cpu/amd/car: Move AP stacks below the BSP stack to free up space

Caching SPD data during startup requires additional CAR space.
There was a large chunk of free space between the AP stack top and
the BSP stack bottom; moving the AP stacks below the BSP stack
allows this space to be utilized.

TEST: Booted ASUS KGPE-D16 with dual Opteron 6129 processors (16 cores)
and 120k of CAR.

Change-Id: I370ff368affde7061d6547527bda058b9016e977
Signed-off-by: Timothy Pearson <tpearson@raptorengineeringinc.com>
Reviewed-on: http://review.coreboot.org/10404
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins)
Tested-by: Raptor Engineering Automated Test Stand <noreply@raptorengineeringinc.com>

src/cpu/Kconfig

@@ -19,6 +19,9 @@ config DCACHE_RAM_SIZE
 config DCACHE_BSP_STACK_SIZE
 	hex
 
+config DCACHE_BSP_STACK_SLUSH
+	hex
+
 config DCACHE_AP_STACK_SIZE
 	hex
 

src/cpu/amd/car/cache_as_ram.inc

@@ -26,6 +26,7 @@
 #define CacheSize		CONFIG_DCACHE_RAM_SIZE
 #define CacheBase		(0xd0000 - CacheSize)
 #define CacheSizeBSPStack	CONFIG_DCACHE_BSP_STACK_SIZE
+#define CacheSizeBSPSlush	CONFIG_DCACHE_BSP_STACK_SLUSH
 
 /* For CAR with Fam10h. */
 #define CacheSizeAPStack	CONFIG_DCACHE_AP_STACK_SIZE
@@ -377,9 +378,17 @@ CAR_FAM10_ap:
 	/*
 	 * Need to set stack pointer for AP.
 	 * It will be from:
-	 *   CacheBase + CacheSize / 2
+	 *   CacheBase + (CacheSize - (CacheSizeBSPStack + CacheSizeBSPSlush))
 	 *   - (NodeID << CoreIDbits + CoreID) * CacheSizeAPStack
-	 * So need to get the NodeID and CoreID at first.
+	 * The spacing between the BSP stack and the top of the AP
+	 * stacks is purposefully set larger (an extra CacheSizeBSPSlush
+	 * worth of unused space) than necessary to aid debugging when
+	 * additional stack variables are added by future developers.
+	 * The extra space will allow BSP overruns to be caught by
+	 * the warning logic and easily fixed instead of crashing the
+	 * system with no obvious clues of what went wrong.
+	 *
+	 * So, need to get the NodeID and CoreID at first.
 	 * If NB_CFG bit 54 is set just use initial APIC ID, otherwise need
 	 * to reverse it.
 	 */
@@ -411,7 +420,7 @@ roll_cfg:
 	/* Calculate stack pointer. */
 	movl	$CacheSizeAPStack, %eax
 	mull	%ebx
-	movl	$(CacheBase + CacheSize / 2), %esp
+	movl	$(CacheBase + (CacheSize - (CacheSizeBSPStack + CacheSizeBSPSlush))), %esp
 	subl	%eax, %esp
 
 	/* Retrive init detected. */

src/cpu/amd/geode_gx2/Kconfig

@@ -41,6 +41,10 @@ config DCACHE_BSP_STACK_SIZE
 	hex
 	default 0x1000
 
+config DCACHE_BSP_STACK_SLUSH
+	hex
+	default 0x1000
+
 config DCACHE_AP_STACK_SIZE
 	hex
 	default 0x400

src/cpu/amd/geode_lx/Kconfig

@@ -23,6 +23,10 @@ config DCACHE_BSP_STACK_SIZE
 	hex
 	default 0x2000
 
+config DCACHE_BSP_STACK_SLUSH
+	hex
+	default 0x1000
+
 config DCACHE_AP_STACK_SIZE
 	hex
 	default 0x400

src/cpu/amd/model_10xxx/Kconfig

@@ -34,6 +34,10 @@ config DCACHE_BSP_STACK_SIZE
 	hex
 	default 0x2000
 
+config DCACHE_BSP_STACK_SLUSH
+	hex
+	default 0x1000
+
 config DCACHE_AP_STACK_SIZE
 	hex
 	default 0x400

src/cpu/amd/model_10xxx/init_cpus.c

@@ -250,8 +250,11 @@ static u32 init_cpus(u32 cpu_init_detectedx, struct sys_info *sysinfo)
 	u32 apicid;
 	struct node_core_id id;
 
+	/* Please refer to the calculations and explaination in cache_as_ram.inc before modifying these values */
 	uint32_t max_ap_stack_region_size = CONFIG_MAX_CPUS * CONFIG_DCACHE_AP_STACK_SIZE;
-	uint32_t bsp_stack_region_lower_boundary = CONFIG_DCACHE_RAM_BASE + (CONFIG_DCACHE_RAM_SIZE / 2);
+	uint32_t max_bsp_stack_region_size = CONFIG_DCACHE_BSP_STACK_SIZE + CONFIG_DCACHE_BSP_STACK_SLUSH;
+	uint32_t bsp_stack_region_upper_boundary = CONFIG_DCACHE_RAM_BASE + CONFIG_DCACHE_RAM_SIZE;
+	uint32_t bsp_stack_region_lower_boundary = bsp_stack_region_upper_boundary - max_bsp_stack_region_size;
 	void * lower_stack_region_boundary = (void*)(bsp_stack_region_lower_boundary - max_ap_stack_region_size);
 	if (((void*)(sysinfo + 1)) > lower_stack_region_boundary)
 		printk(BIOS_WARNING,

src/cpu/amd/socket_754/Kconfig

@@ -24,6 +24,10 @@ config DCACHE_BSP_STACK_SIZE
 	hex
 	default 0x2000
 
+config DCACHE_BSP_STACK_SLUSH
+	hex
+	default 0x1000
+
 config DCACHE_AP_STACK_SIZE
 	hex
 	default 0x400

src/cpu/amd/socket_940/Kconfig

@@ -25,6 +25,10 @@ config DCACHE_BSP_STACK_SIZE
 	hex
 	default 0x2000
 
+config DCACHE_BSP_STACK_SLUSH
+	hex
+	default 0x1000
+
 config DCACHE_AP_STACK_SIZE
 	hex
 	default 0x400

src/cpu/amd/socket_S1G1/Kconfig

@@ -35,6 +35,10 @@ config DCACHE_BSP_STACK_SIZE
 	hex
 	default 0x2000
 
+config DCACHE_BSP_STACK_SLUSH
+	hex
+	default 0x1000
+
 config DCACHE_AP_STACK_SIZE
 	hex
 	default 0x400