cpuidle: pseries: Add function to parse extended CEDE records
Currently we use CEDE with latency-hint 0 as the only other idle state on a dedicated LPAR apart from the polling "snooze" state. The platform might support additional extended CEDE idle states, which can be discovered through the "ibm,get-system-parameter" rtas-call made with CEDE_LATENCY_TOKEN. This patch adds a function to obtain information about the extended CEDE idle states from the platform and parse the contents to populate an array of extended CEDE states. These idle states thus discovered will be added to the cpuidle framework in the next patch. dmesg on a POWER8 and POWER9 LPAR, demonstrating the output of parsing the extended CEDE latency parameters are as follows POWER8 [ 10.093279] xcede : xcede_record_size = 10 [ 10.093285] xcede : Record 0 : hint = 1, latency = 0x3c00 tb ticks, Wake-on-irq = 1 [ 10.093291] xcede : Record 1 : hint = 2, latency = 0x4e2000 tb ticks, Wake-on-irq = 0 [ 10.093297] cpuidle : Skipping the 2 Extended CEDE idle states POWER9 [ 5.913180] xcede : xcede_record_size = 10 [ 5.913183] xcede : Record 0 : hint = 1, latency = 0x400 tb ticks, Wake-on-irq = 1 [ 5.913188] xcede : Record 1 : hint = 2, latency = 0x3e8000 tb ticks, Wake-on-irq = 0 [ 5.913193] cpuidle : Skipping the 2 Extended CEDE idle states Signed-off-by:Gautham R. Shenoy <ego@linux.vnet.ibm.com> [mpe: Make space for 16 records, drop memset, minor cleanup & formatting] Signed-off-by:
Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/1596087177-30329-3-git-send-email-ego@linux.vnet.ibm.com
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