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authorPierre Gondois2022-05-18 11:08:59 +0200
committerRafael J. Wysocki2022-05-19 19:45:34 +0200
commit6380b7b2b29da9d9c5ab2d4a265901cd93ba3696 (patch)
tree67d27acc66c5834953f21bac66c4e5d2b471d63f /include/acpi
parent72f2ecb7ece7c1d89758d4929d98e95d95fe7199 (diff)
ACPI: CPPC: Assume no transition latency if no PCCT
The transition_delay_us (struct cpufreq_policy) is currently defined as: Preferred average time interval between consecutive invocations of the driver to set the frequency for this policy. To be set by the scaling driver (0, which is the default, means no preference). The transition_latency represents the amount of time necessary for a CPU to change its frequency. A PCCT table advertises mutliple values: - pcc_nominal: Expected latency to process a command, in microseconds - pcc_mpar: The maximum number of periodic requests that the subspace channel can support, reported in commands per minute. 0 indicates no limitation. - pcc_mrtt: The minimum amount of time that OSPM must wait after the completion of a command before issuing the next command, in microseconds. cppc_get_transition_latency() allows to get the max of them. commit d4f3388afd48 ("cpufreq / CPPC: Set platform specific transition_delay_us") allows to select transition_delay_us based on the platform, and fallbacks to cppc_get_transition_latency() otherwise. If _CPC objects are not using PCC channels (no PPCT table), the transition_delay_us is set to CPUFREQ_ETERNAL, leading to really long periods between frequency updates (~4s). If the desired_reg, where performance requests are written, is in SystemMemory or SystemIo ACPI address space, there is no delay in requests. So return 0 instead of CPUFREQ_ETERNAL, leading to transition_delay_us being set to LATENCY_MULTIPLIER us (1000 us). This patch also adds two macros to check the address spaces. Signed-off-by: Pierre Gondois <pierre.gondois@arm.com> Reviewed-by: Sudeep Holla <sudeep.holla@arm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'include/acpi')
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