Re: [BUG] ideapad_laptop: fans do not ramp up properly under CPU load on Lenovo IdeaPad 3 15ALC6 Ub (82KU)

[Sourajyoti Basak <basak.sb2006@gmail.com>]

On 09/05/26 9:00 pm, Sourajyoti Basak wrote:
> Hello,
> 
> I am using a Lenovo IdeaPad 3 15ALC6 Ub (82KU), and I am encountering an
> issue where the laptop fans do not respond appropriately to increasing
> CPU temperatures under Linux.
> 
> System information:
> Laptop: Lenovo IdeaPad 3 15ALC6 Ub
> BIOS version:GLCN46WW
> System performance mode in BIOS: Extreme Performance
> Kernel: Linux 7.0.5-1-cachyos
> Distribution: CachyOS
> CPU: AMD Ryzen 5 5500U (12) @ 4.06 GHz
> 
> Issue description:
> Under sustained CPU load (for example using stress -c $(nproc)), CPU
> temperatures rapidly increase to around 95-100°C. However, the fans do
> not ramp to maximum speed as expected. Therefore, the system begins
> thermal throttling after some time in this state.
> 
> As a result:
> 
> - The CPU reaches thermal throttling temperatures.
> - CPU frequencies drop significantly once throttling begins.
> - Fan RPM appears capped or insufficient despite high temperatures.
> - The issue appears consistently reproducible on my laptop and another
>   person's laptop.
> 
> Additional observations:
> 
> - The issue persists across multiple recent kernel versions.
> - No hardware issues appear to be present. (Verified that the fans can
> indeed
>   ramp up to max speed by 
> `echo 1 | sudo tee /sys/bus/platform/drivers/ideapad_acpi/VPC2004:00/
> fan_mode`,
> which makes the fan enter "dust cleaning mode," causing it to ramp up to
> max speed
> and then back down to 0 RPM about 10 times.)
> 
> Attachments:
> - DSDT in `DSDT.gz`
> - `dmidecode` in `dmidecode.txt`
> 
> Data Collected during `stress -c $(nproc)` until thermal throttling:
> - EC information collected in a CSV file named `ec.csv`
>   (using `sudo ec_probe monitor -i 0.5 -r ec.csv` from the NBFC project)
> - `sensors` information in `sensors.log`
> - CPU frequencies in `cpu-freq.log`
> - `dmesg` in `dmesg-live.log`
> 
> Thank you for your time.
> 
> Best regards,
> Sourajyoti Basak


Hello everyone,

Just a gentle ping on this bug report. The thermal throttling issue is
still present. Please let me know if there is any further ACPI/EC
debugging information I can provide.

Best Regards,
Sourajyoti Basak