From bb83e857a2e7b6ecb7cb476ba65019b14e68dc34 Mon Sep 17 00:00:00 2001
From: Leah Rowe <leah@libreboot.org>
Date: Wed, 1 Dec 2021 02:53:00 +0000
Subject: [PATCH 16/30] fix speedstep on x200/t400: Revert
 "cpu/intel/model_1067x: enable PECI"

This reverts commit 70fea013c7ebd6d85a7806748233fcfd76802f5f.

Enabling PECI without microcode updates loaded causes the CPUID feature set
to become corrupted. And one consequence is broken SpeedStep. At least, that's
my understanding looking at Intel Errata. This revert is not a fix, because
upstream is correct (upstream assumes microcode updates). We will simply
maintain this revert patch in Libreboot, from now on.
---
 src/cpu/intel/model_1067x/model_1067x_init.c | 9 ---------
 1 file changed, 9 deletions(-)

diff --git a/src/cpu/intel/model_1067x/model_1067x_init.c b/src/cpu/intel/model_1067x/model_1067x_init.c
index 315e7c36fc..1423fd72bc 100644
--- a/src/cpu/intel/model_1067x/model_1067x_init.c
+++ b/src/cpu/intel/model_1067x/model_1067x_init.c
@@ -141,8 +141,6 @@ static void configure_emttm_tables(void)
 	wrmsr(MSR_EMTTM_CR_TABLE(5), msr);
 }
 
-#define IA32_PECI_CTL		0x5a0
-
 static void configure_misc(const int eist, const int tm2, const int emttm)
 {
 	msr_t msr;
@@ -185,13 +183,6 @@ static void configure_misc(const int eist, const int tm2, const int emttm)
 		msr.lo |= (1 << 20);	/* Lock Enhanced SpeedStep Enable */
 		wrmsr(IA32_MISC_ENABLE, msr);
 	}
-
-	/* Enable PECI
-	   WARNING: due to Erratum AW67 described in Intel document #318733
-	   the microcode must be updated before this MSR is written to. */
-	msr = rdmsr(IA32_PECI_CTL);
-	msr.lo |= 1;
-	wrmsr(IA32_PECI_CTL, msr);
 }
 
 #define PIC_SENS_CFG	0x1aa
-- 
2.39.2

