Re: [PATCH] hwmon (occ): Avoid polling OCC during probe

[Eddie James <eajames@xxxxxxxxxxxxx>]

On 4/26/22 10:01, Guenter Roeck wrote:
> On 4/26/22 07:45, Eddie James wrote:
> > Instead of polling the OCC during the probe, use the "occ_active"
> > sysfs file to control when the driver polls the OCC for sensor data.
> > The reason for this change is that the SBE, which is the device by
> > which the driver communicates with the OCC, cannot handle communications
> > during certain system state transitions.
>
> This is hackish, to say the least. Why not just instantiate the driver
> manually instead if userspace interaction is indeed needed, and there
> is no means to auto-instantiate it only after the hardware is ready ?


Well, the occ-hwmon platform devices are currently created by the parent 
FSI occ device (that's a bit of a hack too). I poked through the 
platform/device/bus interfaces but couldn't work out how to create the 
device but not probe it, so that userspace could later bind the device 
to the driver. The current userspace does just that, but it relies on 
the the initial probe failing since SBE can't handle the communications 
yet. The error scenario is that the SBE can get into a bad state, so 
communications shouldn't even be attempted.

So to answer your question, there's no reason not to just instantiate 
the driver manually, but I don't actually know how to do so with these 
drivers.


> On the other side, what means does userspace have to determine that
> the SBE/OCC is ready ? Can't that same mechanism not be used in the
> kernel to auto-instantiate the driver ?


No it's impossible, it's not just some bit we can check in HW 
unfortunately, the signal is PLDM (platform level data model) over the 
network.


Thanks for your quick response.

Eddie


> Guenter
>
> > Signed-off-by: Eddie James <eajames@xxxxxxxxxxxxx>
> > ---
> >   drivers/hwmon/occ/common.c | 100 +++++++++++++++++++--------
> >   drivers/hwmon/occ/common.h |   5 +-
> >   drivers/hwmon/occ/p8_i2c.c |   2 +-
> >   drivers/hwmon/occ/p9_sbe.c |   2 +-
> >   drivers/hwmon/occ/sysfs.c  | 137 ++++++++++++++++++++++---------------
> >   5 files changed, 156 insertions(+), 90 deletions(-)
> >
> > diff --git a/drivers/hwmon/occ/common.c b/drivers/hwmon/occ/common.c
> > index f00cd59f1d19..d78f4bebc718 100644
> > --- a/drivers/hwmon/occ/common.c
> > +++ b/drivers/hwmon/occ/common.c
> > @@ -1149,44 +1149,75 @@ static void occ_parse_poll_response(struct 
> > occ *occ)
> >           sizeof(*header), size + sizeof(*header));
> >   }
> >   -int occ_setup(struct occ *occ, const char *name)
> > +int occ_active(struct occ *occ, bool active)
> >   {
> > -    int rc;
> > -
> > -    mutex_init(&occ->lock);
> > -    occ->groups[0] = &occ->group;
> > +    int rc = mutex_lock_interruptible(&occ->lock);
> >   -    /* no need to lock */
> > -    rc = occ_poll(occ);
> > -    if (rc == -ESHUTDOWN) {
> > -        dev_info(occ->bus_dev, "host is not ready\n");
> > -        return rc;
> > -    } else if (rc < 0) {
> > -        dev_err(occ->bus_dev,
> > -            "failed to get OCC poll response=%02x: %d\n",
> > -            occ->resp.return_status, rc);
> > +    if (rc)
> >           return rc;
> > -    }
> >   -    occ->next_update = jiffies + OCC_UPDATE_FREQUENCY;
> > -    occ_parse_poll_response(occ);
> > +    if (active) {
> > +        if (occ->active) {
> > +            rc = -EALREADY;
> > +            goto unlock;
> > +        }
> >   -    rc = occ_setup_sensor_attrs(occ);
> > -    if (rc) {
> > -        dev_err(occ->bus_dev, "failed to setup sensor attrs: %d\n",
> > -            rc);
> > -        return rc;
> > -    }
> > +        occ->error_count = 0;
> > +        occ->last_safe = 0;
> >   -    occ->hwmon = 
> > devm_hwmon_device_register_with_groups(occ->bus_dev, name,
> > -                                occ, occ->groups);
> > -    if (IS_ERR(occ->hwmon)) {
> > -        rc = PTR_ERR(occ->hwmon);
> > -        dev_err(occ->bus_dev, "failed to register hwmon device: %d\n",
> > -            rc);
> > -        return rc;
> > +        rc = occ_poll(occ);
> > +        if (rc < 0) {
> > +            dev_err(occ->bus_dev,
> > +                "failed to get OCC poll response=%02x: %d\n",
> > +                occ->resp.return_status, rc);
> > +            goto unlock;
> > +        }
> > +
> > +        occ->active = true;
> > +        occ->next_update = jiffies + OCC_UPDATE_FREQUENCY;
> > +        occ_parse_poll_response(occ);
> > +
> > +        rc = occ_setup_sensor_attrs(occ);
> > +        if (rc) {
> > +            dev_err(occ->bus_dev,
> > +                "failed to setup sensor attrs: %d\n", rc);
> > +            goto unlock;
> > +        }
> > +
> > +        occ->hwmon = hwmon_device_register_with_groups(occ->bus_dev,
> > +                                   "occ", occ,
> > +                                   occ->groups);
> > +        if (IS_ERR(occ->hwmon)) {
> > +            rc = PTR_ERR(occ->hwmon);
> > +            occ->hwmon = NULL;
> > +            dev_err(occ->bus_dev,
> > +                "failed to register hwmon device: %d\n", rc);
> > +            goto unlock;
> > +        }
> > +    } else {
> > +        if (!occ->active) {
> > +            rc = -EALREADY;
> > +            goto unlock;
> > +        }
> > +
> > +        if (occ->hwmon)
> > +            hwmon_device_unregister(occ->hwmon);
> > +        occ->active = false;
> > +        occ->hwmon = NULL;
> >       }
> >   +unlock:
> > +    mutex_unlock(&occ->lock);
> > +    return rc;
> > +}
> > +
> > +int occ_setup(struct occ *occ)
> > +{
> > +    int rc;
> > +
> > +    mutex_init(&occ->lock);
> > +    occ->groups[0] = &occ->group;
> > +
> >       rc = occ_setup_sysfs(occ);
> >       if (rc)
> >           dev_err(occ->bus_dev, "failed to setup sysfs: %d\n", rc);
> > @@ -1195,6 +1226,15 @@ int occ_setup(struct occ *occ, const char *name)
> >   }
> >   EXPORT_SYMBOL_GPL(occ_setup);
> >   +void occ_shutdown(struct occ *occ)
> > +{
> > +    occ_shutdown_sysfs(occ);
> > +
> > +    if (occ->hwmon)
> > +        hwmon_device_unregister(occ->hwmon);
> > +}
> > +EXPORT_SYMBOL_GPL(occ_shutdown);
> > +
> >   MODULE_AUTHOR("Eddie James <eajames@xxxxxxxxxxxxx>");
> >   MODULE_DESCRIPTION("Common OCC hwmon code");
> >   MODULE_LICENSE("GPL");
> > diff --git a/drivers/hwmon/occ/common.h b/drivers/hwmon/occ/common.h
> > index 2dd4a4d240c0..64d5ec7e169b 100644
> > --- a/drivers/hwmon/occ/common.h
> > +++ b/drivers/hwmon/occ/common.h
> > @@ -106,6 +106,7 @@ struct occ {
> >       struct attribute_group group;
> >       const struct attribute_group *groups[2];
> >   +    bool active;
> >       int error;                      /* final transfer error after 
> > retry */
> >       int last_error;            /* latest transfer error */
> >       unsigned int error_count;       /* number of xfr errors 
> > observed */
> > @@ -123,9 +124,11 @@ struct occ {
> >       u8 prev_mode;
> >   };
> >   -int occ_setup(struct occ *occ, const char *name);
> > +int occ_active(struct occ *occ, bool active);
> > +int occ_setup(struct occ *occ);
> >   int occ_setup_sysfs(struct occ *occ);
> >   void occ_shutdown(struct occ *occ);
> > +void occ_shutdown_sysfs(struct occ *occ);
> >   void occ_sysfs_poll_done(struct occ *occ);
> >   int occ_update_response(struct occ *occ);
> >   diff --git a/drivers/hwmon/occ/p8_i2c.c b/drivers/hwmon/occ/p8_i2c.c
> > index 9e61e1fb5142..da39ea28df31 100644
> > --- a/drivers/hwmon/occ/p8_i2c.c
> > +++ b/drivers/hwmon/occ/p8_i2c.c
> > @@ -223,7 +223,7 @@ static int p8_i2c_occ_probe(struct i2c_client 
> > *client)
> >       occ->poll_cmd_data = 0x10;        /* P8 OCC poll data */
> >       occ->send_cmd = p8_i2c_occ_send_cmd;
> >   -    return occ_setup(occ, "p8_occ");
> > +    return occ_setup(occ);
> >   }
> >     static int p8_i2c_occ_remove(struct i2c_client *client)
> > diff --git a/drivers/hwmon/occ/p9_sbe.c b/drivers/hwmon/occ/p9_sbe.c
> > index 49b13cc01073..42fc7b97bb34 100644
> > --- a/drivers/hwmon/occ/p9_sbe.c
> > +++ b/drivers/hwmon/occ/p9_sbe.c
> > @@ -145,7 +145,7 @@ static int p9_sbe_occ_probe(struct 
> > platform_device *pdev)
> >       occ->poll_cmd_data = 0x20;        /* P9 OCC poll data */
> >       occ->send_cmd = p9_sbe_occ_send_cmd;
> >   -    rc = occ_setup(occ, "p9_occ");
> > +    rc = occ_setup(occ);
> >       if (rc == -ESHUTDOWN)
> >           rc = -ENODEV;    /* Host is shutdown, don't spew errors */
> >   diff --git a/drivers/hwmon/occ/sysfs.c b/drivers/hwmon/occ/sysfs.c
> > index b2f788a77746..2317301fc1e9 100644
> > --- a/drivers/hwmon/occ/sysfs.c
> > +++ b/drivers/hwmon/occ/sysfs.c
> > @@ -6,13 +6,13 @@
> >   #include <linux/export.h>
> >   #include <linux/hwmon-sysfs.h>
> >   #include <linux/kernel.h>
> > +#include <linux/kstrtox.h>
> >   #include <linux/sysfs.h>
> >     #include "common.h"
> >     /* OCC status register */
> >   #define OCC_STAT_MASTER            BIT(7)
> > -#define OCC_STAT_ACTIVE            BIT(0)
> >     /* OCC extended status register */
> >   #define OCC_EXT_STAT_DVFS_OT        BIT(7)
> > @@ -22,6 +22,25 @@
> >   #define OCC_EXT_STAT_DVFS_VDD        BIT(3)
> >   #define OCC_EXT_STAT_GPU_THROTTLE    GENMASK(2, 0)
> >   +static ssize_t occ_active_store(struct device *dev,
> > +                struct device_attribute *attr,
> > +                const char *buf, size_t count)
> > +{
> > +    int rc;
> > +    bool active;
> > +    struct occ *occ = dev_get_drvdata(dev);
> > +
> > +    rc = kstrtobool(buf, &active);
> > +    if (rc)
> > +        return rc;
> > +
> > +    rc = occ_active(occ, active);
> > +    if (rc)
> > +        return rc;
> > +
> > +    return count;
> > +}
> > +
> >   static ssize_t occ_sysfs_show(struct device *dev,
> >                     struct device_attribute *attr, char *buf)
> >   {
> > @@ -31,54 +50,64 @@ static ssize_t occ_sysfs_show(struct device *dev,
> >       struct occ_poll_response_header *header;
> >       struct sensor_device_attribute *sattr = to_sensor_dev_attr(attr);
> >   -    rc = occ_update_response(occ);
> > -    if (rc)
> > -        return rc;
> > +    if (occ->active) {
> > +        rc = occ_update_response(occ);
> > +        if (rc)
> > +            return rc;
> >   -    header = (struct occ_poll_response_header *)occ->resp.data;
> > -
> > -    switch (sattr->index) {
> > -    case 0:
> > -        val = !!(header->status & OCC_STAT_MASTER);
> > -        break;
> > -    case 1:
> > -        val = !!(header->status & OCC_STAT_ACTIVE);
> > -        break;
> > -    case 2:
> > -        val = !!(header->ext_status & OCC_EXT_STAT_DVFS_OT);
> > -        break;
> > -    case 3:
> > -        val = !!(header->ext_status & OCC_EXT_STAT_DVFS_POWER);
> > -        break;
> > -    case 4:
> > -        val = !!(header->ext_status & OCC_EXT_STAT_MEM_THROTTLE);
> > -        break;
> > -    case 5:
> > -        val = !!(header->ext_status & OCC_EXT_STAT_QUICK_DROP);
> > -        break;
> > -    case 6:
> > -        val = header->occ_state;
> > -        break;
> > -    case 7:
> > -        if (header->status & OCC_STAT_MASTER)
> > -            val = hweight8(header->occs_present);
> > -        else
> > +        header = (struct occ_poll_response_header *)occ->resp.data;
> > +
> > +        switch (sattr->index) {
> > +        case 0:
> > +            val = !!(header->status & OCC_STAT_MASTER);
> > +            break;
> > +        case 1:
> >               val = 1;
> > -        break;
> > -    case 8:
> > -        val = header->ips_status;
> > -        break;
> > -    case 9:
> > -        val = header->mode;
> > -        break;
> > -    case 10:
> > -        val = !!(header->ext_status & OCC_EXT_STAT_DVFS_VDD);
> > -        break;
> > -    case 11:
> > -        val = header->ext_status & OCC_EXT_STAT_GPU_THROTTLE;
> > -        break;
> > -    default:
> > -        return -EINVAL;
> > +            break;
> > +        case 2:
> > +            val = !!(header->ext_status & OCC_EXT_STAT_DVFS_OT);
> > +            break;
> > +        case 3:
> > +            val = !!(header->ext_status & OCC_EXT_STAT_DVFS_POWER);
> > +            break;
> > +        case 4:
> > +            val = !!(header->ext_status &
> > +                 OCC_EXT_STAT_MEM_THROTTLE);
> > +            break;
> > +        case 5:
> > +            val = !!(header->ext_status & OCC_EXT_STAT_QUICK_DROP);
> > +            break;
> > +        case 6:
> > +            val = header->occ_state;
> > +            break;
> > +        case 7:
> > +            if (header->status & OCC_STAT_MASTER)
> > +                val = hweight8(header->occs_present);
> > +            else
> > +                val = 1;
> > +            break;
> > +        case 8:
> > +            val = header->ips_status;
> > +            break;
> > +        case 9:
> > +            val = header->mode;
> > +            break;
> > +        case 10:
> > +            val = !!(header->ext_status & OCC_EXT_STAT_DVFS_VDD);
> > +            break;
> > +        case 11:
> > +            val = header->ext_status & OCC_EXT_STAT_GPU_THROTTLE;
> > +            break;
> > +        default:
> > +            return -EINVAL;
> > +        }
> > +    } else {
> > +        if (sattr->index == 1)
> > +            val = 0;
> > +        else if (sattr->index <= 11)
> > +            val = -ENODATA;
> > +        else
> > +            return -EINVAL;
> >       }
> >         return sysfs_emit(buf, "%d\n", val);
> > @@ -95,7 +124,8 @@ static ssize_t occ_error_show(struct device *dev,
> >   }
> >     static SENSOR_DEVICE_ATTR(occ_master, 0444, occ_sysfs_show, NULL, 
> > 0);
> > -static SENSOR_DEVICE_ATTR(occ_active, 0444, occ_sysfs_show, NULL, 1);
> > +static SENSOR_DEVICE_ATTR(occ_active, 0644, occ_sysfs_show, 
> > occ_active_store,
> > +              1);
> >   static SENSOR_DEVICE_ATTR(occ_dvfs_overtemp, 0444, occ_sysfs_show, 
> > NULL, 2);
> >   static SENSOR_DEVICE_ATTR(occ_dvfs_power, 0444, occ_sysfs_show, 
> > NULL, 3);
> >   static SENSOR_DEVICE_ATTR(occ_mem_throttle, 0444, occ_sysfs_show, 
> > NULL, 4);
> > @@ -139,7 +169,7 @@ void occ_sysfs_poll_done(struct occ *occ)
> >        * On the first poll response, we haven't yet created the sysfs
> >        * attributes, so don't make any notify calls.
> >        */
> > -    if (!occ->hwmon)
> > +    if (!occ->active)
> >           goto done;
> >         if ((header->status & OCC_STAT_MASTER) !=
> > @@ -148,12 +178,6 @@ void occ_sysfs_poll_done(struct occ *occ)
> >           sysfs_notify(&occ->bus_dev->kobj, NULL, name);
> >       }
> >   -    if ((header->status & OCC_STAT_ACTIVE) !=
> > -        (occ->prev_stat & OCC_STAT_ACTIVE)) {
> > -        name = sensor_dev_attr_occ_active.dev_attr.attr.name;
> > -        sysfs_notify(&occ->bus_dev->kobj, NULL, name);
> > -    }
> > -
> >       if ((header->ext_status & OCC_EXT_STAT_DVFS_OT) !=
> >           (occ->prev_ext_stat & OCC_EXT_STAT_DVFS_OT)) {
> >           name = sensor_dev_attr_occ_dvfs_overtemp.dev_attr.attr.name;
> > @@ -227,8 +251,7 @@ int occ_setup_sysfs(struct occ *occ)
> >       return sysfs_create_group(&occ->bus_dev->kobj, &occ_sysfs);
> >   }
> >   -void occ_shutdown(struct occ *occ)
> > +void occ_shutdown_sysfs(struct occ *occ)
> >   {
> >       sysfs_remove_group(&occ->bus_dev->kobj, &occ_sysfs);
> >   }
> > -EXPORT_SYMBOL_GPL(occ_shutdown);