ARC: enable uboot support unconditionally

After reworking U-boot args handling code and adding paranoid
arguments check we can eliminate CONFIG_ARC_UBOOT_SUPPORT and
enable uboot support unconditionally.

For JTAG case we can assume that core registers will come up
reset value of 0 or in worst case we rely on user passing
'-on=clear_regs' to Metaware debugger.

Cc: stable@vger.kernel.org
Tested-by: NCorentin LABBE <clabbe@baylibre.com>
Signed-off-by: NEugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

arch/arc/Kconfig

@@ -191,7 +191,6 @@ config NR_CPUS
 
 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
@@ -523,17 +522,6 @@ config ARC_DBG_TLB_PARANOIA
 
 endif
 
-config ARC_UBOOT_SUPPORT
-	bool "Support uboot arg Handling"
-	help
-	  ARC Linux by default checks for uboot provided args as pointers to
-	  external cmdline or DTB. This however breaks in absence of uboot,
-	  when booting from Metaware debugger directly, as the registers are
-	  not zeroed out on reset by mdb and/or ARCv2 based cores. The bogus
-	  registers look like uboot args to kernel which then chokes.
-	  So only enable the uboot arg checking/processing if users are sure
-	  of uboot being in play.
-
 config ARC_BUILTIN_DTB_NAME
 	string "Built in DTB"
 	help

arch/arc/configs/nps_defconfig

@@ -31,7 +31,6 @@ CONFIG_ARC_CACHE_LINE_SHIFT=5
 # CONFIG_ARC_HAS_LLSC is not set
 CONFIG_ARC_KVADDR_SIZE=402
 CONFIG_ARC_EMUL_UNALIGNED=y
-CONFIG_ARC_UBOOT_SUPPORT=y
 CONFIG_PREEMPT=y
 CONFIG_NET=y
 CONFIG_UNIX=y

arch/arc/configs/vdk_hs38_defconfig

@@ -13,7 +13,6 @@ CONFIG_PARTITION_ADVANCED=y
 CONFIG_ARC_PLAT_AXS10X=y
 CONFIG_AXS103=y
 CONFIG_ISA_ARCV2=y
-CONFIG_ARC_UBOOT_SUPPORT=y
 CONFIG_ARC_BUILTIN_DTB_NAME="vdk_hs38"
 CONFIG_PREEMPT=y
 CONFIG_NET=y

arch/arc/configs/vdk_hs38_smp_defconfig

@@ -15,8 +15,6 @@ CONFIG_AXS103=y
 CONFIG_ISA_ARCV2=y
 CONFIG_SMP=y
 # CONFIG_ARC_TIMERS_64BIT is not set
-# CONFIG_ARC_SMP_HALT_ON_RESET is not set
-CONFIG_ARC_UBOOT_SUPPORT=y
 CONFIG_ARC_BUILTIN_DTB_NAME="vdk_hs38_smp"
 CONFIG_PREEMPT=y
 CONFIG_NET=y

arch/arc/kernel/head.S

@@ -100,7 +100,6 @@ ENTRY(stext)
 	st.ab   0, [r5, 4]
 1:
 
-#ifdef CONFIG_ARC_UBOOT_SUPPORT
 	; Uboot - kernel ABI
 	;    r0 = [0] No uboot interaction, [1] cmdline in r2, [2] DTB in r2
 	;    r1 = magic number (always zero as of now)
@@ -108,7 +107,6 @@ ENTRY(stext)
 	; These are handled later in handle_uboot_args()
 	st	r0, [@uboot_tag]
 	st	r2, [@uboot_arg]
-#endif
 
 	; setup "current" tsk and optionally cache it in dedicated r25
 	mov	r9, @init_task

arch/arc/kernel/setup.c

@@ -487,7 +487,6 @@ void __init handle_uboot_args(void)
 	bool use_embedded_dtb = true;
 	bool append_cmdline = false;
 
-#ifdef CONFIG_ARC_UBOOT_SUPPORT
 	/* check that we know this tag */
 	if (uboot_tag != UBOOT_TAG_NONE &&
 	    uboot_tag != UBOOT_TAG_CMDLINE &&
@@ -514,7 +513,6 @@ void __init handle_uboot_args(void)
 		append_cmdline = true;
 
 ignore_uboot_args:
-#endif
 
 	if (use_embedded_dtb) {
 		machine_desc = setup_machine_fdt(__dtb_start);