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Subject[PATCH v2 07/10] drivers/hwmon/occ: Add error handling
Date
From: "Edward A. James" <eajames@us.ibm.com>

Add logic to detect a number of error scenarios on the OCC. Export any
errors through an additional non-hwmon device attribute. The error
counting and state verification are required by the OCC hardware
specification.

Signed-off-by: Edward A. James <eajames@us.ibm.com>
---
drivers/hwmon/occ/common.c | 82 ++++++++++++++++++++++++++++++++++++++++++++--
drivers/hwmon/occ/common.h | 4 +++
2 files changed, 84 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/occ/common.c b/drivers/hwmon/occ/common.c
index 2459e12..970b31f 100644
--- a/drivers/hwmon/occ/common.c
+++ b/drivers/hwmon/occ/common.c
@@ -17,6 +17,11 @@

#include "common.h"

+#define OCC_ERROR_COUNT_THRESHOLD 2 /* OCC HW defined */
+
+#define OCC_STATE_SAFE 4
+#define OCC_SAFE_TIMEOUT msecs_to_jiffies(60000) /* 1 min */
+
#define OCC_UPDATE_FREQUENCY msecs_to_jiffies(1000)

/* OCC status bits */
@@ -126,10 +131,33 @@ struct extended_sensor {
u8 data[6];
} __packed;

+static atomic_t occs_present = ATOMIC_INIT(0);
+
+static ssize_t occ_show_error(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct occ *occ = dev_get_drvdata(dev);
+
+ return snprintf(buf, PAGE_SIZE - 1, "%d\n", occ->error);
+}
+
+static DEVICE_ATTR(occ_error, 0444, occ_show_error, NULL);
+
+/* Notify user if we have an error and a change in error state. */
+static void occ_notify_error(struct occ *occ, int old_error)
+{
+ /* check hwmon pointer to verify error attribute has been added */
+ if (occ->error != old_error && occ->error && occ->hwmon)
+ sysfs_notify(&occ->bus_dev->kobj, NULL,
+ dev_attr_occ_error.attr.name);
+}
+
static int occ_poll(struct occ *occ)
{
+ struct occ_poll_response_header *header;
u16 checksum = occ->poll_cmd_data + 1;
u8 cmd[8];
+ int rc, old_error = occ->error;

/* big endian */
cmd[0] = 0; /* sequence number */
@@ -142,12 +170,47 @@ static int occ_poll(struct occ *occ)
cmd[7] = 0;

/* mutex should already be locked if necessary */
- return occ->send_cmd(occ, cmd);
+ rc = occ->send_cmd(occ, cmd);
+ if (rc) {
+ if (occ->error_count++ > OCC_ERROR_COUNT_THRESHOLD)
+ occ->error = rc;
+
+ goto done;
+ }
+
+ /* clear error since communication was successful */
+ occ->error_count = 0;
+ occ->error = 0;
+
+ header = (struct occ_poll_response_header *)occ->resp.data;
+ /* check for safe state */
+ if (header->occ_state == OCC_STATE_SAFE) {
+ if (occ->last_safe) {
+ if (time_after(jiffies,
+ occ->last_safe + OCC_SAFE_TIMEOUT))
+ occ->error = -EHOSTDOWN;
+ } else {
+ occ->last_safe = jiffies;
+ }
+ } else {
+ occ->last_safe = 0;
+ }
+
+ if (header->status & OCC_STAT_MASTER) {
+ /* check if we're missing any OCCs */
+ if (hweight8(header->occs_present) !=
+ atomic_read(&occs_present))
+ occ->error = -ENXIO;
+ }
+
+done:
+ occ_notify_error(occ, old_error);
+ return rc;
}

static int occ_set_user_power_cap(struct occ *occ, u16 user_power_cap)
{
- int rc;
+ int rc, old_error = occ->error;
u8 cmd[8];
u16 checksum = 0x24;
__be16 user_power_cap_be = cpu_to_be16(user_power_cap);
@@ -171,6 +234,16 @@ static int occ_set_user_power_cap(struct occ *occ, u16 user_power_cap)

mutex_unlock(&occ->lock);

+ if (rc) {
+ if (occ->error_count++ > OCC_ERROR_COUNT_THRESHOLD)
+ occ->error = rc;
+ } else {
+ /* successful communication so clear the error */
+ occ->error_count = 0;
+ occ->error = 0;
+ }
+
+ occ_notify_error(occ, old_error);
return rc;
}

@@ -1110,6 +1183,7 @@ static ssize_t occ_show_status(struct device *dev,
&sensor_dev_attr_occ_mem_throttle.dev_attr.attr,
&sensor_dev_attr_occ_quick_drop.dev_attr.attr,
&sensor_dev_attr_occ_status.dev_attr.attr,
+ &dev_attr_occ_error.attr,
NULL
};

@@ -1197,6 +1271,8 @@ int occ_setup(struct occ *occ, const char *name)
return rc;
}

+ atomic_inc(&occs_present);
+
rc = sysfs_create_group(&occ->bus_dev->kobj, &occ_attr_group);
if (rc)
dev_warn(occ->bus_dev, "failed to create status attrs: %d\n",
@@ -1208,4 +1284,6 @@ int occ_setup(struct occ *occ, const char *name)
void occ_shutdown(struct occ *occ)
{
sysfs_remove_group(&occ->bus_dev->kobj, &occ_attr_group);
+
+ atomic_dec(&occs_present);
}
diff --git a/drivers/hwmon/occ/common.h b/drivers/hwmon/occ/common.h
index dc9e06d..cef2174 100644
--- a/drivers/hwmon/occ/common.h
+++ b/drivers/hwmon/occ/common.h
@@ -107,6 +107,10 @@ struct occ {
struct occ_attribute *attrs;
struct attribute_group group;
const struct attribute_group *groups[2];
+
+ int error;
+ unsigned int error_count; /* number of errors observed */
+ unsigned long last_safe; /* time OCC entered safe state */
};

int occ_setup(struct occ *occ, const char *name);
--
1.8.3.1
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