linux-kernel - [PATCH v2] cpufreq: intel_pstate: Add additional OOB enabling bit

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Message-Id: <20200612180957.1018235-1-srinivas.pandruvada@linux.intel.com>
Date:   Fri, 12 Jun 2020 11:09:57 -0700
From:   Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To:     rjw@...ysocki.net, lenb@...nel.org, viresh.kumar@...aro.org,
        dsmythies@...us.net
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: [PATCH v2] cpufreq: intel_pstate: Add additional OOB enabling bit

Add additional bit for OOB (Out of band) enabling of P-states. In this
case intel_pstate shouldn't load. Currently, only "BIT(8) == 1" of the
MSR MSR_MISC_PWR_MGMT is considered as OOB. Also add "BIT(18) == 1" as
OOB condition.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
---
v2
   - As suggested by Doug add OOB in debug message
   - Atleast added local definition of OOB mask

 drivers/cpufreq/intel_pstate.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 8e23a698ce04..4e9bfd2509b8 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -2677,6 +2677,7 @@ static struct acpi_platform_list plat_info[] __initdata = {
 	{ } /* End */
 };
 
+#define BITMASK_OOB	(BIT(8) | BIT(18))
 static bool __init intel_pstate_platform_pwr_mgmt_exists(void)
 {
 	const struct x86_cpu_id *id;
@@ -2686,8 +2687,9 @@ static bool __init intel_pstate_platform_pwr_mgmt_exists(void)
 	id = x86_match_cpu(intel_pstate_cpu_oob_ids);
 	if (id) {
 		rdmsrl(MSR_MISC_PWR_MGMT, misc_pwr);
-		if (misc_pwr & (1 << 8)) {
-			pr_debug("Bit 8 in the MISC_PWR_MGMT MSR set\n");
+		if (misc_pwr & BITMASK_OOB) {
+			pr_debug("Bit 8 or 18 in the MISC_PWR_MGMT MSR set\n");
+			pr_debug("P states are controlled in Out of Band mode by the firmware/hardware\n");
 			return true;
 		}
 	}
-- 
2.24.1