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Date: Fri, 29 Apr 2022 07:13:12 +0000
From: Joel Stanley <joel@....id.au>
To: Guenter Roeck <linux@...ck-us.net>
Cc: Eddie James <eajames@...ux.ibm.com>, linux-hwmon@...r.kernel.org,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Jean Delvare <jdelvare@...e.com>
Subject: Re: [PATCH v2] hwmon (occ): Delay hwmon registration until user request
On Wed, 27 Apr 2022 at 14:34, Guenter Roeck <linux@...ck-us.net> wrote:
>
> On Wed, Apr 27, 2022 at 09:04:43AM -0500, Eddie James wrote:
> > Instead of registering the hwmon device at probe time, use the
> > existing "occ_active" sysfs file to control when the driver polls
> > the OCC for sensor data and registers with hwmon. 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, resulting in
> > unrecoverable system errors.
> >
> > Signed-off-by: Eddie James <eajames@...ux.ibm.com>
>
> Applied to hwmon-next.
Will this change break existing userspace? As I understand it existing
systems rely on the driver probing for the occ without extra
interaction.
>From your commit message, it sounds like we should inhibit SBE
communication during the sensitive period. This would stop any
devices, not just the OCC, from generating unwanted traffic.
>
> Guenter
>
> > ---
> > Changes since v1:
> > - Update commit message to for clarity.
> >
> > 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@...ux.ibm.com>");
> > 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);
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