perf/arm-cmn: Fix wp_dev_sel2 setting for multi-DTM configurations

[PATCH v2] perf/arm-cmn: Fix wp_dev_sel2 setting for multi-DTM configurations

Posted by Shouping Wang 2 weeks, 1 day ago

When MXP_MULTIPLE_DTM_EN is TRUE, each DTM will monitor at most
two device ports. In this case, {wp_dev_sel2, wp_dev_sel} will
only use values 2'b00 and 2'b01 per DTM.

Previously the setting allowed values beyond the supported range
per DTM, which could cause each DTM to select invalid ports when
MXP_MULTIPLE_DTM_EN is TRUE.

Fix this by only setting CMN_DTM_WPn_CONFIG_WP_DEV_SEL2 when
!multi_dtm.

Fixes: 60d1504070c2 ("perf/arm-cmn: Support new IP features")
Signed-off-by: Shouping Wang <allen.wang@hj-micro.com>
---

Changes in v2:
- Made the setting of CMN_DTM_WPn_CONFIG_WP_DEV_SEL2 conditional on
  !multi_dtm, instead of clamping with dev %= 2.
- Refactored is_cmn600 to use cmn->part directly.
- Updated the commit message.

Link to v1: https://lore.kernel.org/lkml/20260819105443.668784-1-allen.wang@hj-micro.com/

 drivers/perf/arm-cmn.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
index 6e5cc4086a9e..7e7590381171 100644
--- a/drivers/perf/arm-cmn.c
+++ b/drivers/perf/arm-cmn.c
@@ -1393,13 +1393,14 @@ static void arm_cmn_claim_wp_idx(struct arm_cmn_dtm *dtm,
 
 static u32 arm_cmn_wp_config(struct perf_event *event, int wp_idx)
 {
+	struct arm_cmn *cmn = to_cmn(event->pmu);
 	u32 config;
 	u32 dev = CMN_EVENT_WP_DEV_SEL(event);
 	u32 chn = CMN_EVENT_WP_CHN_SEL(event);
 	u32 grp = CMN_EVENT_WP_GRP(event);
 	u32 exc = CMN_EVENT_WP_EXCLUSIVE(event);
 	u32 combine = CMN_EVENT_WP_COMBINE(event);
-	bool is_cmn600 = to_cmn(event->pmu)->part == PART_CMN600;
+	bool is_cmn600 = cmn->part == PART_CMN600;
 
 	/* CMN-600 supports only primary and secondary matching groups */
 	if (is_cmn600)
@@ -1407,8 +1408,11 @@ static u32 arm_cmn_wp_config(struct perf_event *event, int wp_idx)
 
 	config = FIELD_PREP(CMN_DTM_WPn_CONFIG_WP_DEV_SEL, dev) |
 		 FIELD_PREP(CMN_DTM_WPn_CONFIG_WP_CHN_SEL, chn) |
-		 FIELD_PREP(CMN_DTM_WPn_CONFIG_WP_GRP, grp) |
-		 FIELD_PREP(CMN_DTM_WPn_CONFIG_WP_DEV_SEL2, dev >> 1);
+		 FIELD_PREP(CMN_DTM_WPn_CONFIG_WP_GRP, grp);
+
+	if (!cmn->multi_dtm)
+		config |= FIELD_PREP(CMN_DTM_WPn_CONFIG_WP_DEV_SEL2, dev >> 1);
+
 	if (exc)
 		config |= is_cmn600 ? CMN600_WPn_CONFIG_WP_EXCLUSIVE :
 				      CMN_DTM_WPn_CONFIG_WP_EXCLUSIVE;
-- 
2.43.0

Re: [PATCH v2] perf/arm-cmn: Fix wp_dev_sel2 setting for multi-DTM configurations

Posted by Will Deacon 2 weeks ago

On Thu, 10 Sep 2026 19:46:01 +0800, Shouping Wang wrote:
> When MXP_MULTIPLE_DTM_EN is TRUE, each DTM will monitor at most
> two device ports. In this case, {wp_dev_sel2, wp_dev_sel} will
> only use values 2'b00 and 2'b01 per DTM.
> 
> Previously the setting allowed values beyond the supported range
> per DTM, which could cause each DTM to select invalid ports when
> MXP_MULTIPLE_DTM_EN is TRUE.
> 
> [...]

Applied to arm64 (for-next/fixes), thanks!

[1/1] perf/arm-cmn: Fix wp_dev_sel2 setting for multi-DTM configurations
      https://git.kernel.org/arm64/c/49daa3d668b6

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev

Re: [PATCH v2] perf/arm-cmn: Fix wp_dev_sel2 setting for multi-DTM configurations

Posted by Robin Murphy 2 weeks, 1 day ago

On 10/09/2026 12:46 pm, Shouping Wang wrote:
> When MXP_MULTIPLE_DTM_EN is TRUE, each DTM will monitor at most
> two device ports. In this case, {wp_dev_sel2, wp_dev_sel} will
> only use values 2'b00 and 2'b01 per DTM.

Poor documentation strikes again!

> Previously the setting allowed values beyond the supported range
> per DTM, which could cause each DTM to select invalid ports when
> MXP_MULTIPLE_DTM_EN is TRUE.
> 
> Fix this by only setting CMN_DTM_WPn_CONFIG_WP_DEV_SEL2 when
> !multi_dtm.

Reviewed-by: Robin Murphy <robin.murphy@arm.com>

Thanks for the fix!
Robin.

> Fixes: 60d1504070c2 ("perf/arm-cmn: Support new IP features")
> Signed-off-by: Shouping Wang <allen.wang@hj-micro.com>
> ---
> 
> Changes in v2:
> - Made the setting of CMN_DTM_WPn_CONFIG_WP_DEV_SEL2 conditional on
>    !multi_dtm, instead of clamping with dev %= 2.
> - Refactored is_cmn600 to use cmn->part directly.
> - Updated the commit message.
> 
> Link to v1: https://lore.kernel.org/lkml/20260819105443.668784-1-allen.wang@hj-micro.com/
> 
>   drivers/perf/arm-cmn.c | 10 +++++++---
>   1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
> index 6e5cc4086a9e..7e7590381171 100644
> --- a/drivers/perf/arm-cmn.c
> +++ b/drivers/perf/arm-cmn.c
> @@ -1393,13 +1393,14 @@ static void arm_cmn_claim_wp_idx(struct arm_cmn_dtm *dtm,
>   
>   static u32 arm_cmn_wp_config(struct perf_event *event, int wp_idx)
>   {
> +	struct arm_cmn *cmn = to_cmn(event->pmu);
>   	u32 config;
>   	u32 dev = CMN_EVENT_WP_DEV_SEL(event);
>   	u32 chn = CMN_EVENT_WP_CHN_SEL(event);
>   	u32 grp = CMN_EVENT_WP_GRP(event);
>   	u32 exc = CMN_EVENT_WP_EXCLUSIVE(event);
>   	u32 combine = CMN_EVENT_WP_COMBINE(event);
> -	bool is_cmn600 = to_cmn(event->pmu)->part == PART_CMN600;
> +	bool is_cmn600 = cmn->part == PART_CMN600;
>   
>   	/* CMN-600 supports only primary and secondary matching groups */
>   	if (is_cmn600)
> @@ -1407,8 +1408,11 @@ static u32 arm_cmn_wp_config(struct perf_event *event, int wp_idx)
>   
>   	config = FIELD_PREP(CMN_DTM_WPn_CONFIG_WP_DEV_SEL, dev) |
>   		 FIELD_PREP(CMN_DTM_WPn_CONFIG_WP_CHN_SEL, chn) |
> -		 FIELD_PREP(CMN_DTM_WPn_CONFIG_WP_GRP, grp) |
> -		 FIELD_PREP(CMN_DTM_WPn_CONFIG_WP_DEV_SEL2, dev >> 1);
> +		 FIELD_PREP(CMN_DTM_WPn_CONFIG_WP_GRP, grp);
> +
> +	if (!cmn->multi_dtm)
> +		config |= FIELD_PREP(CMN_DTM_WPn_CONFIG_WP_DEV_SEL2, dev >> 1);
> +
>   	if (exc)
>   		config |= is_cmn600 ? CMN600_WPn_CONFIG_WP_EXCLUSIVE :
>   				      CMN_DTM_WPn_CONFIG_WP_EXCLUSIVE;