mode : 0;
> > +}
> > +
> > +static const struct attribute_group thermal_extra_group = {
> > +       .attrs          = thermal_extra_attrs,
> > +       .is_visible     = thermal_extra_attrs_visible,
> > +};
> > +__ATTRIBUTE_GROUPS(thermal_extra);
> > +
> > +static int fme_thermal_mgmt_init(struct platform_device *pdev,
> > +                                struct dfl_feature *feature)
> > +{
> > +       struct device *hwmon;
> > +
> > +       dev_dbg(&pdev->dev, "FME Thermal Management Init.\n");
> > +
> > +       /*
> > +        * create hwmon to allow userspace monitoring temperature and other
> > +        * threshold information.
> > +        *
> > +        * temp1_alarm     -> hardware threshold 1 -> 50% or 90% throttling
> > +        * temp1_crit      -> hardware threshold 2 -> 100% throttling
> > +        * temp1_emergency -> hardware trip_threshold to shutdown FPGA
> > +        *
> > +        * create device specific sysfs interfaces, e.g. read temp1_alarm_policy
> > +        * to understand the actual hardware throttling action (50% vs 90%).
> > +        *
> > +        * If hardware doesn't support automatic throttling per thresholds,
> > +        * then all above sysfs interfaces are not visible except temp1_input
> > +        * for temperature.
> > +        */
> > +       hwmon = devm_hwmon_device_register_with_info(&pdev->dev,
> > +                                                    "dfl_fme_thermal", feature,
> > +                                                    &thermal_hwmon_chip_info,
> > +                                                    thermal_extra_groups);
> > +       if (IS_ERR(hwmon)) {
> > +               dev_err(&pdev->dev, "Fail to register thermal hwmon\n");
> > +               return PTR_ERR(hwmon);
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> > +static void fme_thermal_mgmt_uinit(struct platform_device *pdev,
> > +                                  struct dfl_feature *feature)
> > +{
> > +       dev_dbg(&pdev->dev, "FME Thermal Management UInit.\n");
> > +}
> > +
> > +static const struct dfl_feature_id fme_thermal_mgmt_id_table[] = {
> > +       {.id = FME_FEATURE_ID_THERMAL_MGMT,},
> > +       {0,}
> > +};
> > +
> > +static const struct dfl_feature_ops fme_thermal_mgmt_ops = {
> > +       .init = fme_thermal_mgmt_init,
> > +       .uinit = fme_thermal_mgmt_uinit,
> > +};
> > +
> >  static struct dfl_feature_driver fme_feature_drvs[] = {
> >         {
> >                 .id_table = fme_hdr_id_table,
> > @@ -227,6 +435,10 @@ static long fme_hdr_ioctl(struct platform_device *pdev,
> >                 .ops = &fme_pr_mgmt_ops,
> >         },
> >         {
> > +               .id_table = fme_thermal_mgmt_id_table,
> > +               .ops = &fme_thermal_mgmt_ops,
> > +       },
> > +       {
> >                 .ops = NULL,
> >         },
> >  };
> > --
> > 1.8.3.1
> >

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