ACPI: allow C3 > 1000usec (a6d72c18) · Commits · 戴 / test

Do for C3 what the previous patch did for C2. The C2 patch was in response to a highly visible and multiply reported C-state/turbo failure, while this change has no bug report in-hand. This will enable C3 in Linux on systems where BIOS overstates C3 latency in _CST. It will also enable future systems which may actually have C3 > 1000usec. Linux has always ignored ACPI BIOS C3 with exit latency > 1000 usec, and the ACPI spec is clear that is correct FADT-supplied C3. However, the ACPI spec explicitly states that _CST-supplied C-states have no latency limits. So move the 1000usec C3 test out of the code shared by FADT and _CST code-paths, and into the FADT-specific path. Signed-off-by:

Len Brown <len.brown@intel.com>

drivers/acpi/processor_idle.c

+11 −10

Original line number	Diff line number	Diff line
		@@ -316,6 +316,17 @@ static int acpi_processor_get_power_info_fadt(struct acpi_processor *pr)
		pr->power.states[ACPI_STATE_C2].address = 0;
		}

		/*
		* FADT supplied C3 latency must be less than or equal to
		* 1000 microseconds.
		*/
		if (acpi_gbl_FADT.C3latency > ACPI_PROCESSOR_MAX_C3_LATENCY) {
		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
		"C3 latency too large [%d]\n", acpi_gbl_FADT.C3latency));
		/* invalidate C3 */
		pr->power.states[ACPI_STATE_C3].address = 0;
		}

		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
		"lvl2[0x%08x] lvl3[0x%08x]\n",
		pr->power.states[ACPI_STATE_C2].address,
		@@ -532,16 +543,6 @@ static void acpi_processor_power_verify_c3(struct acpi_processor *pr,
		if (!cx->address)
		return;

		/*
		* C3 latency must be less than or equal to 1000
		* microseconds.
		*/
		else if (cx->latency > ACPI_PROCESSOR_MAX_C3_LATENCY) {
		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
		"latency too large [%d]\n", cx->latency));
		return;
		}

		/*
		* PIIX4 Erratum #18: We don't support C3 when Type-F (fast)
		* DMA transfers are used by any ISA device to avoid livelock.

Admin message