2nd round of ARC udpates for 4.10rc1

- Fix for aliasing VIPT dcache in old ARC700 cores
 
  - micro-optimization in ARC700 ProtV handler
 
  - Enable SG_CHAIN  [Vladimir]
 
  - ARC HS38 core intc default to prio 1
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Merge tag 'arc-4.10-rc1-part2' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc

Pull more ARC updates from Vineet Gupta:

 - Fix for aliasing VIPT dcache in old ARC700 cores

 - micro-optimization in ARC700 ProtV handler

 - Enable SG_CHAIN  [Vladimir]

 - ARC HS38 core intc default to prio 1

* tag 'arc-4.10-rc1-part2' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc:
  ARC: mm: arc700: Don't assume 2 colours for aliasing VIPT dcache
  ARC: mm: No need to save cache version in @cpuinfo
  ARC: enable SG chaining
  ARCv2: intc: default all interrupts to priority 1
  ARCv2: entry: document intr disable in hard isr
  ARC: ARCompact entry: elide re-reading ECR in ProtV handler

Documentation/features/io/sg-chain/arch-support.txt

@@ -7,7 +7,7 @@
     |         arch |status|
     -----------------------
     |       alpha: | TODO |
-    |         arc: | TODO |
+    |         arc: |  ok  |
     |         arm: |  ok  |
     |       arm64: |  ok  |
     |       avr32: | TODO |

arch/arc/Kconfig

@@ -9,6 +9,7 @@
 config ARC
 	def_bool y
 	select ARC_TIMERS
+	select ARCH_HAS_SG_CHAIN
 	select ARCH_SUPPORTS_ATOMIC_RMW if ARC_HAS_LLSC
 	select BUILDTIME_EXTABLE_SORT
 	select CLONE_BACKWARDS

arch/arc/include/asm/arcregs.h

@@ -244,7 +244,7 @@ struct cpuinfo_arc_mmu {
 };
 
 struct cpuinfo_arc_cache {
-	unsigned int sz_k:14, line_len:8, assoc:4, ver:4, alias:1, vipt:1;
+	unsigned int sz_k:14, line_len:8, assoc:4, alias:1, vipt:1, pad:4;
 };
 
 struct cpuinfo_arc_bpu {

arch/arc/include/asm/cacheflush.h

@@ -85,6 +85,10 @@ void flush_anon_page(struct vm_area_struct *vma,
  */
 #define PG_dc_clean	PG_arch_1
 
+#define CACHE_COLORS_NUM	4
+#define CACHE_COLORS_MSK	(CACHE_COLORS_NUM - 1)
+#define CACHE_COLOR(addr)	(((unsigned long)(addr) >> (PAGE_SHIFT)) & CACHE_COLORS_MSK)
+
 /*
  * Simple wrapper over config option
  * Bootup code ensures that hardware matches kernel configuration
@@ -94,8 +98,6 @@ static inline int cache_is_vipt_aliasing(void)
 	return IS_ENABLED(CONFIG_ARC_CACHE_VIPT_ALIASING);
 }
 
-#define CACHE_COLOR(addr)	(((unsigned long)(addr) >> (PAGE_SHIFT)) & 1)
-
 /*
  * checks if two addresses (after page aligning) index into same cache set
  */

arch/arc/include/asm/irqflags-arcv2.h

@@ -38,10 +38,10 @@
 #define AUX_IRQ_ACT_BIT_U	31
 
 /*
- * User space should be interruptable even by lowest prio interrupt
- * Safe even if actual interrupt priorities is fewer or even one
+ * Hardware supports 16 priorities (0 highest, 15 lowest)
+ * Linux by default runs at 1, priority 0 reserved for NMI style interrupts
  */
-#define ARCV2_IRQ_DEF_PRIO	15
+#define ARCV2_IRQ_DEF_PRIO	1
 
 /* seed value for status register */
 #define ISA_INIT_STATUS_BITS	(STATUS_IE_MASK | STATUS_AD_MASK | \

arch/arc/kernel/entry-arcv2.S

@@ -67,12 +67,23 @@ ENTRY(handle_interrupt)
 
 	INTERRUPT_PROLOGUE  irq
 
-	clri		; To make status32.IE agree with CPU internal state
+	# irq control APIs local_irq_save/restore/disable/enable fiddle with
+	# global interrupt enable bits in STATUS32 (.IE for 1 prio, .E[] for 2 prio)
+	# However a taken interrupt doesn't clear these bits. Thus irqs_disabled()
+	# query in hard ISR path would return false (since .IE is set) which would
+	# trips genirq interrupt handling asserts.
+	#
+	# So do a "soft" disable of interrutps here.
+	#
+	# Note this disable is only for consistent book-keeping as further interrupts
+	# will be disabled anyways even w/o this. Hardware tracks active interrupts
+	# seperately in AUX_IRQ_ACTIVE.active and will not take new interrupts
+	# unless this one returns (or higher prio becomes pending in 2-prio scheme)
 
-#ifdef CONFIG_TRACE_IRQFLAGS
-	TRACE_ASM_IRQ_DISABLE
-#endif
+	IRQ_DISABLE
 
+	; icause is banked: one per priority level
+	; so a higher prio interrupt taken here won't clobber prev prio icause
 	lr  r0, [ICAUSE]
 	mov   blink, ret_from_exception
 
@@ -171,6 +182,7 @@ END(EV_TLBProtV)
 ; All 2 entry points to here already disable interrupts
 
 .Lrestore_regs:
+restore_regs:
 
 	# Interrpts are actually disabled from this point on, but will get
 	# reenabled after we return from interrupt/exception.

arch/arc/kernel/entry-compact.S

@@ -259,7 +259,7 @@ ENTRY(EV_TLBProtV)
 
 	EXCEPTION_PROLOGUE
 
-	lr  r2, [ecr]
+	mov r2, r9	; ECR set into r9 already
 	lr  r0, [efa]	; Faulting Data address (not part of pt_regs saved above)
 
 	; Exception auto-disables further Intr/exceptions.

arch/arc/kernel/intc-arcv2.c

@@ -14,8 +14,6 @@
 #include <linux/irqchip.h>
 #include <asm/irq.h>
 
-static int irq_prio;
-
 /*
  * Early Hardware specific Interrupt setup
  * -Called very early (start_kernel -> setup_arch -> setup_processor)
@@ -24,7 +22,7 @@ static int irq_prio;
  */
 void arc_init_IRQ(void)
 {
-	unsigned int tmp;
+	unsigned int tmp, irq_prio;
 
 	struct irq_build {
 #ifdef CONFIG_CPU_BIG_ENDIAN
@@ -67,12 +65,12 @@ void arc_init_IRQ(void)
 
 	irq_prio = irq_bcr.prio;	/* Encoded as N-1 for N levels */
 	pr_info("archs-intc\t: %d priority levels (default %d)%s\n",
-		irq_prio + 1, irq_prio,
+		irq_prio + 1, ARCV2_IRQ_DEF_PRIO,
 		irq_bcr.firq ? " FIRQ (not used)":"");
 
 	/* setup status32, don't enable intr yet as kernel doesn't want */
 	tmp = read_aux_reg(0xa);
-	tmp |= STATUS_AD_MASK | (irq_prio << 1);
+	tmp |= STATUS_AD_MASK | (ARCV2_IRQ_DEF_PRIO << 1);
 	tmp &= ~STATUS_IE_MASK;
 	asm volatile("kflag %0	\n"::"r"(tmp));
 }
@@ -93,7 +91,7 @@ void arcv2_irq_enable(struct irq_data *data)
 {
 	/* set default priority */
 	write_aux_reg(AUX_IRQ_SELECT, data->irq);
-	write_aux_reg(AUX_IRQ_PRIORITY, irq_prio);
+	write_aux_reg(AUX_IRQ_PRIORITY, ARCV2_IRQ_DEF_PRIO);
 
 	/*
 	 * hw auto enables (linux unmask) all by default

arch/arc/mm/cache.c

@@ -40,7 +40,7 @@ char *arc_cache_mumbojumbo(int c, char *buf, int len)
 	struct cpuinfo_arc_cache *p;
 
 #define PR_CACHE(p, cfg, str)						\
-	if (!(p)->ver)							\
+	if (!(p)->line_len)						\
 		n += scnprintf(buf + n, len - n, str"\t\t: N/A\n");	\
 	else								\
 		n += scnprintf(buf + n, len - n,			\
@@ -54,7 +54,7 @@ char *arc_cache_mumbojumbo(int c, char *buf, int len)
 	PR_CACHE(&cpuinfo_arc700[c].dcache, CONFIG_ARC_HAS_DCACHE, "D-Cache");
 
 	p = &cpuinfo_arc700[c].slc;
-	if (p->ver)
+	if (p->line_len)
 		n += scnprintf(buf + n, len - n,
 			       "SLC\t\t: %uK, %uB Line%s\n",
 			       p->sz_k, p->line_len, IS_USED_RUN(slc_enable));
@@ -104,7 +104,6 @@ static void read_decode_cache_bcr_arcv2(int cpu)
 	READ_BCR(ARC_REG_SLC_BCR, sbcr);
 	if (sbcr.ver) {
 		READ_BCR(ARC_REG_SLC_CFG, slc_cfg);
-		p_slc->ver = sbcr.ver;
 		p_slc->sz_k = 128 << slc_cfg.sz;
 		l2_line_sz = p_slc->line_len = (slc_cfg.lsz == 0) ? 128 : 64;
 	}
@@ -152,7 +151,6 @@ void read_decode_cache_bcr(void)
 
 	p_ic->line_len = 8 << ibcr.line_len;
 	p_ic->sz_k = 1 << (ibcr.sz - 1);
-	p_ic->ver = ibcr.ver;
 	p_ic->vipt = 1;
 	p_ic->alias = p_ic->sz_k/p_ic->assoc/TO_KB(PAGE_SIZE) > 1;
 
@@ -176,7 +174,6 @@ dc_chk:
 
 	p_dc->line_len = 16 << dbcr.line_len;
 	p_dc->sz_k = 1 << (dbcr.sz - 1);
-	p_dc->ver = dbcr.ver;
 
 slc_chk:
 	if (is_isa_arcv2())
@@ -945,17 +942,13 @@ void arc_cache_init(void)
 	if (IS_ENABLED(CONFIG_ARC_HAS_ICACHE)) {
 		struct cpuinfo_arc_cache *ic = &cpuinfo_arc700[cpu].icache;
 
-		if (!ic->ver)
+		if (!ic->line_len)
 			panic("cache support enabled but non-existent cache\n");
 
 		if (ic->line_len != L1_CACHE_BYTES)
 			panic("ICache line [%d] != kernel Config [%d]",
 			      ic->line_len, L1_CACHE_BYTES);
 
-		if (ic->ver != CONFIG_ARC_MMU_VER)
-			panic("Cache ver [%d] doesn't match MMU ver [%d]\n",
-			      ic->ver, CONFIG_ARC_MMU_VER);
-
 		/*
 		 * In MMU v4 (HS38x) the aliasing icache config uses IVIL/PTAG
 		 * pair to provide vaddr/paddr respectively, just as in MMU v3
@@ -969,7 +962,7 @@ void arc_cache_init(void)
 	if (IS_ENABLED(CONFIG_ARC_HAS_DCACHE)) {
 		struct cpuinfo_arc_cache *dc = &cpuinfo_arc700[cpu].dcache;
 
-		if (!dc->ver)
+		if (!dc->line_len)
 			panic("cache support enabled but non-existent cache\n");
 
 		if (dc->line_len != L1_CACHE_BYTES)
@@ -979,11 +972,16 @@ void arc_cache_init(void)
 		/* check for D-Cache aliasing on ARCompact: ARCv2 has PIPT */
 		if (is_isa_arcompact()) {
 			int handled = IS_ENABLED(CONFIG_ARC_CACHE_VIPT_ALIASING);
+			int num_colors = dc->sz_k/dc->assoc/TO_KB(PAGE_SIZE);
 
-			if (dc->alias && !handled)
-				panic("Enable CONFIG_ARC_CACHE_VIPT_ALIASING\n");
-			else if (!dc->alias && handled)
+			if (dc->alias) {
+				if (!handled)
+					panic("Enable CONFIG_ARC_CACHE_VIPT_ALIASING\n");
+				if (CACHE_COLORS_NUM != num_colors)
+					panic("CACHE_COLORS_NUM not optimized for config\n");
+			} else if (!dc->alias && handled) {
 				panic("Disable CONFIG_ARC_CACHE_VIPT_ALIASING\n");
+			}
 		}
 	}