[PATCH v2 07/10] drivers/hwmon/occ: Add error handling

[Eddie James]

From: "Edward A. James" 

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 
---
 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(6) /* 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(>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(_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(>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,
_dev_attr_occ_mem_throttle.dev_attr.attr,
_dev_attr_occ_quick_drop.dev_attr.attr,
_dev_attr_occ_status.dev_attr.attr,
+   _attr_occ_error.attr,
NULL
 };
 
@@ -1197,6 +1271,8 @@ int occ_setup(struct occ *occ, const char *name)
return rc;
}
 
+   atomic_inc(_present);
+
rc = sysfs_create_group(>bus_dev->kobj, _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(>bus_dev->kobj, _attr_group);
+
+   atomic_dec(_present);
 }
diff --git a/drivers/hwmon/occ/common.h 

[PATCH v2 07/10] drivers/hwmon/occ: Add error handling

[Eddie James]

From: "Edward A. James" 

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 
---
 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(6) /* 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(>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(_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(>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,
_dev_attr_occ_mem_throttle.dev_attr.attr,
_dev_attr_occ_quick_drop.dev_attr.attr,
_dev_attr_occ_status.dev_attr.attr,
+   _attr_occ_error.attr,
NULL
 };
 
@@ -1197,6 +1271,8 @@ int occ_setup(struct occ *occ, const char *name)
return rc;
}
 
+   atomic_inc(_present);
+
rc = sysfs_create_group(>bus_dev->kobj, _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(>bus_dev->kobj, _attr_group);
+
+   atomic_dec(_present);
 }
diff --git a/drivers/hwmon/occ/common.h b/drivers/hwmon/occ/common.h
index dc9e06d..cef2174