ARC updates for 5.8-rc5

- User build systems to pass -mcpu
 
  - Fix potential EFA clobber in syscall handler
 
  - Fix ARCompact 2 levels of interrupts build
 
  - Detect newer HS CPU releases
 
  - miscll other fixes
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Merge tag 'arc-5.8-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc

Pull ARC fixes from Vineet Gupta:

 - User build systems to pass -mcpu

 - Fix potential EFA clobber in syscall handler

 - Fix ARCompact 2 levels of interrupts build

 - Detect newer HS CPU releases

 - misc other fixes

* tag 'arc-5.8-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc:
  ARCv2: support loop buffer (LPB) disabling
  ARC: build: remove deprecated toggle for arc700 builds
  ARC: build: allow users to specify -mcpu
  ARCv2: boot log: detect newer/upconing HS3x/HS4x releases
  ARC: elf: use right ELF_ARCH
  ARC: [arcompact] fix bitrot with 2 levels of interrupt
  ARC: entry: fix potential EFA clobber when TIF_SYSCALL_TRACE

arch/arc/Kconfig

@@ -170,6 +170,15 @@ config ARC_CPU_HS
 
 endchoice
 
+config ARC_TUNE_MCPU
+	string "Override default -mcpu compiler flag"
+	default ""
+	help
+	  Override default -mcpu=xxx compiler flag (which is set depending on
+	  the ISA version) with the specified value.
+	  NOTE: If specified flag isn't supported by current compiler the
+	  ISA default value will be used as a fallback.
+
 config CPU_BIG_ENDIAN
 	bool "Enable Big Endian Mode"
 	help
@@ -465,6 +474,12 @@ config ARC_IRQ_NO_AUTOSAVE
 	  This is programmable and can be optionally disabled in which case
 	  software INTERRUPT_PROLOGUE/EPILGUE do the needed work
 
+config ARC_LPB_DISABLE
+	bool "Disable loop buffer (LPB)"
+	help
+	  On HS cores, loop buffer (LPB) is programmable in runtime and can
+	  be optionally disabled.
+
 endif # ISA_ARCV2
 
 endmenu   # "ARC CPU Configuration"

arch/arc/Makefile

@@ -10,8 +10,25 @@ CROSS_COMPILE := $(call cc-cross-prefix, arc-linux- arceb-linux-)
 endif
 
 cflags-y	+= -fno-common -pipe -fno-builtin -mmedium-calls -D__linux__
-cflags-$(CONFIG_ISA_ARCOMPACT)	+= -mA7
+
-cflags-$(CONFIG_ISA_ARCV2)	+= -mcpu=hs38
+tune-mcpu-def-$(CONFIG_ISA_ARCOMPACT)	:= -mcpu=arc700
+tune-mcpu-def-$(CONFIG_ISA_ARCV2)	:= -mcpu=hs38
+
+ifeq ($(CONFIG_ARC_TUNE_MCPU),"")
+cflags-y				+= $(tune-mcpu-def-y)
+else
+tune-mcpu				:= $(shell echo $(CONFIG_ARC_TUNE_MCPU))
+tune-mcpu-ok 				:= $(call cc-option-yn, $(tune-mcpu))
+ifeq ($(tune-mcpu-ok),y)
+cflags-y				+= $(tune-mcpu)
+else
+# The flag provided by 'CONFIG_ARC_TUNE_MCPU' option isn't known by this compiler
+# (probably the compiler is too old). Use ISA default mcpu flag instead as a safe option.
+$(warning ** WARNING ** CONFIG_ARC_TUNE_MCPU flag '$(tune-mcpu)' is unknown, fallback to '$(tune-mcpu-def-y)')
+cflags-y				+= $(tune-mcpu-def-y)
+endif
+endif
+
 
 ifdef CONFIG_ARC_CURR_IN_REG
 # For a global register defintion, make sure it gets passed to every file

arch/arc/include/asm/elf.h

@@ -19,7 +19,7 @@
 #define  R_ARC_32_PCREL		0x31
 
 /*to set parameters in the core dumps */
-#define ELF_ARCH		EM_ARCOMPACT
+#define ELF_ARCH		EM_ARC_INUSE
 #define ELF_CLASS		ELFCLASS32
 
 #ifdef CONFIG_CPU_BIG_ENDIAN

arch/arc/include/asm/irqflags-compact.h

@@ -90,6 +90,9 @@ static inline void arch_local_irq_restore(unsigned long flags)
 /*
  * Unconditionally Enable IRQs
  */
+#ifdef CONFIG_ARC_COMPACT_IRQ_LEVELS
+extern void arch_local_irq_enable(void);
+#else
 static inline void arch_local_irq_enable(void)
 {
 	unsigned long temp;
@@ -102,7 +105,7 @@ static inline void arch_local_irq_enable(void)
 	: "n"((STATUS_E1_MASK | STATUS_E2_MASK))
 	: "cc", "memory");
 }
-
+#endif
 
 /*
  * Unconditionally Disable IRQs

arch/arc/kernel/entry.S

@@ -165,7 +165,6 @@ END(EV_Extension)
 tracesys:
 	; save EFA in case tracer wants the PC of traced task
 	; using ERET won't work since next-PC has already committed
-	lr  r12, [efa]
 	GET_CURR_TASK_FIELD_PTR   TASK_THREAD, r11
 	st  r12, [r11, THREAD_FAULT_ADDR]	; thread.fault_address
 
@@ -208,15 +207,9 @@ tracesys_exit:
 ; Breakpoint TRAP
 ; ---------------------------------------------
 trap_with_param:
-
+	mov r0, r12	; EFA in case ptracer/gdb wants stop_pc
-	; stop_pc info by gdb needs this info
-	lr  r0, [efa]
 	mov r1, sp
 
-	; Now that we have read EFA, it is safe to do "fake" rtie
-	;   and get out of CPU exception mode
-	FAKE_RET_FROM_EXCPN
-
 	; Save callee regs in case gdb wants to have a look
 	; SP will grow up by size of CALLEE Reg-File
 	; NOTE: clobbers r12
@@ -243,6 +236,10 @@ ENTRY(EV_Trap)
 
 	EXCEPTION_PROLOGUE
 
+	lr  r12, [efa]
+
+	FAKE_RET_FROM_EXCPN
+
 	;============ TRAP 1   :breakpoints
 	; Check ECR for trap with arg (PROLOGUE ensures r10 has ECR)
 	bmsk.f 0, r10, 7
@@ -250,9 +247,6 @@ ENTRY(EV_Trap)
 
 	;============ TRAP  (no param): syscall top level
 
-	; First return from Exception to pure K mode (Exception/IRQs renabled)
-	FAKE_RET_FROM_EXCPN
-
 	; If syscall tracing ongoing, invoke pre-post-hooks
 	GET_CURR_THR_INFO_FLAGS   r10
 	btst r10, TIF_SYSCALL_TRACE

arch/arc/kernel/head.S

@@ -59,6 +59,14 @@
 	bclr	r5, r5, STATUS_AD_BIT
 #endif
 	kflag	r5
+
+#ifdef CONFIG_ARC_LPB_DISABLE
+	lr	r5, [ARC_REG_LPB_BUILD]
+	breq    r5, 0, 1f		; LPB doesn't exist
+	mov	r5, 1
+	sr	r5, [ARC_REG_LPB_CTRL]
+1:
+#endif /* CONFIG_ARC_LPB_DISABLE */
 #endif
 	; Config DSP_CTRL properly, so kernel may use integer multiply,
 	; multiply-accumulate, and divide operations

arch/arc/kernel/setup.c

@@ -58,10 +58,12 @@ static const struct id_to_str arc_legacy_rel[] = {
 	{ 0x00,		NULL   }
 };
 
-static const struct id_to_str arc_cpu_rel[] = {
+static const struct id_to_str arc_hs_ver54_rel[] = {
 	/* UARCH.MAJOR,	Release */
 	{  0,		"R3.10a"},
 	{  1,		"R3.50a"},
+	{  2,		"R3.60a"},
+	{  3,		"R4.00a"},
 	{  0xFF,	NULL   }
 };
 
@@ -117,12 +119,6 @@ static void decode_arc_core(struct cpuinfo_arc *cpu)
 	struct bcr_uarch_build_arcv2 uarch;
 	const struct id_to_str *tbl;
 
-	/*
-	 * Up until (including) the first core4 release (0x54) things were
-	 * simple: AUX IDENTITY.ARCVER was sufficient to identify arc family
-	 * and release: 0x50 to 0x53 was HS38, 0x54 was HS48 (dual issue)
-	 */
-
 	if (cpu->core.family < 0x54) { /* includes arc700 */
 
 		for (tbl = &arc_legacy_rel[0]; tbl->id != 0; tbl++) {
@@ -143,11 +139,10 @@ static void decode_arc_core(struct cpuinfo_arc *cpu)
 	}
 
 	/*
-	 * However the subsequent HS release (same 0x54) allow HS38 or HS48
+	 * Initial HS cores bumped AUX IDENTITY.ARCVER for each release until
-	 * configurations and encode this info in a different BCR.
+	 * ARCVER 0x54 which introduced AUX MICRO_ARCH_BUILD and subsequent
-	 * The BCR was introduced in 0x54 so can't be read unconditionally.
+	 * releases only update it.
 	 */
-
 	READ_BCR(ARC_REG_MICRO_ARCH_BCR, uarch);
 
 	if (uarch.prod == 4) {
@@ -158,7 +153,7 @@ static void decode_arc_core(struct cpuinfo_arc *cpu)
 		cpu->name = "HS38";
 	}
 
-	for (tbl = &arc_cpu_rel[0]; tbl->id != 0xFF; tbl++) {
+	for (tbl = &arc_hs_ver54_rel[0]; tbl->id != 0xFF; tbl++) {
 		if (uarch.maj == tbl->id) {
 			cpu->release = tbl->str;
 			break;