northbridge/amd/amdht: Allow mainboards to set HT frequency limit

This is useful when the PCB layout of a mainboard does not allow
stable operation at the increased HyperTransport speeds of newer
processors.

Change-Id: Idc93a1294608178ddf38ca72d40e6bad7deb9004
Signed-off-by: Timothy Pearson <tpearson@raptorengineeringinc.com>
Reviewed-on: http://review.coreboot.org/8464
Tested-by: build bot (Jenkins)
Reviewed-by: Marc Jones <marc.jones@se-eng.com>

src/northbridge/amd/amdfam10/amdfam10.h

@@ -1,6 +1,7 @@
 /*
  * This file is part of the coreboot project.
  *
+ * Copyright (C) 2015 Timothy Pearson <tpearson@raptorengineeringinc.com>, Raptor Engineering
  * Copyright (C) 2007 Advanced Micro Devices, Inc.
  *
  * This program is free software; you can redistribute it and/or modify
@@ -1002,6 +1003,10 @@ struct nodes_info_t {
 	u32 up_planes; // down planes will be [up_planes, planes)
 } __attribute__((packed));
 
+struct ht_link_config {
+	uint8_t ht_speed_limit; // Speed in MHz; 0 for autodetect (default)
+};
+
 /* be careful with the alignment of sysinfo, bacause sysinfo may be shared by coreboot_car and ramstage stage. and ramstage may be running at 64bit later.*/
 
 struct sys_info {
@@ -1015,6 +1020,8 @@ struct sys_info {
 	u8 host_link_freq[NODE_NUMS*8]; // record freq for every link from cpu, 0x0f means don't need to touch it
 	u16 host_link_freq_cap[NODE_NUMS*8]; //cap
 
+	struct ht_link_config ht_link_cfg;
+
 	u32 segbit;
 	u32 sbdn;
 	u32 sblk;

src/northbridge/amd/amdht/h3finit.c

@@ -75,6 +75,41 @@ static const uint16_t ht_speed_limit[16] =
 	 0x00FF, 0x007F, 0x003F, 0x001F,
 	 0x000F, 0x0007, 0x0003, 0x0001};
 
+static const struct ht_speed_limit_map_t {
+	uint16_t mhz;
+	uint8_t config;
+} ht_speed_limit_map[] = {
+	{0, NVRAM_LIMIT_HT_SPEED_AUTO},
+	{200, NVRAM_LIMIT_HT_SPEED_200},
+	{300, NVRAM_LIMIT_HT_SPEED_300},
+	{400, NVRAM_LIMIT_HT_SPEED_400},
+	{500, NVRAM_LIMIT_HT_SPEED_500},
+	{600, NVRAM_LIMIT_HT_SPEED_600},
+	{800, NVRAM_LIMIT_HT_SPEED_800},
+	{1000, NVRAM_LIMIT_HT_SPEED_1000},
+	{1200, NVRAM_LIMIT_HT_SPEED_1200},
+	{1400, NVRAM_LIMIT_HT_SPEED_1400},
+	{1600, NVRAM_LIMIT_HT_SPEED_1600},
+	{1800, NVRAM_LIMIT_HT_SPEED_1800},
+	{2000, NVRAM_LIMIT_HT_SPEED_2000},
+	{2200, NVRAM_LIMIT_HT_SPEED_2200},
+	{2400, NVRAM_LIMIT_HT_SPEED_2400},
+	{2600, NVRAM_LIMIT_HT_SPEED_2600},
+};
+
+static const uint16_t ht_speed_mhz_to_hw(uint16_t mhz)
+{
+	size_t i;
+	for (i = 0; i < ARRAY_SIZE(ht_speed_limit_map); i++)
+		if (ht_speed_limit_map[i].mhz == mhz)
+			return ht_speed_limit_map[i].config;
+
+	printk(BIOS_WARNING,
+		"WARNING: Invalid HT link limit frequency %d specified, ignoring...\n",
+		 mhz);
+	return ht_speed_limit[NVRAM_LIMIT_HT_SPEED_AUTO];
+}
+
 /*----------------------------------------------------------------------------
  *			TYPEDEFS AND STRUCTURES
  *
@@ -1359,10 +1394,9 @@ static void selectOptimalWidthAndFrequency(sMainData *pDat)
 
 	for (i = 0; i < pDat->TotalLinks*2; i += 2)
 	{
-		/* FIXME
-		 * Mainboards need to be able to set cbPCBFreqLimit
-		 */
 		cbPCBFreqLimit = 0xFFFF;		// Maximum allowed by autoconfiguration
+		if (pDat->HtBlock->ht_link_configuration)
+			cbPCBFreqLimit = ht_speed_mhz_to_hw(pDat->HtBlock->ht_link_configuration->ht_speed_limit);
 		cbPCBFreqLimit = min(cbPCBFreqLimit, cbPCBFreqLimit_NVRAM);
 
 #if CONFIG_EXPERT && CONFIG_LIMIT_HT_DOWN_WIDTH_8

src/northbridge/amd/amdht/h3finit.h

@@ -1,6 +1,7 @@
 /*
  * This file is part of the coreboot project.
  *
+ * Copyright (C) 2015 Timothy Pearson <tpearson@raptorengineeringinc.com>, Raptor Engineering
  * Copyright (C) 2007 Advanced Micro Devices, Inc.
  *
  * This program is free software; you can redistribute it and/or modify
@@ -462,6 +463,8 @@ typedef struct {
 		const u8 *pEventData0
 	);
 
+	const struct ht_link_config *ht_link_configuration;
+
 } AMD_HTBLOCK;
 
 /*

src/northbridge/amd/amdht/ht_wrapper.c

@@ -139,7 +139,8 @@ static void amd_ht_init(struct sys_info *sysinfo)
 		NULL,	// BOOL (*AMD_CB_CustomizeBuffers)();
 		NULL,	// void (*AMD_CB_OverrideDevicePort)();
 		NULL,	// void (*AMD_CB_OverrideCpuPort)();
-		AMD_CB_EventNotify	// void (*AMD_CB_EventNotify) ();
+		AMD_CB_EventNotify,	// void (*AMD_CB_EventNotify) ();
+		&sysinfo->ht_link_cfg // struct ht_link_config*
 	};
 
 	printk(BIOS_DEBUG, "Enter amd_ht_init()\n");