[PATCH platform-next v2 0/2] Support for handling interrupt storm

[PATCH platform-next v2 0/2] Support for handling interrupt storm

[Ciju Rajan K]

This patcheset contain:
 Patch #1 Add fields for interrupt storm handling
 Patch #2 Add support for handling interrupt storm

v0->v2

Comments pointed out by Ilpo:
- Renamed the macro MLXREG_HOTPLUG_WM_WINDOW to MLXREG_HOTPLUG_WM_WINDOW_MS to indicate milli seconds
- Removed the timestamp stored in wmark_high_ts and used jiffies directly
- Calculating the time window and storing it in the new variable wmark_window.
- Removed the variables wmark_low_ts and wmark_high_ts
- Used continue statement inside the time window check

Changes added by Ciju:
- Renamed variable wmark_low_cntr to wmark_cntr
- Fixed the time window to check for interrupt storm

Ciju Rajan K (2):
  platform_data/mlxreg: Add fields for interrupt storm handling
  platform/mellanox: mlxreg-hotplug: Add support for handling interrupt
    storm

 drivers/platform/mellanox/mlxreg-hotplug.c | 32 ++++++++++++++++++++--
 include/linux/platform_data/mlxreg.h       |  6 ++++
 2 files changed, 36 insertions(+), 2 deletions(-)

-- 
2.47.2

[PATCH platform-next v2 1/2] [PATCH platform-next 1/2] platform_data/mlxreg: Add fields for interrupt storm handling

[Ciju Rajan K]

Add fields for interrupt storm handling.
Extend structure mlxreg_core_data with the following fields:
 'wmark_cntr'   - interrupt storm counter.
 'wmark_window' - time window to count interrupts to check for storm.

Extend structure mlxreg_core_item with the following field:
 'storming_bits' - interrupt storming bits mask.

Reviewed-by: Vadim Pasternak <vadimp@nvidia.com>
Signed-off-by: Ciju Rajan K <crajank@nvidia.com>
---
 include/linux/platform_data/mlxreg.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/linux/platform_data/mlxreg.h b/include/linux/platform_data/mlxreg.h
index f6cca7a035c7..453c8dfd7eb9 100644
--- a/include/linux/platform_data/mlxreg.h
+++ b/include/linux/platform_data/mlxreg.h
@@ -131,6 +131,8 @@ struct mlxreg_hotplug_device {
  * @regnum: number of registers occupied by multi-register attribute;
  * @slot: slot number, at which device is located;
  * @secured: if set indicates that entry access is secured;
+ * @wmark_cntr: interrupt storm counter;
+ * @wmark_window: time window to count interrupts to check for storm;
  */
 struct mlxreg_core_data {
 	char label[MLXREG_CORE_LABEL_MAX_SIZE];
@@ -151,6 +153,8 @@ struct mlxreg_core_data {
 	u8 regnum;
 	u8 slot;
 	u8 secured;
+	unsigned int wmark_cntr;
+	unsigned long wmark_window;
 };
 
 /**
@@ -167,6 +171,7 @@ struct mlxreg_core_data {
  * @ind: element's index inside the group;
  * @inversed: if 0: 0 for signal status is OK, if 1 - 1 is OK;
  * @health: true if device has health indication, false in other case;
+ * @storming_bits: interrupt storming bits mask;
  */
 struct mlxreg_core_item {
 	struct mlxreg_core_data *data;
@@ -180,6 +185,7 @@ struct mlxreg_core_item {
 	u8 ind;
 	u8 inversed;
 	u8 health;
+	u32 storming_bits;
 };
 
 /**
-- 
2.47.2

Re: [PATCH platform-next v2 1/2] [PATCH platform-next 1/2] platform_data/mlxreg: Add fields for interrupt storm handling

[Ilpo Järvinen]

On Tue, 23 Sep 2025, Ciju Rajan K wrote:

> Add fields for interrupt storm handling.
> Extend structure mlxreg_core_data with the following fields:
>  'wmark_cntr'   - interrupt storm counter.
>  'wmark_window' - time window to count interrupts to check for storm.
> 
> Extend structure mlxreg_core_item with the following field:
>  'storming_bits' - interrupt storming bits mask.
> 
> Reviewed-by: Vadim Pasternak <vadimp@nvidia.com>
> Signed-off-by: Ciju Rajan K <crajank@nvidia.com>
> ---
>  include/linux/platform_data/mlxreg.h | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/include/linux/platform_data/mlxreg.h b/include/linux/platform_data/mlxreg.h
> index f6cca7a035c7..453c8dfd7eb9 100644
> --- a/include/linux/platform_data/mlxreg.h
> +++ b/include/linux/platform_data/mlxreg.h
> @@ -131,6 +131,8 @@ struct mlxreg_hotplug_device {
>   * @regnum: number of registers occupied by multi-register attribute;
>   * @slot: slot number, at which device is located;
>   * @secured: if set indicates that entry access is secured;
> + * @wmark_cntr: interrupt storm counter;
> + * @wmark_window: time window to count interrupts to check for storm;
>   */
>  struct mlxreg_core_data {
>  	char label[MLXREG_CORE_LABEL_MAX_SIZE];
> @@ -151,6 +153,8 @@ struct mlxreg_core_data {
>  	u8 regnum;
>  	u8 slot;
>  	u8 secured;
> +	unsigned int wmark_cntr;
> +	unsigned long wmark_window;
>  };
>  
>  /**
> @@ -167,6 +171,7 @@ struct mlxreg_core_data {
>   * @ind: element's index inside the group;
>   * @inversed: if 0: 0 for signal status is OK, if 1 - 1 is OK;
>   * @health: true if device has health indication, false in other case;
> + * @storming_bits: interrupt storming bits mask;
>   */
>  struct mlxreg_core_item {
>  	struct mlxreg_core_data *data;
> @@ -180,6 +185,7 @@ struct mlxreg_core_item {
>  	u8 ind;
>  	u8 inversed;
>  	u8 health;
> +	u32 storming_bits;
>  };
>  
>  /**
> 

I don't know what's the benefit of having this as a separate patch, the 
fields are getting used in patch 2 so it would feel natural to introduce 
them there so the entire change would end up into the same commit.

-- 
 i.

RE: [PATCH platform-next v2 1/2] [PATCH platform-next 1/2] platform_data/mlxreg: Add fields for interrupt storm handling

[Ciju Rajan K]

Hi Ilpo,

Thanks for the review.

> >  struct mlxreg_core_item {
> >       struct mlxreg_core_data *data;
> > @@ -180,6 +185,7 @@ struct mlxreg_core_item {
> >       u8 ind;
> >       u8 inversed;
> >       u8 health;
> > +     u32 storming_bits;
> >  };
> >
> >  /**
> >
> 
> I don't know what's the benefit of having this as a separate patch, the
> fields are getting used in patch 2 so it would feel natural to introduce
> them there so the entire change would end up into the same commit.

Combined into a single patch.

Thanks
Ciju

[PATCH platform-next v2 2/2] [PATCH platform-next 2/2] platform/mellanox: mlxreg-hotplug: Add support for handling interrupt storm

[Ciju Rajan K]

In case of broken hardware, it is possible that broken device will
flood interrupt handler with false events. For example, if fan or
power supply has damaged presence pin, it will cause permanent
generation of plugged in / plugged out events. As a result, interrupt
handler will consume a lot of CPU resources and will keep raising
"UDEV" events to the user space.

This patch provides a mechanism to detect device causing interrupt
flooding and mask interrupt for this specific device, to isolate
from interrupt handling flow. Use the following criteria: if the
specific interrupt was generated 'N' times during 'T' seconds,
such device is to be considered as broken and will be closed for
getting interrupts. User will be notified through the log error
and will be instructed to replace broken device.

Reviewed-by: Vadim Pasternak <vadimp@nvidia.com>
Signed-off-by: Ciju Rajan K <crajank@nvidia.com>
---
 drivers/platform/mellanox/mlxreg-hotplug.c | 32 ++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/drivers/platform/mellanox/mlxreg-hotplug.c b/drivers/platform/mellanox/mlxreg-hotplug.c
index d246772aafd6..ae0115ea1fd1 100644
--- a/drivers/platform/mellanox/mlxreg-hotplug.c
+++ b/drivers/platform/mellanox/mlxreg-hotplug.c
@@ -11,6 +11,7 @@
 #include <linux/hwmon-sysfs.h>
 #include <linux/i2c.h>
 #include <linux/interrupt.h>
+#include <linux/jiffies.h>
 #include <linux/module.h>
 #include <linux/platform_data/mlxreg.h>
 #include <linux/platform_device.h>
@@ -30,6 +31,11 @@
 #define MLXREG_HOTPLUG_ATTRS_MAX	128
 #define MLXREG_HOTPLUG_NOT_ASSERT	3
 
+/* Interrupt storm definitions */
+#define MLXREG_HOTPLUG_WM_COUNTER	100
+/* Time window in milliseconds */
+#define MLXREG_HOTPLUG_WM_WINDOW_MS	3000
+
 /**
  * struct mlxreg_hotplug_priv_data - platform private data:
  * @irq: platform device interrupt number;
@@ -366,11 +372,33 @@ mlxreg_hotplug_work_helper(struct mlxreg_hotplug_priv_data *priv,
 	for_each_set_bit(bit, &asserted, 8) {
 		int pos;
 
+		/* Skip already marked storming bit. */
+		if (item->storming_bits & BIT(bit))
+			continue;
+
 		pos = mlxreg_hotplug_item_label_index_get(item->mask, bit);
 		if (pos < 0)
 			goto out;
 
 		data = item->data + pos;
+
+		/* Interrupt storm handling logic. */
+		if (data->wmark_cntr == 0)
+			data->wmark_window = jiffies +
+				msecs_to_jiffies(MLXREG_HOTPLUG_WM_WINDOW_MS);
+
+		if (data->wmark_cntr >= MLXREG_HOTPLUG_WM_COUNTER - 1) {
+			if (time_after(data->wmark_window, jiffies)) {
+				dev_err(priv->dev,
+					"Storming bit %d (label: %s) - interrupt masked permanently. Replace broken HW.",
+					bit, data->label);
+				/* Mark bit as storming. */
+				item->storming_bits |= BIT(bit);
+				continue;
+			}
+			data->wmark_cntr = 0;
+		}
+		data->wmark_cntr++;
 		if (regval & BIT(bit)) {
 			if (item->inversed)
 				mlxreg_hotplug_device_destroy(priv, data, item->kind);
@@ -390,9 +418,9 @@ mlxreg_hotplug_work_helper(struct mlxreg_hotplug_priv_data *priv,
 	if (ret)
 		goto out;
 
-	/* Unmask event. */
+	/* Unmask event, exclude storming bits. */
 	ret = regmap_write(priv->regmap, item->reg + MLXREG_HOTPLUG_MASK_OFF,
-			   item->mask);
+			   item->mask & ~item->storming_bits);
 
  out:
 	if (ret)
-- 
2.47.2

Re: [PATCH platform-next v2 2/2] [PATCH platform-next 2/2] platform/mellanox: mlxreg-hotplug: Add support for handling interrupt storm

[Ilpo Järvinen]

On Tue, 23 Sep 2025, Ciju Rajan K wrote:

> In case of broken hardware, it is possible that broken device will
> flood interrupt handler with false events. For example, if fan or
> power supply has damaged presence pin, it will cause permanent
> generation of plugged in / plugged out events. As a result, interrupt
> handler will consume a lot of CPU resources and will keep raising
> "UDEV" events to the user space.
> 
> This patch provides a mechanism to detect device causing interrupt
> flooding and mask interrupt for this specific device, to isolate
> from interrupt handling flow. Use the following criteria: if the
> specific interrupt was generated 'N' times during 'T' seconds,
> such device is to be considered as broken and will be closed for
> getting interrupts. User will be notified through the log error
> and will be instructed to replace broken device.
> 
> Reviewed-by: Vadim Pasternak <vadimp@nvidia.com>
> Signed-off-by: Ciju Rajan K <crajank@nvidia.com>
> ---
>  drivers/platform/mellanox/mlxreg-hotplug.c | 32 ++++++++++++++++++++--
>  1 file changed, 30 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/platform/mellanox/mlxreg-hotplug.c b/drivers/platform/mellanox/mlxreg-hotplug.c
> index d246772aafd6..ae0115ea1fd1 100644
> --- a/drivers/platform/mellanox/mlxreg-hotplug.c
> +++ b/drivers/platform/mellanox/mlxreg-hotplug.c
> @@ -11,6 +11,7 @@
>  #include <linux/hwmon-sysfs.h>
>  #include <linux/i2c.h>
>  #include <linux/interrupt.h>
> +#include <linux/jiffies.h>
>  #include <linux/module.h>
>  #include <linux/platform_data/mlxreg.h>
>  #include <linux/platform_device.h>
> @@ -30,6 +31,11 @@
>  #define MLXREG_HOTPLUG_ATTRS_MAX	128
>  #define MLXREG_HOTPLUG_NOT_ASSERT	3
>  
> +/* Interrupt storm definitions */
> +#define MLXREG_HOTPLUG_WM_COUNTER	100
> +/* Time window in milliseconds */
> +#define MLXREG_HOTPLUG_WM_WINDOW_MS	3000
> +
>  /**
>   * struct mlxreg_hotplug_priv_data - platform private data:
>   * @irq: platform device interrupt number;
> @@ -366,11 +372,33 @@ mlxreg_hotplug_work_helper(struct mlxreg_hotplug_priv_data *priv,
>  	for_each_set_bit(bit, &asserted, 8) {
>  		int pos;
>  
> +		/* Skip already marked storming bit. */
> +		if (item->storming_bits & BIT(bit))
> +			continue;
> +
>  		pos = mlxreg_hotplug_item_label_index_get(item->mask, bit);
>  		if (pos < 0)
>  			goto out;
>  
>  		data = item->data + pos;
> +
> +		/* Interrupt storm handling logic. */
> +		if (data->wmark_cntr == 0)
> +			data->wmark_window = jiffies +
> +				msecs_to_jiffies(MLXREG_HOTPLUG_WM_WINDOW_MS);

Please use braces for multi-line if blocks.

> +
> +		if (data->wmark_cntr >= MLXREG_HOTPLUG_WM_COUNTER - 1) {
> +			if (time_after(data->wmark_window, jiffies)) {
> +				dev_err(priv->dev,
> +					"Storming bit %d (label: %s) - interrupt masked permanently. Replace broken HW.",
> +					bit, data->label);
> +				/* Mark bit as storming. */
> +				item->storming_bits |= BIT(bit);
> +				continue;
> +			}
> +			data->wmark_cntr = 0;
> +		}
> +		data->wmark_cntr++;

I think this should be in else block to allow recalculation of the time 
window when the counter wraps.

>  		if (regval & BIT(bit)) {
>  			if (item->inversed)
>  				mlxreg_hotplug_device_destroy(priv, data, item->kind);
> @@ -390,9 +418,9 @@ mlxreg_hotplug_work_helper(struct mlxreg_hotplug_priv_data *priv,
>  	if (ret)
>  		goto out;
>  
> -	/* Unmask event. */
> +	/* Unmask event, exclude storming bits. */
>  	ret = regmap_write(priv->regmap, item->reg + MLXREG_HOTPLUG_MASK_OFF,
> -			   item->mask);
> +			   item->mask & ~item->storming_bits);
>  
>   out:
>  	if (ret)
> 

-- 
 i.

RE: [PATCH platform-next v2 2/2] [PATCH platform-next 2/2] platform/mellanox: mlxreg-hotplug: Add support for handling interrupt storm

[Ciju Rajan K]

Hi Ilpo,

Thanks for the review.

> > +
> > +             /* Interrupt storm handling logic. */
> > +             if (data->wmark_cntr == 0)
> > +                     data->wmark_window = jiffies +
> > +
> msecs_to_jiffies(MLXREG_HOTPLUG_WM_WINDOW_MS);
> 
> Please use braces for multi-line if blocks.

Done. 

> > +
> > +             if (data->wmark_cntr >= MLXREG_HOTPLUG_WM_COUNTER - 1) {
> > +                     if (time_after(data->wmark_window, jiffies)) {
> > +                             dev_err(priv->dev,
> > +                                     "Storming bit %d (label: %s) - interrupt masked
> permanently. Replace broken HW.",
> > +                                     bit, data->label);
> > +                             /* Mark bit as storming. */
> > +                             item->storming_bits |= BIT(bit);
> > +                             continue;
> > +                     }
> > +                     data->wmark_cntr = 0;
> > +             }
> > +             data->wmark_cntr++;
> 
> I think this should be in else block to allow recalculation of the time
> window when the counter wraps.

Good catch. Otherwise, time window will never get reset. Fixed in the next version (on the way).

Thanks
Ciju