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It is useful to obtain the results of MSR queries as well as to update MSR registers, so add a command these tasks. Signed-off-by: Simon Glass <sjg@chromium.org>
61 lines
1.1 KiB
ReStructuredText
61 lines
1.1 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+
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.. index::
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single: msr (command)
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msr command
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===========
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Synopsis
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--------
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::
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msr read <op>
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msr write <op> <hi> <lo>
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Description
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-----------
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The msr command reads and writes machine-status registers (MSRs) on x86 CPUs.
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The information is a 64-bit value split into two parts, <hi> for the top 32
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bits and <lo> for the bottom 32 bits.
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The operation <op> selects what information is read or written.
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msr read
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~~~~~~~~
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This reads an MSR and displays the value obtained.
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msr write
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~~~~~~~~~
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This writes a value to an MSR.
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Configuration
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-------------
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The msr command is only available on x86.
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Return value
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------------
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The return value $? is 0 (true).
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Example
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-------
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This shows reading msr 0x194 which is MSR_FLEX_RATIO on Intel CPUs::
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=> msr read 194
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00000000 00011200 # Bits 16 (flex ratio enable) and 20 (lock) are set
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This shows adjusting the energy-performance bias on an Intel CPU::
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=> msr read 1b0
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00000000 00000006 # 6 means 'normal'
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=> msr write 1b0 0 f # change to power-save
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=> msr read 1b0
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00000000 0000000f
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