This page captures the investigation notes and references to implementation for ACPI device runtime power management.
Device power management on NXP I.MX8MP Platform
We have implemented device power management for few devices (I2C, UART) in IMX8MP platform. Changes to different components are given below.
EDK2
https://gitlab.com/LinaroLtd/clientpc/edk2-platforms/-/merge_requests/4
Implements SCMI protocol support
SCMI AML methods to set clock state and get clock rate
Device power management for I2C and UART
GCLK AML method to get clock rate using SCMI
TF-A
https://gitlab.com/LinaroLtd/clientpc/tf-a/-/merge_requests/2/
Add support for SCMI protocol
Implements a simple clock driver for I.MX8MP platform and SCMI clock management support
The implementation includes an SCMI server implemented in TF-A and a SCMI agent implemented in AML.
AML Code
Device (I2C1)
{
Name (_HID, "NXP0104")
Name (_HRV, 0x1)
Name (_UID, 0x1)
Name (_CLK, 13)
Method (_STA)
{
Return(0xf)
}
Name (_PRS, ResourceTemplate () // _PRS: Possible Resource Settings
{
Interrupt(ResourceConsumer, Level, ActiveHigh, Exclusive) { 67 }
})
Method (_CRS, 0x0, NotSerialized)
{
Name ( RBUF, ResourceTemplate () {
MEMORY32FIXED(ReadWrite, 0x30A20000, 0x14, )
Interrupt(ResourceConsumer, Level, ActiveHigh, Exclusive) { 67 }
})
Return(RBUF)
}
Method (_PS0, 0, NotSerialized) // _PS0: Power State 0
{
SC07(_CLK, 1)
}
Method (_PS3, 0, NotSerialized) // _PS3: Power State 3
{
SC07(_CLK, 0)
}
}
// Operation Region for Shared memory transport
OperationRegion(SHM, SystemMemory, 0x403f0000, 44)
Field(SHM, ByteAcc, NoLock, Preserve) {
RES1, 32,
SCHS, 32,
RES2, 64,
SCHF, 32,
SLEN, 32,
SMSH, 32,
SPLD, 128,
}
// SC07 - SCMI CLOCK_CONFIG_SET
// Arg0: SCMI Clock ID
// Arg1: Clock Attributes ( 1 -> Enable, 0 -> Disable)
// Returns: 1 if config is set succesfully, 0 otherwise
Method (SC07, 2, Serialized)
{
Name(BUFF, Buffer(8){})
CreateDWordField(BUFF, 0, PLW0)
CreateDWordField(BUFF, 4, PLW1)
PLW0 = Arg0
PLW1 = Arg1
local0 = SMT(0x14, 0x7, BUFF)
CreateDWordField(local0, 0, RET)
Return (RET)
}
// SMT - Interface to send SCMI message over shared memory channel
// Arg0: SCMI Protocol ID
// Arg1: SCMI Message ID
// Arg2: SCMI Input Argument Buffer
// Returns: SCMI Payload
Method (SMT, 3, Serialized)
{
// SCMI Message header with SCMI protocol and message ID
Name(MSGH, Buffer(8){})
CreateField(MSGH, 10, 8, PROI)
CreateField(MSGH, 0, 8, MSGI)
PROI = Arg0
MSGI = Arg1
SCHS = 0x0
SCHF = 0x0
SMSH = MSGH
SLEN = 4 + sizeof(Arg2)
SPLD = Arg2
// SMC call
OperationRegion(AFFH, FFixedHW, 1, 8)
Field (AFFH, BufferAcc, NoLock, Preserve) { SMCC, 64 }
Name(BUFF, Buffer(8){})
CreateQWordField(BUFF, 0x00, BFX0)
BFX0 = 0xC20000FE // SCMI FID
BUFF = (SMCC = BUFF)
Return (SPLD)
}