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a6e232f786
This patch adds the description to explain the TDP reporting mechanism and accumulated power algorithm. Signed-off-by: Huang Rui <ray.huang@amd.com> Cc: Borislav Petkov <bp@alien8.de> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
103 lines
3.5 KiB
Plaintext
103 lines
3.5 KiB
Plaintext
Kernel driver fam15h_power
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==========================
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Supported chips:
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* AMD Family 15h Processors
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* AMD Family 16h Processors
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Prefix: 'fam15h_power'
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Addresses scanned: PCI space
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Datasheets:
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BIOS and Kernel Developer's Guide (BKDG) For AMD Family 15h Processors
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BIOS and Kernel Developer's Guide (BKDG) For AMD Family 16h Processors
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AMD64 Architecture Programmer's Manual Volume 2: System Programming
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Author: Andreas Herrmann <herrmann.der.user@googlemail.com>
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Description
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-----------
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1) Processor TDP (Thermal design power)
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Given a fixed frequency and voltage, the power consumption of a
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processor varies based on the workload being executed. Derated power
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is the power consumed when running a specific application. Thermal
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design power (TDP) is an example of derated power.
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This driver permits reading of registers providing power information
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of AMD Family 15h and 16h processors via TDP algorithm.
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For AMD Family 15h and 16h processors the following power values can
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be calculated using different processor northbridge function
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registers:
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* BasePwrWatts: Specifies in watts the maximum amount of power
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consumed by the processor for NB and logic external to the core.
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* ProcessorPwrWatts: Specifies in watts the maximum amount of power
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the processor can support.
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* CurrPwrWatts: Specifies in watts the current amount of power being
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consumed by the processor.
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This driver provides ProcessorPwrWatts and CurrPwrWatts:
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* power1_crit (ProcessorPwrWatts)
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* power1_input (CurrPwrWatts)
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On multi-node processors the calculated value is for the entire
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package and not for a single node. Thus the driver creates sysfs
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attributes only for internal node0 of a multi-node processor.
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2) Accumulated Power Mechanism
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This driver also introduces an algorithm that should be used to
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calculate the average power consumed by a processor during a
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measurement interval Tm. The feature of accumulated power mechanism is
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indicated by CPUID Fn8000_0007_EDX[12].
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* Tsample: compute unit power accumulator sample period
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* Tref: the PTSC counter period
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* PTSC: performance timestamp counter
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* N: the ratio of compute unit power accumulator sample period to the
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PTSC period
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* Jmax: max compute unit accumulated power which is indicated by
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MaxCpuSwPwrAcc MSR C001007b
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* Jx/Jy: compute unit accumulated power which is indicated by
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CpuSwPwrAcc MSR C001007a
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* Tx/Ty: the value of performance timestamp counter which is indicated
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by CU_PTSC MSR C0010280
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* PwrCPUave: CPU average power
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i. Determine the ratio of Tsample to Tref by executing CPUID Fn8000_0007.
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N = value of CPUID Fn8000_0007_ECX[CpuPwrSampleTimeRatio[15:0]].
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ii. Read the full range of the cumulative energy value from the new
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MSR MaxCpuSwPwrAcc.
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Jmax = value returned.
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iii. At time x, SW reads CpuSwPwrAcc MSR and samples the PTSC.
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Jx = value read from CpuSwPwrAcc and Tx = value read from
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PTSC.
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iv. At time y, SW reads CpuSwPwrAcc MSR and samples the PTSC.
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Jy = value read from CpuSwPwrAcc and Ty = value read from
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PTSC.
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v. Calculate the average power consumption for a compute unit over
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time period (y-x). Unit of result is uWatt.
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if (Jy < Jx) // Rollover has occurred
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Jdelta = (Jy + Jmax) - Jx
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else
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Jdelta = Jy - Jx
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PwrCPUave = N * Jdelta * 1000 / (Ty - Tx)
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This driver provides PwrCPUave and interval(default is 10 millisecond
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and maximum is 1 second):
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* power1_average (PwrCPUave)
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* power1_average_interval (Interval)
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The power1_average_interval can be updated at /etc/sensors3.conf file
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as below:
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chip "fam15h_power-*"
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set power1_average_interval 0.01
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Then save it with "sensors -s".
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