CPU: Set flex ratio to nominal TDP ratio in bootblock

CPUs with configurable TDP will run the TSC at the max non-turbo
ratio for the maximum TDP value, which can cause issues if another
TDP is desired.  To deal with this we set the flex ratio to the
nominal TDP ratio early in the boot and then configure the Soft
Reset Data registers so the PCH can tell the CPU what frequency
to run at after a reset.

This is done very early in the bootblock because it is necessary
to reset the system after setting a flex ratio.

The end result is that the TSC will now increment at the max
non-turbo frequency for the nominal TDP.

On some system with 1.8GHz CPU ensure that the kernel
detects the CPU speed as ~1800mhz rather than ~2300mhz:

> dmesg | grep "MHz processor"
[    0.004000] Detected 1795.801 MHz processor.

Change-Id: I8436dced9199003b6423186a2b041e3f7b84ab8c
Signed-off-by: Duncan Laurie <dlaurie@google.com>
Reviewed-on: http://review.coreboot.org/1329
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

1 files changed, 62 insertions, 0 deletions

diff --git a/src/cpu/intel/model_206ax/bootblock.c b/src/cpu/intel/model_206ax/bootblock.c
index 4061bb7b5a..dbc35914cb 100644
--- a/src/cpu/intel/model_206ax/bootblock.c
+++ b/src/cpu/intel/model_206ax/bootblock.c
@@ -22,6 +22,8 @@
 #include <cpu/x86/cache.h>
 #include <cpu/x86/msr.h>
 #include <cpu/x86/mtrr.h>
+#include <arch/io.h>
+#include <arch/romcc_io.h>
 
 #if !CONFIG_MICROCODE_IN_CBFS
 static const uint32_t microcode_updates[] = {
@@ -30,6 +32,14 @@ static const uint32_t microcode_updates[] = {
 #endif
 
 #include <cpu/intel/microcode/microcode.c>
+#include "model_206ax.h"
+
+#if CONFIG_SOUTHBRIDGE_INTEL_BD82X6X || CONFIG_SOUTHBRIDGE_INTEL_C216
+/* Needed for RCBA access to set Soft Reset Data register */
+#include <southbridge/intel/bd82x6x/pch.h>
+#else
+#error "CPU must be paired with Intel BD82X6X or C216 southbridge"
+#endif
 
 static void set_var_mtrr(
 	unsigned reg, unsigned base, unsigned size, unsigned type)
@@ -60,8 +70,60 @@ static void enable_rom_caching(void)
 	wrmsr(MTRRdefType_MSR, msr);
 }
 
+static void set_flex_ratio_to_tdp_nominal(void)
+{
+	msr_t flex_ratio, msr;
+	u32 soft_reset;
+	u8 nominal_ratio;
+
+	/* Minimum CPU revision for configurable TDP support */
+	if (cpuid_eax(1) < IVB_CONFIG_TDP_MIN_CPUID)
+		return;
+
+	/* Check for Flex Ratio support */
+	flex_ratio = rdmsr(MSR_FLEX_RATIO);
+	if (!(flex_ratio.lo & FLEX_RATIO_EN))
+		return;
+
+	/* Check for >0 configurable TDPs */
+	msr = rdmsr(MSR_PLATFORM_INFO);
+	if (((msr.hi >> 1) & 3) == 0)
+		return;
+
+	/* Use nominal TDP ratio for flex ratio */
+	msr = rdmsr(MSR_CONFIG_TDP_NOMINAL);
+	nominal_ratio = msr.lo & 0xff;
+
+	/* See if flex ratio is already set to nominal TDP ratio */
+	if (((flex_ratio.lo >> 8) & 0xff) == nominal_ratio)
+		return;
+
+	/* Set flex ratio to nominal TDP ratio */
+	flex_ratio.lo &= ~0xff00;
+	flex_ratio.lo |= nominal_ratio << 8;
+	flex_ratio.lo |= FLEX_RATIO_LOCK;
+	wrmsr(MSR_FLEX_RATIO, flex_ratio);
+
+	/* Set flex ratio in soft reset data register bits 11:6.
+	 * RCBA region is enabled in southbridge bootblock */
+	soft_reset = RCBA32(SOFT_RESET_DATA);
+	soft_reset &= ~(0x3f << 6);
+	soft_reset |= (nominal_ratio & 0x3f) << 6;
+	RCBA32(SOFT_RESET_DATA) = soft_reset;
+
+	/* Set soft reset control to use register value */
+	RCBA32_OR(SOFT_RESET_CTRL, 1);
+
+	/* Issue warm reset, will be "CPU only" due to soft reset data */
+	outb(0x0, 0xcf9);
+	outb(0x6, 0xcf9);
+	asm("hlt");
+}
+
 static void bootblock_cpu_init(void)
 {
+	/* Set flex ratio and reset if needed */
+	set_flex_ratio_to_tdp_nominal();
 	enable_rom_caching();
 #if CONFIG_MICROCODE_IN_CBFS
 	intel_update_microcode_from_cbfs();