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diff --git a/Documentation/hwmon/dell-smm-hwmon.rst b/Documentation/hwmon/dell-smm-hwmon.rst index 3bf77a5df995..977263cb57a8 100644 --- a/Documentation/hwmon/dell-smm-hwmon.rst +++ b/Documentation/hwmon/dell-smm-hwmon.rst @@ -34,6 +34,9 @@ Name Perm Description =============================== ======= ======================================= fan[1-3]_input RO Fan speed in RPM. fan[1-3]_label RO Fan label. +fan[1-3]_min RO Minimal Fan speed in RPM +fan[1-3]_max RO Maximal Fan speed in RPM +fan[1-3]_target RO Expected Fan speed in RPM pwm[1-3] RW Control the fan PWM duty-cycle. pwm1_enable WO Enable or disable automatic BIOS fan control (not supported on all laptops, @@ -43,6 +46,9 @@ temp[1-10]_input RO Temperature reading in milli-degrees temp[1-10]_label RO Temperature sensor label. =============================== ======= ======================================= +Due to the nature of the SMM interface, each pwmX attribute controls +fan number X. + Disabling automatic BIOS fan control ------------------------------------ @@ -83,6 +89,13 @@ probe the BIOS on your machine and discover the appropriate codes. Again, when you find new codes, we'd be happy to have your patches! +``thermal`` interface +--------------------------- + +The driver also exports the fans as thermal cooling devices with +``type`` set to ``dell-smm-fan[1-3]``. This allows for easy fan control +using one of the thermal governors. + Module parameters ----------------- @@ -162,3 +175,217 @@ obtain the same information and to control the fan status. The ioctl interface can be accessed from C programs or from shell using the i8kctl utility. See the source file of ``i8kutils`` for more information on how to use the ioctl interface. + +SMM Interface +------------- + +.. warning:: The SMM interface was reverse-engineered by trial-and-error + since Dell did not provide any Documentation, + please keep that in mind. + +The driver uses the SMM interface to send commands to the system BIOS. +This interface is normally used by Dell's 32-bit diagnostic program or +on newer notebook models by the buildin BIOS diagnostics. +The SMM may cause short hangs when the BIOS code is taking too long to +execute. + +The SMM handler inside the system BIOS looks at the contents of the +``eax``, ``ebx``, ``ecx``, ``edx``, ``esi`` and ``edi`` registers. +Each register has a special purpose: + +=============== ================================== +Register Purpose +=============== ================================== +eax Holds the command code before SMM, + holds the first result after SMM. +ebx Holds the arguments. +ecx Unknown, set to 0. +edx Holds the second result after SMM. +esi Unknown, set to 0. +edi Unknown, set to 0. +=============== ================================== + +The SMM handler can signal a failure by either: + +- setting the lower sixteen bits of ``eax`` to ``0xffff`` +- not modifying ``eax`` at all +- setting the carry flag (legacy SMM interface only) + +Legacy SMM Interface +-------------------- + +When using the legacy SMM interface, a SMM is triggered by writing the least significant byte +of the command code to the special ioports ``0xb2`` and ``0x84``. This interface is not +described inside the ACPI tables and can thus only be detected by issuing a test SMM call. + +WMI SMM Interface +----------------- + +On modern Dell machines, the SMM calls are done over ACPI WMI: + +:: + + #pragma namespace("\\\\.\\root\\dcim\\sysman\\diagnostics") + [WMI, Provider("Provider_DiagnosticsServices"), Dynamic, Locale("MS\\0x409"), + Description("RunDellDiag"), guid("{F1DDEE52-063C-4784-A11E-8A06684B9B01}")] + class LegacyDiags { + [key, read] string InstanceName; + [read] boolean Active; + + [WmiMethodId(1), Implemented, read, write, Description("Legacy Method ")] + void Execute([in, out] uint32 EaxLen, [in, out, WmiSizeIs("EaxLen") : ToInstance] uint8 EaxVal[], + [in, out] uint32 EbxLen, [in, out, WmiSizeIs("EbxLen") : ToInstance] uint8 EbxVal[], + [in, out] uint32 EcxLen, [in, out, WmiSizeIs("EcxLen") : ToInstance] uint8 EcxVal[], + [in, out] uint32 EdxLen, [in, out, WmiSizeIs("EdxLen") : ToInstance] uint8 EdxVal[]); + }; + +Some machines support only the WMI SMM interface, while some machines support both interfaces. +The driver automatically detects which interfaces are present and will use the WMI SMM interface +if the legacy SMM interface is not present. The WMI SMM interface is usually slower than the +legacy SMM interface since ACPI methods need to be called in order to trigger a SMM. + +SMM command codes +----------------- + +=============== ======================= ================================================ +Command Code Command Name Description +=============== ======================= ================================================ +``0x0025`` Get Fn key status Returns the Fn key pressed after SMM: + + - 9th bit in ``eax`` indicates Volume up + - 10th bit in ``eax`` indicates Volume down + - both bits indicate Volume mute + +``0xa069`` Get power status Returns current power status after SMM: + + - 1st bit in ``eax`` indicates Battery connected + - 3th bit in ``eax`` indicates AC connected + +``0x00a3`` Get fan state Returns current fan state after SMM: + + - 1st byte in ``eax`` holds the current + fan state (0 - 2 or 3) + +``0x01a3`` Set fan state Sets the fan speed: + + - 1st byte in ``ebx`` holds the fan number + - 2nd byte in ``ebx`` holds the desired + fan state (0 - 2 or 3) + +``0x02a3`` Get fan speed Returns the current fan speed in RPM: + + - 1st byte in ``ebx`` holds the fan number + - 1st word in ``eax`` holds the current + fan speed in RPM (after SMM) + +``0x03a3`` Get fan type Returns the fan type: + + - 1st byte in ``ebx`` holds the fan number + - 1st byte in ``eax`` holds the + fan type (after SMM): + + - 5th bit indicates docking fan + - 1 indicates Processor fan + - 2 indicates Motherboard fan + - 3 indicates Video fan + - 4 indicates Power supply fan + - 5 indicates Chipset fan + - 6 indicates other fan type + +``0x04a3`` Get nominal fan speed Returns the nominal RPM in each fan state: + + - 1st byte in ``ebx`` holds the fan number + - 2nd byte in ``ebx`` holds the fan state + in question (0 - 2 or 3) + - 1st word in ``eax`` holds the nominal + fan speed in RPM (after SMM) + +``0x05a3`` Get fan speed tolerance Returns the speed tolerance for each fan state: + + - 1st byte in ``ebx`` holds the fan number + - 2nd byte in ``ebx`` holds the fan state + in question (0 - 2 or 3) + - 1st byte in ``eax`` returns the speed + tolerance + +``0x10a3`` Get sensor temperature Returns the measured temperature: + + - 1st byte in ``ebx`` holds the sensor number + - 1st byte in ``eax`` holds the measured + temperature (after SMM) + +``0x11a3`` Get sensor type Returns the sensor type: + + - 1st byte in ``ebx`` holds the sensor number + - 1st byte in ``eax`` holds the + temperature type (after SMM): + + - 1 indicates CPU sensor + - 2 indicates GPU sensor + - 3 indicates SODIMM sensor + - 4 indicates other sensor type + - 5 indicates Ambient sensor + - 6 indicates other sensor type + +``0xfea3`` Get SMM signature Returns Dell signature if interface + is supported (after SMM): + + - ``eax`` holds 1145651527 + (0x44494147 or "DIAG") + - ``edx`` holds 1145392204 + (0x44454c4c or "DELL") + +``0xffa3`` Get SMM signature Same as ``0xfea3``, check both. +=============== ======================= ================================================ + +There are additional commands for enabling (``0x31a3`` or ``0x35a3``) and +disabling (``0x30a3`` or ``0x34a3``) automatic fan speed control. +The commands are however causing severe sideeffects on many machines, so +they are not used by default. + +On several machines (Inspiron 3505, Precision 490, Vostro 1720, ...), the +fans supports a 4th "magic" state, which signals the BIOS that automatic +fan control should be enabled for a specific fan. +However there are also some machines who do support a 4th regular fan state too, +but in case of the "magic" state, the nominal RPM reported for this state is a +placeholder value, which however is not always detectable. + +Firmware Bugs +------------- + +The SMM calls can behave erratic on some machines: + +======================================================= ================= +Firmware Bug Affected Machines +======================================================= ================= +Reading of fan states return spurious errors. Precision 490 + +Reading of fan types causes erratic fan behaviour. Studio XPS 8000 + + Studio XPS 8100 + + Inspiron 580 + + Inspiron 3505 + +Fan-related SMM calls take too long (about 500ms). Inspiron 7720 + + Vostro 3360 + + XPS 13 9333 + + XPS 15 L502X +======================================================= ================= + +In case you experience similar issues on your Dell machine, please +submit a bugreport on bugzilla to we can apply workarounds. + +Limitations +----------- + +The SMM calls can take too long to execute on some machines, causing +short hangs and/or audio glitches. +Also the fan state needs to be restored after suspend, as well as +the automatic mode settings. +When reading a temperature sensor, values above 127 degrees indicate +a BIOS read error or a deactivated sensor. |