Re: [PATCH v3] soc: qcom: icc-bwmon: Update zone1_thres_count to 3

[Dmitry Baryshkov]

On Fri, Feb 27, 2026 at 04:40:51PM +0530, Pushpendra Singh wrote:
> From: Shivnandan Kumar <quic_kshivnan@xxxxxxxxxxx>
> 
> Reduce zone1_thres_count from 16 to 3 so the driver can lower the bus
> vote after 3 sample windows instead of waiting for 16. The previous
> 16‑window delay (~64 ms) is too long at higher FPS workloads,
> causing delayed decision making and measurable power regression.
> 
> Empirical tuning showed that lower values (e.g., 2) made bwmon behavior
> jittery, while higher values (4–6) were stable but less responsive and
> reduced power savings. A value of 3 provided the best balance: responsive
> enough for timely power reduction while maintaining stable bwmon
> operation.

Can you please justify this somehow? Numbers? Just the intuition?

> 
> Significant power savings were observed across multiple use cases when
> reducing the threshold from 16 to 3:
> 
> USECASE			zone1_thres_count=16     zone1_thres_count=3
> 4K video playback	   236.15 mA                  203.15 mA
> Sleep			    7mA			        6.9mA
> Display (idle display)	  71.95mA			67.11mA
> 
> Signed-off-by: Shivnandan Kumar <quic_kshivnan@xxxxxxxxxxx>
> Signed-off-by: Pushpendra Singh <pussin@xxxxxxxxxxxxxxxx>
> ---
> Chages in v3:
> - Update commit message
> - Link to v2: https://lore.kernel.org/lkml/d72182bc-f8d4-4314-b2f1-c9242618eb67@xxxxxxxxxxx/
> 
> Changes in v2:
> - Update commit message
> - Link to v1: https://lore.kernel.org/lkml/463eb7c8-00fc-4441-91d1-6e48f6b052c8@xxxxxxxxxxx
> ---
>  drivers/soc/qcom/icc-bwmon.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/soc/qcom/icc-bwmon.c b/drivers/soc/qcom/icc-bwmon.c
> index 597f9025e422..e46975da7dba 100644
> --- a/drivers/soc/qcom/icc-bwmon.c
> +++ b/drivers/soc/qcom/icc-bwmon.c
> @@ -830,7 +830,7 @@ static const struct icc_bwmon_data msm8998_bwmon_data = {
>  static const struct icc_bwmon_data sdm845_cpu_bwmon_data = {
>  	.sample_ms = 4,
>  	.count_unit_kb = 64,
> -	.zone1_thres_count = 16,
> +	.zone1_thres_count = 3,
>  	.zone3_thres_count = 1,
>  	.quirks = BWMON_HAS_GLOBAL_IRQ,
>  	.regmap_fields = sdm845_cpu_bwmon_reg_fields,
> @@ -849,7 +849,7 @@ static const struct icc_bwmon_data sdm845_llcc_bwmon_data = {
>  static const struct icc_bwmon_data sc7280_llcc_bwmon_data = {
>  	.sample_ms = 4,
>  	.count_unit_kb = 64,
> -	.zone1_thres_count = 16,
> +	.zone1_thres_count = 3,
>  	.zone3_thres_count = 1,
>  	.quirks = BWMON_NEEDS_FORCE_CLEAR,
>  	.regmap_fields = sdm845_llcc_bwmon_reg_fields,
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry