diff mbox series

[v1,2/5] ACPI: bus: Set CPPC _OSC bits for all and when CPPC_LIB is supported

Message ID 20220511134559.1466925-2-pierre.gondois@arm.com (mailing list archive)
State Changes Requested, archived
Headers show
Series [v1,1/5] ACPI: CPPC: Check _OSC for flexible address space | expand

Commit Message

Pierre Gondois May 11, 2022, 1:45 p.m. UTC
The _OSC method allows the OS and firmware to communicate about
supported features/capabitlities. It also allows the OS to take
control of some features.

In ACPI 6.4, s6.2.11.2 Platform-Wide OSPM Capabilities, the CPPC
(resp. v2) bit should be set by the OS if it 'supports controlling
processor performance via the interfaces described in the _CPC
object'.

The OS supports CPPC and parses the _CPC object only if
CONFIG_ACPI_CPPC_LIB is set. Replace the x86 specific
boot_cpu_has(X86_FEATURE_HWP) dynamic check with an arch
generic CONFIG_ACPI_CPPC_LIB build-time check.

Note:
CONFIG_X86_INTEL_PSTATE selects CONFIG_ACPI_CPPC_LIB.

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
---
 drivers/acpi/bus.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

Comments

Sudeep Holla May 11, 2022, 2:22 p.m. UTC | #1
On Wed, May 11, 2022 at 03:45:56PM +0200, Pierre Gondois wrote:
> The _OSC method allows the OS and firmware to communicate about
> supported features/capabitlities. It also allows the OS to take
> control of some features.
> 
> In ACPI 6.4, s6.2.11.2 Platform-Wide OSPM Capabilities, the CPPC
> (resp. v2) bit should be set by the OS if it 'supports controlling
> processor performance via the interfaces described in the _CPC
> object'.
> 
> The OS supports CPPC and parses the _CPC object only if
> CONFIG_ACPI_CPPC_LIB is set. Replace the x86 specific
> boot_cpu_has(X86_FEATURE_HWP) dynamic check with an arch
> generic CONFIG_ACPI_CPPC_LIB build-time check.
> 
> Note:
> CONFIG_X86_INTEL_PSTATE selects CONFIG_ACPI_CPPC_LIB.

While this is work as per the spec, by not sure what kind of ACPI firmware are
in the wild. So be prepared to relax/constrain to original feature check
for x86, unfortunate but may be needed.

Anyways,

Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
diff mbox series

Patch

diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index a5d08de5d1e9..4fd0ea779441 100644
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -329,10 +329,11 @@  static void acpi_bus_osc_negotiate_platform_control(void)
 #endif
 #ifdef CONFIG_X86
 	capbuf[OSC_SUPPORT_DWORD] |= OSC_SB_GENERIC_INITIATOR_SUPPORT;
-	if (boot_cpu_has(X86_FEATURE_HWP)) {
-		capbuf[OSC_SUPPORT_DWORD] |= OSC_SB_CPC_SUPPORT;
-		capbuf[OSC_SUPPORT_DWORD] |= OSC_SB_CPCV2_SUPPORT;
-	}
+#endif
+
+#ifdef CONFIG_ACPI_CPPC_LIB
+	capbuf[OSC_SUPPORT_DWORD] |= OSC_SB_CPC_SUPPORT;
+	capbuf[OSC_SUPPORT_DWORD] |= OSC_SB_CPCV2_SUPPORT;
 #endif
 
 	capbuf[OSC_SUPPORT_DWORD] |= OSC_SB_CPC_FLEXIBLE_ADR_SP;
@@ -357,10 +358,9 @@  static void acpi_bus_osc_negotiate_platform_control(void)
 		return;
 	}
 
-#ifdef CONFIG_X86
-	if (boot_cpu_has(X86_FEATURE_HWP))
-		osc_sb_cppc_not_supported = !(capbuf_ret[OSC_SUPPORT_DWORD] &
-				(OSC_SB_CPC_SUPPORT | OSC_SB_CPCV2_SUPPORT));
+#ifdef CONFIG_ACPI_CPPC_LIB
+	osc_sb_cppc_not_supported = !(capbuf_ret[OSC_SUPPORT_DWORD] &
+			(OSC_SB_CPC_SUPPORT | OSC_SB_CPCV2_SUPPORT));
 #endif
 
 	/*