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authorSrinivas Pandruvada <srinivas.pandruvada@linux.intel.com>2023-04-21 01:05:14 +0300
committerHans de Goede <hdegoede@redhat.com>2023-05-09 12:54:42 +0300
commit8a54e2253e4c25e5b61c9a9bee157bb52da5d432 (patch)
tree7f9665171b90e9e775d6aecb41c987393f6d5f6d /Documentation/admin-guide/pm
parent334e3516f23360e0690511fb43052959111f51b4 (diff)
downloadlinux-8a54e2253e4c25e5b61c9a9bee157bb52da5d432.tar.xz
platform/x86/intel-uncore-freq: Uncore frequency control via TPMI
Implement support of uncore frequency control via TPMI (Topology Aware Register and PM Capsule Interface). This driver provides the similar functionality as the current uncore frequency driver using MSRs. The hardware interface to read/write is basically substitution of MSR 0x620 and 0x621. There are specific MMIO offset and bits to get/set minimum and maximum uncore ratio, similar to MSRs. The scope of the uncore MSRs is package/die. But new generation of CPUs have more granular control at a cluster level. Each package/die can have multiple power domains, which further can have multiple clusters. The TPMI interface allows control at cluster level. The primary use case for uncore sysfs is to set maximum and minimum uncore frequency to reduce power consumption or latency. The current uncore sysfs control is per package/die. This is enough for the majority of users as workload will move to different power domains as it moves between different CPUs. The current uncore sysfs provides controls at package/die level. When user sets maximum/minimum limits, the driver sets the same limits to each cluster. Here number of power domains = number of resources in this aux device. There are offsets and bits to discover number of clusters and offset for each cluster level controls. The TPMI documentation can be downloaded from: https://github.com/intel/tpmi_power_management Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Reviewed-by: Zhang Rui <rui.zhang@intel.com> Tested-by: Wendy Wang <wendy.wang@intel.com> Link: https://lore.kernel.org/r/20230420220514.747573-1-srinivas.pandruvada@linux.intel.com Reviewed-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
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