diff --git a/arch/sparc64/kernel/setup.c b/arch/sparc64/kernel/setup.c
index 12c3d84b7460cb987fc511e0675f0ef5234f58c3..b7e6a91952b213dacfe1ce43e2497df4192de634 100644
--- a/arch/sparc64/kernel/setup.c
+++ b/arch/sparc64/kernel/setup.c
@@ -383,6 +383,17 @@ static void __init process_switch(char c)
 		/* Use PROM debug console. */
 		register_console(&prom_debug_console);
 		break;
+	case 'P':
+		/* Force UltraSPARC-III P-Cache on. */
+		if (tlb_type != cheetah) {
+			printk("BOOT: Ignoring P-Cache force option.\n");
+			break;
+		}
+		cheetah_pcache_forced_on = 1;
+		add_taint(TAINT_MACHINE_CHECK);
+		cheetah_enable_pcache();
+		break;
+
 	default:
 		printk("Unknown boot switch (-%c)\n", c);
 		break;
diff --git a/arch/sparc64/kernel/smp.c b/arch/sparc64/kernel/smp.c
index 6dff06a44e76ed4730d6919fb0c09f3f044f8a42..e5b9c7a27789853d13c6e350afabdfb123092373 100644
--- a/arch/sparc64/kernel/smp.c
+++ b/arch/sparc64/kernel/smp.c
@@ -123,6 +123,9 @@ void __init smp_callin(void)
 
 	smp_setup_percpu_timer();
 
+	if (cheetah_pcache_forced_on)
+		cheetah_enable_pcache();
+
 	local_irq_enable();
 
 	calibrate_delay();
diff --git a/arch/sparc64/kernel/traps.c b/arch/sparc64/kernel/traps.c
index 56b203a2af696e43491e8e4dba0057daa72b95db..a9f4596d7c2bcd82419386d808b5f35d69d2a46a 100644
--- a/arch/sparc64/kernel/traps.c
+++ b/arch/sparc64/kernel/traps.c
@@ -421,6 +421,25 @@ asmlinkage void cee_log(unsigned long ce_status,
 	}
 }
 
+int cheetah_pcache_forced_on;
+
+void cheetah_enable_pcache(void)
+{
+	unsigned long dcr;
+
+	printk("CHEETAH: Enabling P-Cache on cpu %d.\n",
+	       smp_processor_id());
+
+	__asm__ __volatile__("ldxa [%%g0] %1, %0"
+			     : "=r" (dcr)
+			     : "i" (ASI_DCU_CONTROL_REG));
+	dcr |= (DCU_PE | DCU_HPE | DCU_SPE | DCU_SL);
+	__asm__ __volatile__("stxa %0, [%%g0] %1\n\t"
+			     "membar #Sync"
+			     : /* no outputs */
+			     : "r" (dcr), "i" (ASI_DCU_CONTROL_REG));
+}
+
 /* Cheetah error trap handling. */
 static unsigned long ecache_flush_physbase;
 static unsigned long ecache_flush_linesize;
diff --git a/include/asm-sparc64/spitfire.h b/include/asm-sparc64/spitfire.h
index ad78ce64d69ee8f04f35e03301826b74c42b5298..9d7613eea8129a58dbbcca8dbaef05f2228f6d66 100644
--- a/include/asm-sparc64/spitfire.h
+++ b/include/asm-sparc64/spitfire.h
@@ -48,6 +48,9 @@ enum ultra_tlb_layout {
 
 extern enum ultra_tlb_layout tlb_type;
 
+extern int cheetah_pcache_forced_on;
+extern void cheetah_enable_pcache(void);
+
 #define sparc64_highest_locked_tlbent()	\
 	(tlb_type == spitfire ? \
 	 SPITFIRE_HIGHEST_LOCKED_TLBENT : \