ARC: boot: Support Halt-on-reset and Run-on-reset SMP booting modes

For Run-on-reset, non masters need to spin wait. For Halt-on-reset they
can jump to entry point directly.

Also while at it, made reset vector handler as "the" entry point for
kernel including host debugger based boot (which uses the ELF header
entry point)

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

5 files changed, 42 insertions, 29 deletions

diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index f50ff986ed60..cc938967282b 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -194,6 +194,16 @@ config NR_CPUS
         range 2 4096
         default "4"
 
+config ARC_SMP_HALT_ON_RESET
+        bool "Enable Halt-on-reset boot mode"
+        default y if ARC_UBOOT_SUPPORT
+        help
+          In SMP configuration cores can be configured as Halt-on-reset
+          or they could all start at same time. For Halt-on-reset, non
+          masters are parked until Master kicks them so they can start of
+          at designated entry point. For other case, all jump to common
+          entry point and spin wait for Master's signal.
+
 endif   #SMP
 
 menuconfig ARC_CACHE
diff --git a/arch/arc/kernel/entry-arcv2.S b/arch/arc/kernel/entry-arcv2.S
index 8fa76567e402..445e63a10754 100644
--- a/arch/arc/kernel/entry-arcv2.S
+++ b/arch/arc/kernel/entry-arcv2.S
@@ -24,7 +24,7 @@
         .align 4
 
 # Initial 16 slots are Exception Vectors
-VECTOR  stext                   ; Restart Vector (jump to entry point)
+VECTOR  res_service             ; Reset Vector
 VECTOR  mem_service             ; Mem exception
 VECTOR  instr_service           ; Instrn Error
 VECTOR  EV_MachineCheck         ; Fatal Machine check
diff --git a/arch/arc/kernel/entry-compact.S b/arch/arc/kernel/entry-compact.S
index 5221f194602b..59f52035b4ea 100644
--- a/arch/arc/kernel/entry-compact.S
+++ b/arch/arc/kernel/entry-compact.S
@@ -86,7 +86,7 @@
  */
 
 ; ********* Critical System Events **********************
-VECTOR   res_service             ; 0x0, Restart Vector  (0x0)
+VECTOR   res_service             ; 0x0, Reset Vector    (0x0)
 VECTOR   mem_service             ; 0x8, Mem exception   (0x1)
 VECTOR   instr_service           ; 0x10, Instrn Error   (0x2)
 
@@ -155,13 +155,9 @@ int2_saved_reg:
 ; ---------------------------------------------
         .section .text, "ax",@progbits
 
-res_service:            ; processor restart
-        flag    0x1     ; not implemented
-        nop
-        nop
 
-reserved:               ; processor restart
-        rtie            ; jump to processor initializations
+reserved:
+        flag 1          ; Unexpected event, halt
 
 ;##################### Interrupt Handling ##############################
 
diff --git a/arch/arc/kernel/head.S b/arch/arc/kernel/head.S
index 812f95e6ae69..e7fa703c8d5e 100644
--- a/arch/arc/kernel/head.S
+++ b/arch/arc/kernel/head.S
@@ -50,28 +50,37 @@
 .endm
 
         .section .init.text, "ax",@progbits
-        .type stext, @function
-        .globl stext
-stext:
-        ;-------------------------------------------------------------------
-        ; Don't clobber r0-r2 yet. It might have bootloader provided info
-        ;-------------------------------------------------------------------
+
+;----------------------------------------------------------------
+; Default Reset Handler (jumped into from Reset vector)
+; - Don't clobber r0,r1,r2 as they might have u-boot provided args
+; - Platforms can override this weak version if needed
+;----------------------------------------------------------------
+WEAK(res_service)
+        j       stext
+END(res_service)
+
+;----------------------------------------------------------------
+; Kernel Entry point
+;----------------------------------------------------------------
+ENTRY(stext)
 
         CPU_EARLY_SETUP
 
 #ifdef CONFIG_SMP
-        ; Ensure Boot (Master) proceeds. Others wait in platform dependent way
-        ;       IDENTITY Reg [ 3  2  1  0 ]
-        ;       (cpu-id)             ^^^        => Zero for UP ARC700
-        ;                                       => #Core-ID if SMP (Master 0)
-        ; Note that non-boot CPUs might not land here if halt-on-reset and
-        ; instead breath life from @first_lines_of_secondary, but we still
-        ; need to make sure only boot cpu takes this path.
         GET_CPU_ID  r5
         cmp     r5, 0
-        mov.ne  r0, r5
-        jne     arc_platform_smp_wait_to_boot
+        mov.nz  r0, r5
+#ifdef CONFIG_ARC_SMP_HALT_ON_RESET
+        ; Non-Master can proceed as system would be booted sufficiently
+        jnz     first_lines_of_secondary
+#else
+        ; Non-Masters wait for Master to boot enough and bring them up
+        jnz     arc_platform_smp_wait_to_boot
+#endif
+        ; Master falls thru
 #endif
+
         ; Clear BSS before updating any globals
         ; XXX: use ZOL here
         mov     r5, __bss_start
@@ -102,16 +111,14 @@ stext:
         GET_TSK_STACK_BASE r9, sp       ; r9 = tsk, sp = stack base(output)
 
         j       start_kernel    ; "C" entry point
+END(stext)
 
 #ifdef CONFIG_SMP
 ;----------------------------------------------------------------
 ;     First lines of code run by secondary before jumping to 'C'
 ;----------------------------------------------------------------
         .section .text, "ax",@progbits
-        .type first_lines_of_secondary, @function
-        .globl first_lines_of_secondary
-
-first_lines_of_secondary:
+ENTRY(first_lines_of_secondary)
 
         CPU_EARLY_SETUP
 
@@ -126,5 +133,5 @@ first_lines_of_secondary:
         GET_TSK_STACK_BASE r0, sp
 
         j       start_kernel_secondary
-
+END(first_lines_of_secondary)
 #endif
diff --git a/arch/arc/kernel/vmlinux.lds.S b/arch/arc/kernel/vmlinux.lds.S
index dd35bde39f69..894e696bddaa 100644
--- a/arch/arc/kernel/vmlinux.lds.S
+++ b/arch/arc/kernel/vmlinux.lds.S
@@ -12,7 +12,7 @@
 #include <asm/thread_info.h>
 
 OUTPUT_ARCH(arc)
-ENTRY(_stext)
+ENTRY(res_service)
 
 #ifdef CONFIG_CPU_BIG_ENDIAN
 jiffies = jiffies_64 + 4;