Embedded Controller Firmware

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Revision as of 23:01, 4 October 2006 by Hmh (Talk | contribs) (Old-style ThinkPad EC firmware: add tpctl, tpb)
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ThinkPad Embedded Controller Firmware

The ThinkPad has an embedded microcontroller (EC) which is responsible for many of the background tasks on a laptop. Embedded Controller Chips lists the different embedded microcontrollers found on various ThinkPads. This page concerns itself with the various embedded controller firmwares.

As a rule, if you are not using the latest available firmware for your ThinkPad, you are likely to be the unlucky chap that will find out some new code hits a firmware bug that was fixed by IBM or Lenovo. Do yourself a favour and always keep your ThinkPad's firmware up-to-date.

Old-style ThinkPad EC firmware

Not much is known about the ECs on the older numeric-series ThinkPads, or the early A, X and T-series models. These microcontrollers don't seem to support field-upgradeable firmware, and only the BIOS SMAPI and DSDT ACPI interfaces are really available for driver writers.

  • Interfaces:
    • EC register map
    • SMAPI
    • CMOS memory map

New-style ThinkPad EC firmware

Apparently, all newer ThinkPad ECs are a Renesas H8S/2161BV or another compatible H8S/300 microcontroller with very similar firmware.

  • Interfaces:
    • Forward-compatible EC register map
    • LPC3A (?), LPC3B (HDAPS firmware, Battery information)
    • SMAPI
    • CMOS memory map
tpctl and other drivers, please someone expand on how well they work with the new ThinkPads

Firmware issues

Various bugs have been observed in the ThinkPad EC firmware of various models. Most of them were fixed in later revisions, but a few are either very dangerous and driver writers need to always work around them, or have never been fixed. One must keep in mind that many of the bugs fixed by IBM or Lenovo could cause serious problems, but might never be noticed by driver developers, because they usually keep their ThinkPads up-to-date. People that don't keep their ThinkPad firmware up-to-date are excellent guinea pigs...

Bug: Advanced battery query causes EC hang

  • Models affected:
    • T40, T40p, T41, T41p, T42, T42p: all models affected, no fix available
    • T43 26xx, T43p: fixed on firmware 1YHT28WW (1.05) and newer
    • T43 18xx, R52: likely buggy, unknown status (might be fixed in latest firmwares)
    • other ThinkPads featuring advanced battery queries: unknown status; every model supported by tp_smapi advanced battery information is a candidate for this bug

The EC LPC3B advanced battery query function 0x0B (only used by tp_smapi) has a hideous bug that causes the EC to misbehave and crash (usually hanging the entire ThinkPad). This function must never be called on a buggy firmware.

Bug: Fan control loop status is not initialized

  • Models affected:
    • T43, T43p, R52
    • no information about other models, please report on linux-thinkpad ML, see link above

The EC does not correctly initializes its 0x2f (fan control) register, so ibm-acpi cannot determine the correct status of the fan control until something writes to the fan control register for the first time.

Bug: Fan control loop pulses the fan in an annoying pattern

  • Models affected:
    • T40, T40p, T41, T41p, T42, T42p: fixed by firmware 1RHT70WW (3.03) and later
    • T43, T43p, R52: IBM provided a broken firmware fix, so they are all affected
    • other newer models: unknown status

The fan control loop will vary the fan speed quite a lot, in a very annoying pattern. The broken fix on the T43 firmware causes annoying pulses every 30s.

Bug: Tachometer registers not invalidated in disengaged mode

  • Severity: low
  • Fix: none available
  • Models affected:
    • Nearly all ThinkPad models

When the fan control loop is placed in disengaged mode (bit 6 of EC register 0x2f is set) where no tachometer readings take place, the EC does not set the tachometer registers (0x84, 0x85) to 0xFF to signal an invalid reading. Instead, the registers are simply not updated anymore and retain the last tachometer reading that took place.

See also