| .. SPDX-License-Identifier: GPL-2.0-only |
| |
| =============================================================================================== |
| Kernel driver yogafan |
| =============================================================================================== |
| |
| Supported chips: |
| |
| * Lenovo Yoga, Legion, IdeaPad, Slim, Flex, and LOQ Embedded Controllers |
| * Prefix: 'yogafan' |
| * Addresses: ACPI handle (See Database Below) |
| |
| Author: Sergio Melas <sergiomelas@gmail.com> |
| |
| Description |
| ----------- |
| |
| This driver provides fan speed monitoring for modern Lenovo consumer laptops. |
| Most Lenovo laptops do not provide fan tachometer data through standard |
| ISA/LPC hardware monitoring chips. Instead, the data is stored in the |
| Embedded Controller (EC) and exposed via ACPI. |
| |
| The driver implements a **Rate-Limited Lag (RLLag)** filter to handle |
| the low-resolution and jittery sampling found in Lenovo EC firmware. |
| |
| Hardware Identification and Multiplier Logic |
| -------------------------------------------- |
| |
| The driver supports two distinct EC architectures. Differentiation is handled |
| deterministically via a DMI Product Family quirk table during the probe phase, |
| eliminating the need for runtime heuristics. |
| |
| 1. 8-bit EC Architecture (Multiplier: 100) |
| |
| - **Families:** Yoga, IdeaPad, Slim, Flex. |
| - **Technical Detail:** These models allocate a single 8-bit register for |
| tachometer data. Since 8-bit fields are limited to a value of 255, the |
| BIOS stores fan speed in units of 100 RPM (e.g., 42 = 4200 RPM). |
| |
| 2. 16-bit EC Architecture (Multiplier: 1) |
| |
| - **Families:** Legion, LOQ. |
| - **Technical Detail:** High-performance gaming models require greater |
| precision for fans exceeding 6000 RPM. These use a 16-bit word (2 bytes) |
| storing the raw RPM value directly. |
| |
| Filter Details |
| -------------- |
| |
| The RLLag filter is a passive discrete-time first-order lag model that ensures: |
| - **Smoothing:** Low-resolution step increments are smoothed into 1-RPM increments. |
| - **Slew-Rate Limiting:** Prevents unrealistic readings by capping the change |
| to 1500 RPM/s, matching physical fan inertia. |
| - **Polling Independence:** The filter math scales based on the time delta |
| between userspace reads, ensuring a consistent physical curve regardless |
| of polling frequency. |
| |
| Suspend and Resume |
| ------------------ |
| |
| The driver utilizes the boottime clock (ktime_get_boottime()) to calculate the |
| sampling delta. This ensures that time spent in system suspend is accounted |
| for. If the delta exceeds 5 seconds (e.g., after waking the laptop), the |
| filter automatically resets to the current hardware value to prevent |
| reporting "ghost" RPM data from before the sleep state. |
| |
| Usage |
| ----- |
| |
| The driver exposes standard hwmon sysfs attributes: |
| |
| =============== ============================ |
| Attribute Description |
| fanX_input Filtered fan speed in RPM. |
| =============== ============================ |
| |
| |
| Note: If the hardware reports 0 RPM, the filter is bypassed and 0 is reported |
| immediately to ensure the user knows the fan has stopped. |
| |
| |
| ==================================================================================================== |
| LENOVO FAN CONTROLLER: MASTER REFERENCE DATABASE (2026) |
| ==================================================================================================== |
| |
| :: |
| |
| MODEL (DMI PN) | FAMILY / SERIES | EC OFFSET | FULL ACPI OBJECT PATH | WIDTH | MULTiplier |
| ---------------------------------------------------------------------------------------------------- |
| 82N7 | Yoga 14cACN | 0x06 | \_SB.PCI0.LPC0.EC0.FANS | 8-bit | 100 |
| 80V2 / 81C3 | Yoga 710/720 | 0x06 | \_SB.PCI0.LPC0.EC0.FAN0 | 8-bit | 100 |
| 83E2 / 83DN | Yoga Pro 7/9 | 0xFE | \_SB.PCI0.LPC0.EC0.FANS | 8-bit | 100 |
| 82A2 / 82A3 | Yoga Slim 7 | 0x06 | \_SB.PCI0.LPC0.EC0.FANS | 8-bit | 100 |
| 81YM / 82FG | IdeaPad 5 | 0x06 | \_SB.PCI0.LPC0.EC0.FAN0 | 8-bit | 100 |
| 82JW / 82JU | Legion 5 (AMD) | 0xFE/0xFF | \_SB.PCI0.LPC0.EC0.FANS (Fan1) | 16-bit | 1 |
| 82JW / 82JU | Legion 5 (AMD) | 0xFE/0xFF | \_SB.PCI0.LPC0.EC0.FA2S (Fan2) | 16-bit | 1 |
| 82WQ | Legion 7i (Int) | 0xFE/0xFF | \_SB.PCI0.LPC0.EC0.FANS (Fan1) | 16-bit | 1 |
| 82WQ | Legion 7i (Int) | 0xFE/0xFF | \_SB.PCI0.LPC0.EC0.FA2S (Fan2) | 16-bit | 1 |
| 82XV / 83DV | LOQ 15/16 | 0xFE/0xFF | \_SB.PCI0.LPC0.EC0.FANS /FA2S | 16-bit | 1 |
| 83AK | ThinkBook G6 | 0x06 | \_SB.PCI0.LPC0.EC0.FAN0 | 8-bit | 100 |
| 81X1 | Flex 5 | 0x06 | \_SB.PCI0.LPC0.EC0.FAN0 | 8-bit | 100 |
| *Legacy* | Pre-2020 Models | 0x06 | \_SB.PCI0.LPC.EC.FAN0 | 8-bit | 100 |
| ---------------------------------------------------------------------------------------------------- |
| |
| METHODOLOGY & IDENTIFICATION: |
| |
| 1. DSDT ANALYSIS (THE PATH): |
| BIOS ACPI tables were analyzed using 'iasl' and cross-referenced with |
| public dumps. Internal labels (FANS, FAN0, FA2S) are mapped to |
| EmbeddedControl OperationRegion offsets. |
| |
| 2. EC MEMORY MAPPING (THE OFFSET): |
| Validated by matching NBFC (NoteBook FanControl) XML logic with DSDT Field |
| definitions found in BIOS firmware. |
| |
| 3. DATA-WIDTH ANALYSIS (THE MULTIPLIER): |
| - 8-bit (Multiplier 100): Standard for Yoga/IdeaPad. Raw values (0-255). |
| - 16-bit (Multiplier 1): Standard for Legion/LOQ. Two registers (0xFE/0xFF). |
| |
| |
| References |
| ---------- |
| |
| 1. **ACPI Specification (Field Objects):** Documentation on how 8-bit vs 16-bit |
| fields are accessed in OperationRegions. |
| https://uefi.org/specs/ACPI/6.5/05_ACPI_Software_Programming_Model.html#field-objects |
| |
| 2. **NBFC Projects:** Community-driven reverse engineering |
| of Lenovo Legion/LOQ EC memory maps (16-bit raw registers). |
| https://github.com/hirschmann/nbfc/tree/master/Configs |
| |
| 3. **Linux Kernel Timekeeping API:** Documentation for ktime_get_boottime() and |
| handling deltas across suspend states. |
| https://www.kernel.org/doc/html/latest/core-api/timekeeping.html |
| |
| 4. **Lenovo IdeaPad Laptop Driver:** Reference for DMI-based hardware |
| feature gating in Lenovo laptops. |
| https://github.com/torvalds/linux/blob/master/drivers/platform/x86/ideapad-laptop.c |
