linux-kernel - [RFC PATCH 2/4] cpufreq: acpi-cpufreq: Add processor to the ignore PSD override list

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Message-Id: <20201125144847.3920-3-punitagrawal@gmail.com>
Date:   Wed, 25 Nov 2020 23:48:45 +0900
From:   Punit Agrawal <punitagrawal@...il.com>
To:     rjw@...ysocki.net
Cc:     Punit Agrawal <punitagrawal@...il.com>, wei.huang2@....com,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        bp@...en8.de, x86@...nel.org
Subject: [RFC PATCH 2/4] cpufreq: acpi-cpufreq: Add processor to the ignore PSD override list

Booting Linux on a Zen2 based processor (family: 0x17, model: 0x60,
stepping: 0x1) shows the following message in the logs -

    acpi_cpufreq: overriding BIOS provided _PSD data

Although commit 5368512abe08 ("acpi-cpufreq: Honor _PSD table setting
on new AMD CPUs") indicates that the override is not required for Zen3
onwards, it seems that domain information can be trusted even on
certain earlier systems. Update the check, to skip the override for
Zen2 processors known to work without the override.

Signed-off-by: Punit Agrawal <punitagrawal@...il.com>
Cc: Wei Huang <wei.huang2@....com>
---
 drivers/cpufreq/acpi-cpufreq.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
index b1e7df96d428..29f1cd93541e 100644
--- a/drivers/cpufreq/acpi-cpufreq.c
+++ b/drivers/cpufreq/acpi-cpufreq.c
@@ -198,8 +198,13 @@ static int override_acpi_psd(unsigned int cpu_id)
 	if (c->x86_vendor == X86_VENDOR_AMD) {
 		if (!check_amd_hwpstate_cpu(cpu_id))
 			return false;
-
-		return c->x86 < 0x19;
+		/*
+		 * CPU's before Zen3 (except some Zen2) need the
+		 * override.
+		 */
+		return (c->x86 < 0x19) &&
+			!(c->x86 == 0x17 && c->x86_model == 0x60 &&
+			  c->x86_stepping == 0x1);
 	}
 
 	return false;
-- 
2.29.2