arch/i386/kernel/cpu/amd.c

#include <linux/init.h>
#include <linux/bitops.h>
#include <linux/mm.h>
#include <asm/io.h>
#include <asm/processor.h>

#include "cpu.h"

/*
 *	B step AMD K6 before B 9730xxxx have hardware bugs that can cause
 *	misexecution of code under Linux. Owners of such processors should
 *	contact AMD for precise details and a CPU swap.
 *
 *	See	http://www.multimania.com/poulot/k6bug.html
 *		http://www.amd.com/K6/k6docs/revgd.html
 *
 *	The following test is erm.. interesting. AMD neglected to up
 *	the chip setting when fixing the bug but they also tweaked some
 *	performance at the same time..
 */
 
extern void vide(void);
__asm__(".align 4\nvide: ret");

static void __init init_amd(struct cpuinfo_x86 *c)
{
	u32 l, h;
	int mbytes = num_physpages >> (20-PAGE_SHIFT);
	int r;

	/*
	 *	FIXME: We should handle the K5 here. Set up the write
	 *	range and also turn on MSR 83 bits 4 and 31 (write alloc,
	 *	no bus pipeline)
	 */

	/* Bit 31 in normal CPUID used for nonstandard 3DNow ID;
	   3DNow is IDd by bit 31 in extended CPUID (1*32+31) anyway */
	clear_bit(0*32+31, c->x86_capability);
	
	r = get_model_name(c);

	switch(c->x86)
	{
		case 4:
		/*
		 * General Systems BIOSen alias the cpu frequency registers
		 * of the Elan at 0x000df000. Unfortuantly, one of the Linux
		 * drivers subsequently pokes it, and changes the CPU speed.
		 * Workaround : Remove the unneeded alias.
		 */
#define CBAR		(0xfffc) /* Configuration Base Address  (32-bit) */
#define CBAR_ENB	(0x80000000)
#define CBAR_KEY	(0X000000CB)
			if (c->x86_model==9 || c->x86_model == 10) {
				if (inl (CBAR) & CBAR_ENB)
					outl (0 | CBAR_KEY, CBAR);
			}
			break;
		case 5:
			if( c->x86_model < 6 )
			{
				/* Based on AMD doc 20734R - June 2000 */
				if ( c->x86_model == 0 ) {
					clear_bit(X86_FEATURE_APIC, c->x86_capability);
					set_bit(X86_FEATURE_PGE, c->x86_capability);
				}
				break;
			}
			
			if ( c->x86_model == 6 && c->x86_mask == 1 ) {
				const int K6_BUG_LOOP = 1000000;
				int n;
				void (*f_vide)(void);
				unsigned long d, d2;
				
				printk(KERN_INFO "AMD K6 stepping B detected - ");
				
				/*
				 * It looks like AMD fixed the 2.6.2 bug and improved indirect 
				 * calls at the same time.
				 */

				n = K6_BUG_LOOP;
				f_vide = vide;
				rdtscl(d);
				while (n--) 
					f_vide();
				rdtscl(d2);
				d = d2-d;
				
				/* Knock these two lines out if it debugs out ok */
				printk(KERN_INFO "AMD K6 stepping B detected - ");
				/* -- cut here -- */
				if (d > 20*K6_BUG_LOOP) 
					printk("system stability may be impaired when more than 32 MB are used.\n");
				else 
					printk("probably OK (after B9730xxxx).\n");
				printk(KERN_INFO "Please see http://membres.lycos.fr/poulot/k6bug.html\n");
			}

			/* K6 with old style WHCR */
			if (c->x86_model < 8 ||
			   (c->x86_model== 8 && c->x86_mask < 8)) {
				/* We can only write allocate on the low 508Mb */
				if(mbytes>508)
					mbytes=508;

				rdmsr(MSR_K6_WHCR, l, h);
				if ((l&0x0000FFFF)==0) {
					unsigned long flags;
					l=(1<<0)|((mbytes/4)<<1);
					local_irq_save(flags);
					wbinvd();
					wrmsr(MSR_K6_WHCR, l, h);
					local_irq_restore(flags);
					printk(KERN_INFO "Enabling old style K6 write allocation for %d Mb\n",
						mbytes);
				}
				break;
			}

			if ((c->x86_model == 8 && c->x86_mask >7) ||
			     c->x86_model == 9 || c->x86_model == 13) {
				/* The more serious chips .. */

				if(mbytes>4092)
					mbytes=4092;

				rdmsr(MSR_K6_WHCR, l, h);
				if ((l&0xFFFF0000)==0) {
					unsigned long flags;
					l=((mbytes>>2)<<22)|(1<<16);
					local_irq_save(flags);
					wbinvd();
					wrmsr(MSR_K6_WHCR, l, h);
					local_irq_restore(flags);
					printk(KERN_INFO "Enabling new style K6 write allocation for %d Mb\n",
						mbytes);
				}

				/*  Set MTRR capability flag if appropriate */
				if (c->x86_model == 13 || c->x86_model == 9 ||
				   (c->x86_model == 8 && c->x86_mask >= 8))
					set_bit(X86_FEATURE_K6_MTRR, c->x86_capability);
				break;
			}
			break;

		case 6: /* An Athlon/Duron */
 
			/* Bit 15 of Athlon specific MSR 15, needs to be 0
 			 * to enable SSE on Palomino/Morgan/Barton CPU's.
			 * If the BIOS didn't enable it already, enable it here.
			 */
			if (c->x86_model >= 6 && c->x86_model <= 10) {
				if (!cpu_has(c, X86_FEATURE_XMM)) {
					printk(KERN_INFO "Enabling disabled K7/SSE Support.\n");
					rdmsr(MSR_K7_HWCR, l, h);
					l &= ~0x00008000;
					wrmsr(MSR_K7_HWCR, l, h);
					set_bit(X86_FEATURE_XMM, c->x86_capability);
				}
			}

			/* It's been determined by AMD that Athlons since model 8 stepping 1
			 * are more robust with CLK_CTL set to 200xxxxx instead of 600xxxxx
			 * As per AMD technical note 27212 0.2
			 */
			if ((c->x86_model == 8 && c->x86_mask>=1) || (c->x86_model > 8)) {
				rdmsr(MSR_K7_CLK_CTL, l, h);
				if ((l & 0xfff00000) != 0x20000000) {
					printk ("CPU: CLK_CTL MSR was %x. Reprogramming to %x\n", l,
						((l & 0x000fffff)|0x20000000));
					wrmsr(MSR_K7_CLK_CTL, (l & 0x000fffff)|0x20000000, h);
				}
			}
			break;
	}

	switch (c->x86) {
	case 15:
		set_bit(X86_FEATURE_K8, c->x86_capability);
		break;
	case 6:
		set_bit(X86_FEATURE_K7, c->x86_capability); 
		break;
	}

	display_cacheinfo(c);
	detect_ht(c);

#ifdef CONFIG_X86_HT
	/* AMD dual core looks like HT but isn't really. Hide it from the
	   scheduler. This works around problems with the domain scheduler.
	   Also probably gives slightly better scheduling and disables
	   SMT nice which is harmful on dual core.
	   TBD tune the domain scheduler for dual core. */
	if (cpu_has(c, X86_FEATURE_CMP_LEGACY))
		smp_num_siblings = 1;
#endif

	if (cpuid_eax(0x80000000) >= 0x80000008) {
		c->x86_num_cores = (cpuid_ecx(0x80000008) & 0xff) + 1;
		if (c->x86_num_cores & (c->x86_num_cores - 1))
			c->x86_num_cores = 1;
	}
}

static unsigned int amd_size_cache(struct cpuinfo_x86 * c, unsigned int size)
{
	/* AMD errata T13 (order #21922) */
	if ((c->x86 == 6)) {
		if (c->x86_model == 3 && c->x86_mask == 0)	/* Duron Rev A0 */
			size = 64;
		if (c->x86_model == 4 &&
		    (c->x86_mask==0 || c->x86_mask==1))	/* Tbird rev A1/A2 */
			size = 256;
	}
	return size;
}

static struct cpu_dev amd_cpu_dev __initdata = {
	.c_vendor	= "AMD",
	.c_ident 	= { "AuthenticAMD" },
	.c_models = {
		{ .vendor = X86_VENDOR_AMD, .family = 4, .model_names =
		  {
			  [3] = "486 DX/2",
			  [7] = "486 DX/2-WB",
			  [8] = "486 DX/4", 
			  [9] = "486 DX/4-WB", 
			  [14] = "Am5x86-WT",
			  [15] = "Am5x86-WB" 
		  }
		},
	},
	.c_init		= init_amd,
	.c_identify	= generic_identify,
	.c_size_cache	= amd_size_cache,
};

int __init amd_init_cpu(void)
{
	cpu_devs[X86_VENDOR_AMD] = &amd_cpu_dev;
	return 0;
}

//early_arch_initcall(amd_init_cpu);