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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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Linux uses CPUID.MWAIT.EDX to validate the C-states reported by ACPI, silently discarding states which are not supported by the HW. This test is too restrictive, as some HW now uses sparse sub-state numbering, so the sub-state number may be higher than the number of sub-states... Also, rather than silently ignoring an invalid state, we should complain about a firmware bug. In practice... Bay Trail systems originally supported C6-no-shrink as MWAIT sub-state 0x58, and in CPUID.MWAIT.EDX 0x03000000 indicated that there were 3 MWAIT-C6 sub-states. So acpi_idle would discard that C-state because 8 >= 3. Upon discovering this issue, the ucode was updated so that C6-no-shrink was also exported as 0x51, and the BIOS was updated to match. However, systems shipped with 0x58, will never get a BIOS update, and this patch allows Linux to see C6-no-shrink on early Bay Trail. Signed-off-by: Len Brown <len.brown@intel.com> |
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| .. | ||
| boot.c | ||
| cstate.c | ||
| Makefile | ||
| sleep.c | ||
| sleep.h | ||
| wakeup_32.S | ||
| wakeup_64.S | ||