xtensa: add SMP support

This is largely based on SMP code from the xtensa-2.6.29-smp tree by
Piet Delaney, Marc Gauthier, Joe Taylor, Christian Zankel (and possibly
other Tensilica folks).

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

1 files changed, 87 insertions, 43 deletions

diff --git a/arch/xtensa/kernel/head.S b/arch/xtensa/kernel/head.S
index 7d740ebbe198..74ec62c892bc 100644
--- a/arch/xtensa/kernel/head.S
+++ b/arch/xtensa/kernel/head.S
@@ -19,6 +19,7 @@
 #include <asm/page.h>
 #include <asm/cacheasm.h>
 #include <asm/initialize_mmu.h>
+#include <asm/mxregs.h>
 
 #include <linux/init.h>
 #include <linux/linkage.h>
@@ -54,7 +55,7 @@ ENTRY(_start)
 
 	/* Preserve the pointer to the boot parameter list in EXCSAVE_1 */
 	wsr     a2, excsave1
-	_j	_SetupMMU
+	_j	_SetupOCD
 
 	.align	4
 	.literal_position
@@ -62,6 +63,23 @@ ENTRY(_start)
 	.word	_startup
 
 	.align	4
+_SetupOCD:
+	/*
+	 * Initialize WB, WS, and clear PS.EXCM (to allow loop instructions).
+	 * Set Interrupt Level just below XCHAL_DEBUGLEVEL to allow
+	 * xt-gdb to single step via DEBUG exceptions received directly
+	 * by ocd.
+	 */
+	movi	a1, 1
+	movi	a0, 0
+	wsr	a1, windowstart
+	wsr	a0, windowbase
+	rsync
+
+	movi	a1, LOCKLEVEL
+	wsr	a1, ps
+	rsync
+
 	.global _SetupMMU
 _SetupMMU:
 	Offset = _SetupMMU - _start
@@ -90,19 +108,6 @@ ENDPROC(_start)
 
 ENTRY(_startup)
 
-	/* Disable interrupts and exceptions. */
-
-	movi	a0, LOCKLEVEL
-	wsr	a0, ps
-
-	/* Start with a fresh windowbase and windowstart.  */
-
-	movi	a1, 1
-	movi	a0, 0
-	wsr	a1, windowstart
-	wsr	a0, windowbase
-	rsync
-
 	/* Set a0 to 0 for the remaining initialization. */
 
 	movi	a0, 0
@@ -154,17 +159,6 @@ ENTRY(_startup)
 	wsr	a0, cpenable
 #endif
 
-	/* Set PS.INTLEVEL=LOCKLEVEL, PS.WOE=0, kernel stack, PS.EXCM=0
-	 *
-	 * Note: PS.EXCM must be cleared before using any loop
-	 *	 instructions; otherwise, they are silently disabled, and
-	 * 	 at most one iteration of the loop is executed.
-	 */
-
-	movi	a1, LOCKLEVEL
-	wsr	a1, ps
-	rsync
-
 	/*  Initialize the caches.
 	 *  a2, a3 are just working registers (clobbered).
 	 */
@@ -182,6 +176,37 @@ ENTRY(_startup)
 
 	isync
 
+#ifdef CONFIG_HAVE_SMP
+	movi	a2, CCON	# MX External Register to Configure Cache
+	movi	a3, 1
+	wer	a3, a2
+#endif
+
+	/* Setup stack and enable window exceptions (keep irqs disabled) */
+
+	movi	a1, start_info
+	l32i	a1, a1, 0
+
+	movi	a2, (1 << PS_WOE_BIT) | LOCKLEVEL
+					# WOE=1, INTLEVEL=LOCKLEVEL, UM=0
+	wsr	a2, ps			# (enable reg-windows; progmode stack)
+	rsync
+
+	/* Set up EXCSAVE[DEBUGLEVEL] to point to the Debug Exception Handler.*/
+
+	movi	a2, debug_exception
+	wsr	a2, SREG_EXCSAVE + XCHAL_DEBUGLEVEL
+
+#ifdef CONFIG_SMP
+	/*
+	 * Notice that we assume with SMP that cores have PRID
+	 * supported by the cores.
+	 */
+	rsr	a2, prid
+	bnez	a2, .Lboot_secondary
+
+#endif  /* CONFIG_SMP */
+
 	/* Unpack data sections
 	 *
 	 * The linker script used to build the Linux kernel image
@@ -234,24 +259,7 @@ ENTRY(_startup)
 	___invalidate_icache_all a2 a3
 	isync
 
-	/* Setup stack and enable window exceptions (keep irqs disabled) */
-
-	movi	a1, init_thread_union
-	addi	a1, a1, KERNEL_STACK_SIZE
-
-	movi	a2, (1 << PS_WOE_BIT) | LOCKLEVEL
-					# WOE=1, INTLEVEL=LOCKLEVEL, UM=0
-	wsr	a2, ps			# (enable reg-windows; progmode stack)
-	rsync
-
-	/* Set up EXCSAVE[DEBUGLEVEL] to point to the Debug Exception Handler.*/
-
-	movi	a2, debug_exception
-	wsr	a2, SREG_EXCSAVE + XCHAL_DEBUGLEVEL
-
-	/* Set up EXCSAVE[1] to point to the exc_table. */
-
-	movi	a6, exc_table
+	movi	a6, 0
 	xsr	a6, excsave1
 
 	/* init_arch kick-starts the linux kernel */
@@ -265,9 +273,45 @@ ENTRY(_startup)
 should_never_return:
 	j	should_never_return
 
+#ifdef CONFIG_SMP
+.Lboot_secondary:
+
+	movi	a2, cpu_start_ccount
+1:
+	l32i	a3, a2, 0
+	beqi	a3, 0, 1b
+	movi	a3, 0
+	s32i	a3, a2, 0
+	memw
+1:
+	l32i	a3, a2, 0
+	beqi	a3, 0, 1b
+	wsr	a3, ccount
+	movi	a3, 0
+	s32i	a3, a2, 0
+	memw
+
+	movi	a6, 0
+	wsr	a6, excsave1
+
+	movi	a4, secondary_start_kernel
+	callx4	a4
+	j	should_never_return
+
+#endif  /* CONFIG_SMP */
+
 ENDPROC(_startup)
 
 /*
+ * DATA section
+ */
+
+        .section ".data.init.refok"
+        .align  4
+ENTRY(start_info)
+        .long   init_thread_union + KERNEL_STACK_SIZE
+
+/*
  * BSS section
  */