[PATCH] hwmon: (occ) Fix poll rate limiting

[PATCH] hwmon: (occ) Fix poll rate limiting

[Eddie James]

The poll rate limiter time was initialized at zero. This breaks the
comparison in time_after if jiffies is large. Switch to storing the
next update time rather than the previous time, and initialize the
time when the device is probed.

Fixes: c10e753d43eb ("hwmon (occ): Add sensor types and versions")
Signed-off-by: Eddie James <eajames@linux.ibm.com>
---
 drivers/hwmon/occ/common.c | 5 +++--
 drivers/hwmon/occ/common.h | 2 +-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/occ/common.c b/drivers/hwmon/occ/common.c
index f1ac153d0b56..967532afb1c0 100644
--- a/drivers/hwmon/occ/common.c
+++ b/drivers/hwmon/occ/common.c
@@ -217,9 +217,9 @@ int occ_update_response(struct occ *occ)
 		return rc;
 
 	/* limit the maximum rate of polling the OCC */
-	if (time_after(jiffies, occ->last_update + OCC_UPDATE_FREQUENCY)) {
+	if (time_after(jiffies, occ->next_update)) {
 		rc = occ_poll(occ);
-		occ->last_update = jiffies;
+		occ->next_update = jiffies + OCC_UPDATE_FREQUENCY;
 	} else {
 		rc = occ->last_error;
 	}
@@ -1165,6 +1165,7 @@ int occ_setup(struct occ *occ, const char *name)
 		return rc;
 	}
 
+	occ->next_update = jiffies + OCC_UPDATE_FREQUENCY;
 	occ_parse_poll_response(occ);
 
 	rc = occ_setup_sensor_attrs(occ);
diff --git a/drivers/hwmon/occ/common.h b/drivers/hwmon/occ/common.h
index 67e6968b8978..e6df719770e8 100644
--- a/drivers/hwmon/occ/common.h
+++ b/drivers/hwmon/occ/common.h
@@ -99,7 +99,7 @@ struct occ {
 	u8 poll_cmd_data;		/* to perform OCC poll command */
 	int (*send_cmd)(struct occ *occ, u8 *cmd);
 
-	unsigned long last_update;
+	unsigned long next_update;
 	struct mutex lock;		/* lock OCC access */
 
 	struct device *hwmon;
-- 
2.27.0

Re: [PATCH] hwmon: (occ) Fix poll rate limiting

[Guenter Roeck]

On Thu, Apr 29, 2021 at 10:13:36AM -0500, Eddie James wrote:
> The poll rate limiter time was initialized at zero. This breaks the
> comparison in time_after if jiffies is large. Switch to storing the
> next update time rather than the previous time, and initialize the
> time when the device is probed.
> 
> Fixes: c10e753d43eb ("hwmon (occ): Add sensor types and versions")
> Signed-off-by: Eddie James <eajames@linux.ibm.com>

Applied.

Thanks,
Guenter

> ---
>  drivers/hwmon/occ/common.c | 5 +++--
>  drivers/hwmon/occ/common.h | 2 +-
>  2 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/hwmon/occ/common.c b/drivers/hwmon/occ/common.c
> index f1ac153d0b56..967532afb1c0 100644
> --- a/drivers/hwmon/occ/common.c
> +++ b/drivers/hwmon/occ/common.c
> @@ -217,9 +217,9 @@ int occ_update_response(struct occ *occ)
>  		return rc;
>  
>  	/* limit the maximum rate of polling the OCC */
> -	if (time_after(jiffies, occ->last_update + OCC_UPDATE_FREQUENCY)) {
> +	if (time_after(jiffies, occ->next_update)) {
>  		rc = occ_poll(occ);
> -		occ->last_update = jiffies;
> +		occ->next_update = jiffies + OCC_UPDATE_FREQUENCY;
>  	} else {
>  		rc = occ->last_error;
>  	}
> @@ -1165,6 +1165,7 @@ int occ_setup(struct occ *occ, const char *name)
>  		return rc;
>  	}
>  
> +	occ->next_update = jiffies + OCC_UPDATE_FREQUENCY;
>  	occ_parse_poll_response(occ);
>  
>  	rc = occ_setup_sensor_attrs(occ);
> diff --git a/drivers/hwmon/occ/common.h b/drivers/hwmon/occ/common.h
> index 67e6968b8978..e6df719770e8 100644
> --- a/drivers/hwmon/occ/common.h
> +++ b/drivers/hwmon/occ/common.h
> @@ -99,7 +99,7 @@ struct occ {
>  	u8 poll_cmd_data;		/* to perform OCC poll command */
>  	int (*send_cmd)(struct occ *occ, u8 *cmd);
>  
> -	unsigned long last_update;
> +	unsigned long next_update;
>  	struct mutex lock;		/* lock OCC access */
>  
>  	struct device *hwmon;